Course: Family Medicine Clerkship Topic: Usmle
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Question # 1
Select the single best answer to the numbered question.
A 50 year old female with a ten year history of type II diabetes presents for regularly-scheduled follow up. She has no complaints, and just visited her ophthalmologist last week.
Current medications include glyburide, metformin, and simvastatin. On physical exam, vital signs are virtually unchanged from previous visits, with temperature 37.1 C (99 F), HR
80, BP 140/83, RR 15, and O2 Sat 98% on room air. Neurological examination reveals diminished sensation to light touch and pinprick in a stocking distribution on the lower
extremities bilaterally. Remainder of physical exam is benign. Laboratory evaluation reveals: Na+ 136, K+ 3.9 Cl- 104, HCO3- 25, BUN 15, Cr 1.0, Glucose 150; hemoglobin A1c:
7.1%; Urinalysis: negative for ketones, glucose, bilirubin, leukocyte esterase, or blood; moderate protein; Lipid profile: Total cholesterol 146, HDL 46, LDL 100. At this time, which of
the following would be the most appropriate intervention?
A. Increase simvastatin
B. Increase glyburide
C. Increase metformin
D. Add hydrochlorothiazide
E. Add lisinopril
You answered: E
Explanations:
A. The patient’s lipid profile is technically at her target LDL – thus, she does not need an increase in her statin (answer A). Under the current ATP III guidelines, patients with diabetes are considered to have known coronary
heart disease, and therefore have a target LDL of less than 100. To review the ATP III lipid guidelines at a glance, check out http://www.nhlbi.nih.gov/guidelines/cholesterol/atglance.pdf HOWEVER, please note that
although the official guideline is still LDL <100, that figure is likely to change in the future, because new evidence has come out showing that lower LDLs (<70) are better... so in the near future, this question may have two
correct answers!
B. Either increasing glyburide (answer B) or increasing metformin (answer C) would be helpful for reducing the patient’s blood sugar and better controlling her diabetes. However, her most recent Hgb A1c was not that bad –
remember that the goal for diabetic patients is less than 7.0%. For more on Hgb A1c, including how to correlate the test result with the patient’s average blood glucose, check out Diabetes Care 2002;25:275-8 or
http://www.metrika.com/3medical/hemoglobin-m.html.
C. Either increasing glyburide (answer B) or increasing metformin (answer C) would be helpful for reducing the patient’s blood sugar and better controlling her diabetes. However, her most recent Hgb A1c was not that bad –
remember that the goal for diabetic patients is less than 7.0%. For more on Hgb A1c, including how to correlate the test result with the patient’s average blood glucose, check out Diabetes Care 2002;25:275-8 or
http://www.metrika.com/3medical/hemoglobin-m.html.
D. Adding hydrochlorothiazide (answer D) could improve her hypertension, and would be a reasonable first-line antihypertensive in a patient without diabetes. It is worth noting that this patient IS hypertensive – all diabetics
should have a systolic blood pressure of less than 130. Still, diabetic patients have a compelling reason to begin antihypertensive therapy with ACE inhibitors or ARBs, however, due to the reno-protective effects of these
drugs.
E. Key teaching point: All diabetics should be on an ACE inhibitor or ARB for cardiovascular and renal protection. This is a dense question stem, but the important things to note are that this is a patient with type II diabetes
who also has proteinuria and elevated blood pressure. Since her medication list does not include any mention of an ACE inhibitor or ARB, beginning one at this time would be the appropriate next step in management
(answer E). As it turns out, microalbuminuria is a risk factor for both cardiovascular disease and progression of renal disease to ESRD and dialysis – and this patient already has macroalbuminuria, since dipsticks are not
sensitive enough to pick up small amounts of protein! ACE inhibitors and ARBs have been shown to reduce these outcomes – even in normotensive diabetics. All diabetics, therefore, should be on an ACE inhibitor or
ARB. Since this patient is hypertensive as well, she has all the more reason to begin a medication such as lisinopril. (It is, however, also important to note that the diagnosis of hypertension should not be made on the
basis of a single blood pressure measurement in a physician’s office. In this case, the question stem mentions that her vital signs have been similar to those recorded in the past, so making a diagnosis of hypertension is
more acceptable. Additionally, diabetics have a target blood pressure of systolic less than 130 mm Hg, a more stringent guideline than for non-diabetic patients.) As an additional teaching point, every health maintenance
visit with a diabetic patient should focus on the “Diabetic Five” – these five things, in this order: 1) Smoking cessation 2) Blood pressure control 3) Lipid control 4) Aspirin/metformin 5) Glucose control Adding
hydrochlorothiazide (answer D) could improve her hypertension, and would be a reasonable first-line antihypertensive in a patient without diabetes. It is worth noting that this patient IS hypertensive – all diabetics should
have a systolic blood pressure of less than 130. Still, diabetic patients have a compelling reason to begin antihypertensive therapy with ACE inhibitors or ARBs, however, due to the reno-protective effects of these drugs
mentioned above. Either increasing glyburide (answer B) or increasing metformin (answer C) would be helpful for reducing the patient’s blood sugar and better controlling her diabetes. However, her most recent Hgb A1c
was not that bad – remember that the goal for diabetic patients is less than 7.0%. For more on Hgb A1c, including how to correlate the test result with the patient’s average blood glucose, check out Diabetes Care
2002;25:275-8 or http://www.metrika.com/3medical/hemoglobin-m.html. Similarly, the patient’s lipid profile is at her target LDL – thus, she does not need an increase in her statin (answer A). Under the ATP III guidelines,
patients with diabetes are considered to have known coronary heart disease, and therefore have a target LDL of less than 100. To review the ATP III lipid guidelines at a glance, check out
http://www.nhlbi.nih.gov/guidelines/cholesterol/atglance.pdf For an overview of diabetic nephropathy, try Ritz E., Orth S. R. Primary Care: Nephropathy in Patients with Diabetes Mellitus. N Engl J Med 1999; 341:1127-
1133, Oct 7, 1999. http://content.nejm.org/cgi/reprint/341/15/1127.pdf?
hits=20&where=fulltext&andorexactfulltext=and&searchterm=diabetes&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&excludeflag=TWEEK_element&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
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Question # 2
Select the single best answer to the numbered question.
A 55 year old female comes to the emergency department complaining of a headache for the past six hours. Her headache began abruptly after she finished eating breakfast, and
quickly increased to 8/10 throbbing pain located mainly over her right temple. The pain has been associated with mild nausea but no vomiting. She denies chronic or recurrent
headaches, but did have one headache similar to this one two weeks ago, which resolved after taking ibuprofen and lying in a quiet, dark room. She has smoked one pack of
cigarettes daily for 38 years. On physical exam, the patient has temperature of 37.0 C (98.6 F), pulse of 99, and BP 147/95. Neurological examination is nonfocal, but mild
photophobia and nuchal rigidity are noted. Fundoscopic examination reveals no papilledema. Skin exam shows no lesions. CT of the head, obtained without contrast, reveals no
abnormalities. What is the most appropriate next step in the management of this patient?
A. Obtain head CT with contrast
B. Lumbar puncture
C. Administer i.m. sumatriptan
D. Administer oral ibuprofen
E. Administer i.v. ceftriaxone
You did not answer this question.
Explanations:
A. CT with contrast (answer A) might help you identify a space-occupying lesion, such as a tumor - which can certainly be a cause of headache. However, such lesions are not likely to cause a
sudden onset headache such as the one described in the question stem. Remember that CT without contrast is the best study to identify an acute head bleed, whether you’re looking for a stroke,
a hematoma, or a hemorrhage.
B. No explanation provided.
C. Sumatriptan injection (answer C) would be a fine choice if the patient were having a migraine. Migraine headache pain does lateralize in 60-70% of patients, may be associated with photophobia
or nausea, and be relieved by NSAIDs or lying in a dark room. However, most patients with migraine have their first symptoms in adolescence or early adulthood. A new-onset migraine in a
patient 55 years old would be very unusual. (It is important to recognize that the patient’s headache two weeks ago was likely a “sentinel bleed” from an aneurysm.) Additionally, migraines are
frequently associated with sensory “auras” such as visual scotomata or paresthesias.
D. Ibuprofen (answer D) is a reasonable first-line treatment for a patient with a tension headache. These headaches are typically bilateral, and would seldom become intense enough to necessitate
a visit to the ER.
E. Ceftriaxone (answer E) is the most commonly used empiric antibiotic for adults with suspected bacterial meningitis since it penetrates the CSF and covers the most likely pathogens in this age
group: S. pneumoniae (60%) and N. meningitides (20%). This patient is afebrile, however, and her stiff neck and photophobia are simply signs of meningeal irritation – which in this case is
caused by SAH, not a bacterial infection. Meningitis may cause headache, but not as suddenly as the headache described in the question. Even if this patient was suspected to have meningitis,
you would likely want to obtain an LP before giving antibiotics so that you don’t sterilize the cultures! After obtaining an LP, antibiotic therapy with ceftriaxone (or cefotaxime) and vancomycin
could be started. (The latter is used to cover the possibility of drug-resistant S. pneumoniae while you await results of the CSF culture.)
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Question # 3
Select the single best answer to the numbered question.
A four week old male infant is brought by his mother to the physician following one week of emesis. The patient’s mother states that the patient has been vomiting non-bilious
material immediately after each feeding, but then becomes fussy and demands to be fed again. She denies ever seeing any blood in the emesis. Over the past two or three days,
the infant’s vomiting has become increasingly sudden and forceful. The child is irritable, with few tears. The oropharynx is dry, the infant’s fontanelles appear sunken, and moderate
skin tenting is noted. Capillary refill is approximately 2 seconds. On abdominal exam, visible peristaltic waves are observed, and a 1cm firm mass is palpated in the right upper
quadrant. What is the most likely laboratory finding?
A. Na+ 130, K+ 2.9, Cl- 89, HCO3- 35
B. Na+ 138, K+ 3.8, Cl- 100, HCO3- 26
, B. Na+ 138, K+ 3.8, Cl- 100, HCO3- 26
C. Na+ 150, K+ 4.0, Cl- 100, HCO3- 24
D. Na+ 140, K+ 3.8, Cl- 100, HCO3- 15
E. Na+ 130, K+ 5.8, Cl- 110, HCO3- 20
You did not answer this question.
Explanations:
A. Key teaching point #1: When you see a 3-6 week old infant with projectile vomiting, and an olive-like mass on physical exam, think pyloric stenosis! Key teaching point #2: Losing HCl in emesis
leads to a hypochloremic, hypokalemic metabolic alkalosis. This vignette describes a classic presentation of pyloric stenosis, a commonly-tested disorder for which the associated electrolyte
abnormality is a hypochloremic, hypokalemic metabolic alkalosis (answer A). Even without recognizing that this is a case of pyloric stenosis, you should be able to think through the question and
arrive at the correct answer. Think about what is going on with this patient. Repetitive vomiting of acidic gastric juices causes the loss of HCl – thus, the patient’s Cl- should be low. Since you’re
losing H+, there will also be a metabolic alkalosis, so the HCO3- will be elevated as well. Finally, in order to maintain pH balance, the kidneys avidly reabsorb H+, but they can only do this at the
expense of K+, resulting in hypokalemia. (Review Dr. Barrett’s diagrams of the principal and intercalated cells of the cortical collecting duct from her second year “Diuretics” lecture to remind
yourself of how this happens physiologically. http://www.med-ed.virginia.edu/courseSites/subjects.cfm?CID=1) Thinking about things this way, you’re looking for the answer that shows a
decrease in Cl- and K+, and an increase in HCO3- (answer A). As previously mentioned, the question stem describes a truly classic case of pyloric stenosis, which is important to recognize. Key
features include: 1) palpable abdominal mass – often described as an “olive” (Sometimes, the olive is only palpable after feedings, so doing a test feeding in clinic can confirm the diagnosis.); 2)
projectile vomiting; 3) vomiting immediately after feeding, then demanding to be refed - “hungry vomiters”; 4) presentation at age 3-6 weeks. The initial test of choice when the diagnosis is
unclear is abdominal ultrasound, which will reveal the hypertrophied pylorus. (Barium studies may also be used, but these have the undesirable side effect of exposing an infant to radiation.) The
treatment of pyloric stenosis is, of course, surgical – the patient needs a pyloromyotomy. Answer B represents essentially normal lab values, which this child would not be expected to
demonstrate given his dehydration and one week history of vomiting. The primary abnormality in answer C is hypernatremia. This situation results when a patient has hypotonic fluid loss, or
loses more water than they do sodium – as can happen in patients with dehydration with inadequate free water intake. It is important to realize that this patient is not losing hypotonic fluids,
however – he is losing large amounts of electrolytes with each episode of vomiting. The primary abnormality in Answer D is a low bicarbonate – which, in this situation, represents an anion gap
metabolic acidosis. Remember that Anion gap = sodium – chloride – bicarbonate = 12 +/- 4 The anion gap in this question stem would be 140 – 100 – 16 = 24, which is elevated. Possible
etiologies of an anion gap metabolic acidosis include the things on the MUDPILES mnemonic – none of which would apply to this patient. For an eMedicine article on metabolic acidosis
(including the MUDPILES mnemonic) check out: http://www.emedicine.com/ped/topic15.htm Answer E represents a patient with hyponatremia and hyperkalemia. This situation could arise in
adrenal insufficiency due to insufficient aldosterone.
B. Answer B represents essentially normal lab values, which this child would not be expected to demonstrate given his dehydration and one week history of vomiting.
C. The primary abnormality in answer C is hypernatremia. This situation results when a patient has hypotonic fluid loss, or loses more water than they do sodium – as can happen in patients with
dehydration with inadequate free water intake. It is important to realize that this patient is not losing hypotonic fluids, however – he is losing large amounts of electrolytes with each episode of
vomiting.
D. The primary abnormality in Answer D is a low bicarbonate – which, in this situation, represents an anion gap metabolic acidosis. Remember that Anion gap = sodium – chloride – bicarbonate =
12 +/- 4 The anion gap in this question stem would be 140 – 100 – 16 = 24, which is elevated. Possible etiologies of an anion gap metabolic acidosis include the things on the MUDPILES
mnemonic – none of which would apply to this patient. For an eMedicine article on metabolic acidosis (including the MUDPILES mnemonic) check out: http://www.emedicine.com/ped/topic15.htm
E. Answer E represents a patient with hyponatremia and hyperkalemia. This situation could arise in adrenal insufficiency due to insufficient aldosterone.
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Question # 4
Select the single best answer to the numbered question.
A 30 year old female presents to her physician with a breast mass. She first noted a small “lump” in her left breast while showering about six weeks ago. She has noted no change
in the size of the mass since that time, and she denies pain or nipple discharge. Family history is significant for a paternal grandmother who had breast cancer at age 79. Physical
examination reveals a soft, round, mobile 1cm mass in the lower outer quadrant of the left breast. No skin changes are noted. What is the most appropriate next step in the
management of this patient?
A. Mammography
B. Refer the patient for radical mastectomy
C. Begin levonorgestrel/etinyl estradiol
D. Genetic testing for BRCA1 and BRCA2
E. Ultrasound of breast mass
You did not answer this question.
Explanations:
A. Mammograms are not the best diagnostic study in a woman under 35 years old due to the density of breast tissue.
B. Answer B might be an appropriate treatment for some breast cancers. But to make a diagnosis of cancer requires tissue, so referral for mastectomy would certainly not be appropriate at this
time.
C. Many oral contraceptive pills (OCPs) contain combinations of levonorgestrel and ethinyl estradiol (answer C). There are some non-contraceptive indications for prescribing OCPs, such as
dysmenorrhea or endometriosis, and some practicioners do prescribe OCPs to help reduce the pain caused by hormonal fluctuations of benign breast cysts. This patient does not complain of
pain, however, and more importantly, you do not yet know what her breast mass is. While not all breast masses are pathological, they all demand an explanation. Since this patient is less than
35, she needs ultrasound.
D. Genetic testing for BRCA1 and BRCA2 (answer D) might be an appropriate step for an asymptomatic woman with a strong family history of breast cancer, or to evaluate ovarian cancer risk in a
patient with proven breast cancer. There are two reasons why this response is incorrect for this question, however. First, this patient’s family history of breast cancer is not terribly impressive.
Breast cancer is so common that 12% of all women will have a positive family history. To identify patients at risk for BRCA1 and BRCA2 mutations, look for patients with multiple first-degree
relatives (mothers, daughters, or sisters) who had breast or ovarian cancer at young ages (less than 40-50). In general, the USMLE tests the most classic presentation of any disease – for the
correct answer to be BRCA1/BRCA2 testing, the question stem would have to give you more than just one relative who had breast cancer at age 79. Second, and more important, even if this
patient had a family history that was suggestive for a BRCA1 or BRCA2 mutation, her problem right now is a breast mass that needs to be evaluated with imaging and potentially a biopsy.
Genetic testing might help you assess the patient’s lifetime breast cancer risk, but it will not help you determine if this particular breast mass is something bad or not.
E. Key teaching point: Mammogram is the preferred imaging study for women over 35, while women younger than 35 should get ultrasound to evaluate a breast mass. In women younger than 35,
the breast tissue is often too dense to evaluate mammographically, and the incidence of breast cancer younger women is still very low. Studies have shown that routine mammography is not
cost-effective nor clinically beneficial for younger women unless there is a high suspicion of cancer by clinical examination. The clinical characteristics of this mass are non-suspicious for
malignancy, though. Features commonly associated with malignancy include hard, irregularly-shaped, immobile masses >2cm in size. Since this patient’s mass is soft, small, rounded, and
mobile, it is likely to be a benign fibroadenoma. Thus, the patient should receive ultrasound, and the correct answer is E. If the patient were over 35, she should get a diagnostic mammogram
(answer A). Questions about the workup of a breast mass are common on the USMLE, so it is worth thinking about how the workup would proceed in this patient. If ultrasound were obtained and
the mass is found to be cystic in nature, it is very unlikely to be malignant, and no further evaluation is necessary (although the cyst may be aspirated if it is causing the patient pain). If it is solid,
however, tissue will be required to make a definitive diagnosis, and the patient should receive a biopsy. Since breast tissue may undergo changes related to the menstrual cycle, many clinicians
will simply ask a young patient with a breast mass to return 3-10 days following her next menstrual cycle to re-evaluate the lump. Answer B might be an appropriate treatment for some breast
cancers. But to make a diagnosis of cancer requires tissue, so referral for mastectomy would certainly not be appropriate at this time. Many oral contraceptive pills (OCPs) contain combinations
of levonorgestrel and ethinyl estradiol (answer C). There are some non-contraceptive indications for prescribing OCPs, such as dysmenorrhea or endometriosis, and some practicioners do
prescribe OCPs to help reduce the pain caused by hormonal fluctuations of benign breast cysts. This patient does not complain of pain, however, and more importantly, you do not yet know what
her breast mass is. While not all breast masses are pathological, they all demand an explanation. Since this patient is less than 35, she needs ultrasound. Genetic testing for BRCA1 and BRCA2
(answer D) might be an appropriate step for an asymptomatic woman with a strong family history of breast cancer, or to evaluate ovarian cancer risk in a patient with proven breast cancer. There
are two reasons why this response is incorrect for this question, however. First, this patient’s family history of breast cancer is not terribly impressive. Breast cancer is so common that 12% of all
women will have a positive family history. To identify patients at risk for BRCA1 and BRCA2 mutations, look for patients with multiple first-degree relatives (mothers, daughters, or sisters) who
had breast or ovarian cancer at young ages (less than 40-50). In general, the USMLE tests the most classic presentation of any disease – for the correct answer to be BRCA1/BRCA2 testing, the
question stem would have to give you more than just one relative who had breast cancer at age 79. Second, and more important, even if this patient had a family history that was suggestive for a
BRCA1 or BRCA2 mutation, her problem right now is a breast mass that needs to be evaluated with imaging and potentially a biopsy. Genetic testing might help you assess the patient’s lifetime
breast cancer risk, but it will not help you determine if this particular breast mass is something bad or not.
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Question # 5
Select the single best answer to the numbered question.
An otherwise healthy 8 year old girl presents with two weeks of perianal pruritis. She has two younger brothers, one of whom has had similar complaints for the past few days.
Physical exam reveals perianal erythema with mild excoriations. The “scotch tape test” reveals several bean-shaped white eggs. What is the most likely diagnosis in this patient?
A. Trichuriasis
B. Enterobiasis
C. Child abuse
D. Fecal soilage
E. Atopic dermatitis
You did not answer this question.
Explanations:
A. Whipworm or trichuriasis (choice A) is a common intestinal helminthic infection worldwide, with the highest prevalence in tropical regions. Hosts are usually asymptomatic, though the disease can
, A. Whipworm or trichuriasis (choice A) is a common intestinal helminthic infection worldwide, with the highest prevalence in tropical regions. Hosts are usually asymptomatic, though the disease can
cause loose stools that contain mucus or blood, resulting in a secondary anemia. Trichuriasis is also classically associated with rectal prolapse in a patient with a heavy parasite load. Heavy
loads can affect a child’s growth and cognition. Diagnosis is made by stool examination for eggs, which are barrel shaped with a hyaline plug at each end.
B. This is a classic case of enterobiasis (answer B) or “pinworm.” The most common presenting symptom is intense anal itching or pruritus ani. Other symptoms (such as abdominal pain/fullness or
nausea and vomiting) may occur if the worm burden is high. Girls may also present with a vulvovaginitis or urinary tract infection if the worms migrate. Eosinophilic enterocolitis and appendicitis
are rarer complications. Some teaching points: 1) The first line treatment of enterobiasis is either mebendazole or albendazole - one dose is usually sufficient, but a second dose 1-2 weeks later
can help prevent reinfection. Pyrantel pamoate is second line because of its side effects (nausea, vomiting, abdominal cramping, neurotoxicity, and elevated LFTs). However, pyrantel pamoate is
first line if the patient is pregnant, since mebendazole and albendazole are teratogenic. 2) Enterobiasis is spready by a fecal-oral route and usually presents in kids ages 5-10 years old. It is very
uncommon in children less than 2 years old. 3) The “scotch tape” test is the best way to confirm the diagnosis. It involves covering a wooden stick with scotch tape with the sticky side facing
outward, and then pressing the tape against the perianal skin. Bean-shaped eggs stick to the tape which can then be visualized under a microscope. Sometimes whole adult worms can be found
perianally - they are white, pin-shaped and can be up to 13 mm long. 4) Treatment should include simultaneous treatment of all household members to prevent reinfection. Bedding and clothing
should be washed, fingernails should be clipped (since this is the most common place for eggs to hide out), and hygienic measures increased (handwashing and bathing). Whipworm or
trichuriasis (choice A) is a common intestinal helminthic infection worldwide, with the highest prevalence in tropical regions. Hosts are usually asymptomatic, though the disease can cause loose
stools that contain mucus or blood, resulting in a secondary anemia. Trichuriasis is also classically associated with rectal prolapse in a patient with a heavy parasite load. Heavy loads can affect
a child’s growth and cognition. Diagnosis is made by stool examination for eggs, which are barrel shaped with a hyaline plug at each end. Child abuse (choice C) is not the best answer, though it
isn’t unreasonable to have this on your differential when children present with genital or anal complaints. In this case, we have a clear, identifiable cause of the perianal itching. Fecal soilage
(choice D) is part of the differential of anal pruritis and can be due to any cause of diarrhea or loose stools. Some patients have an abnormality with internal anal sphincter relaxation. When anal
itching is otherwise unexplained, this diagnosis should be entertained. Eczema or atopic dermatitis (choice E) is certainly part of the differential diagnosis of anal pruritis, though just the history
does suggest an infectious cause. This familial allergic reaction is often associated with asthma and allergic rhinitis. The rash of eczema is intensely pruritic, and usually appears as erythematous
patches with scaling. In children, eczema usually occurs on the face, scalp, extremities, diaper area and trunk, and usually presents by age 7.
C. Child abuse (choice C) is not the best answer, though it isn’t unreasonable to have this on your differential when children present with genital or anal complaints. In this case, we have a clear,
identifiable cause of the perianal itching.
D. Fecal soilage (choice D) is part of the differential of anal pruritis and can be due to any cause of diarrhea or loose stools. Some patients have an abnormality with internal anal sphincter
relaxation. When anal itching is otherwise unexplained, this diagnosis should be entertained.
E. Eczema or atopic dermatitis (choice E) is certainly part of the differential diagnosis of anal pruritis, though just the history does suggest an infectious cause. This familial allergic reaction is often
associated with asthma and allergic rhinitis. The rash of eczema is intensely pruritic, and usually appears as erythematous patches with scaling. In children, eczema usually occurs on the face,
scalp, extremities, diaper area and trunk, and usually presents by age 7.
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Question # 6
Select the single best answer to the numbered question.
A 66 year old male presents to the emergency department with chest pain. The pain began two hours ago as the patient was watching television. The pain is described as
"squeezing" and is located primarily substernally with radiation to the jaw. Past medical history includes diabetes mellitus, hypertension, hyperlipidemia, and a 50 pack/year smoking
habit. On physical exam, the patient appears anxious and diaphoretic. The patient is given supplemental oxygen by nasal cannula, and aspirin, morphine, and nitroglycerin are
administered. EKG obtained on presentation to the ED is shown. Of the following, which is the most appropriate study to obtain next?
, A. Aortogram
B. Troponin I
C. Stress echo
D. Exercise stress test
E. CT angiogram of chest
You did not answer this question.
Explanations:
A. An aortogram (answer A) used to be the gold standard for the diagnosis of an aortic aneurysm. Now, less-invasive imaging modalities such as CT, MRI, and echo have largely supplanted
aortograms for the diagnosis of aortic dissection. In any case, while aortic dissection ought to be considered in patients with chest pain, this patient’s history is strongly suggestive of ACS, and
this should be investigated first.
B. Key teaching point: To evaluate acute coronary syndrome, you need both an EKG and serial troponins. The patient presents with symptoms highly suggestive of acute coronary syndrome (ACS).
Collectively, ACS consists of three ischemic cardiac disorders: ST-elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI), and unstable angina. Distinguishing
between these entities is important, as both the therapy and the prognosis depends on the diagnosis. The first thing to do when sorting out ACS is to check an EKG – the presence of ST
segment elevation (>1 mm in two or more anatomically contiguous leads) confirms the diagnosis of a STEMI. STEMI carries the worst prognosis of any of any of the acute coronary syndromes,
so finding “tombstones” of ST elevation on EKG is a clear indication for immediate reperfusion therapy, either with thrombolytics or percutaneous interventions in the cath lab. This patient’s EKG
shows little more than normal sinus rhythm. The lack of ST elevation means that the diagnosis of STEMI is ruled out. (As a sidenote: If you answered this question incorrectly because you
thought that there was miniscule ST elevation on this EKG, here is the teaching point for you. When you are looking at an image on the USMLE or shelf exam, whether that image is a CT scan, a
radiograph, or an EKG, expect any abnormalities to be STRIKING. The testmakers do not expect you to be a radiologist or to hold your EKG calipers up to the computer monitor. You need to use
the information from the question stem to know whether you’re looking for a fracture, a head bleed, atrial fibrillation, etc., but so long as you know what to look for, the finding in the image will
either be obvious - or it will be absent.) So now that the patient has a relatively normal EKG, how do we distinguish between the other acute coronary syndromes - NSTEMI and unstable angina?
You need a biomarker to tell you if the patient's cardiac tissue has infarcted, and although you could use CK-MB or LDH, the most sensitive and specific test is cardiac troponins (answer B). If
this patient's troponin I were elevated, it would indicate ischemic necrosis of the myocardium - therefore, the patient is having an MI, even if we don't see it on EKG. The appropriate diagnosis
would thus be NSTEMI. (Pathologically, to have ST segment elevation on EKG requires a full-thickness infarction of the myocardium. If an infarction does not penetrate the entire thickness of the
heart wall, the heart’s electrical conduction is relatively undisturbed and there will not be diagnostic findings on EKG.) The management of NSTEMI is still evolving and remains somewhat
controversial. Reperfusion with primary percutaneous interventions in the cath lab is beneficial for high-risk patients, but thrombolytic therapy carries greater risks and is reserved for those
patients with persisting ST elevations. Many patients with NSTEMI can also be managed medically with antiplatelet therapy and beta blockers. If the patient's troponin I were not elevated, then
the patient has not yet infarcted his myocardium. The diagnosis would therefore be unstable angina, which requires intensive medical management to prevent MI. The patient should be started
on some regimen of heparin, beta blockers, and antiplatelet therapy. The patient should also receive EKG monitoring and serial troponins to ensure that his unstable angina does not eventually
cause infarction. An aortogram (answer A) used to be the gold standard for the diagnosis of an aortic aneurysm. Now, less-invasive imaging modalities such as CT, MRI, and echo have largely
supplanted aortograms for the diagnosis of aortic dissection. In any case, while aortic dissection ought to be considered in patients with chest pain, this patient’s history is strongly suggestive of
ACS, and this should be investigated first. A stress echocardiogram (answer C) or exercise stress test (answer D) might be good tests to risk stratify a medically stable, low-risk patient with
suspected coronary artery disease. This patient, however, requires further evaluation to rule out MI, and stressing the heart is a bad idea in a patient with probable ongoing ischemic pain.
Obtaining a CT pulmonary angiogram (answer E) would be a great test to rule out pulmonary embolism, which can be a cause of chest pain. Here, though, the patient’s history and cardiac risk
factors strongly suggest a cardiac etiology for his pain, so until that is ruled out, searching for a PE is inappropriate.
C. A stress echocardiogram (answer C) or exercise stress test (answer D) might be good tests to risk stratify a medically stable, low-risk patient with suspected coronary artery disease. This patient,
however, requires further evaluation to rule out MI, and stressing the heart is a bad idea in a patient with probable ongoing ischemic pain.
D. A stress echocardiogram (answer C) or exercise stress test (answer D) might be good tests to risk stratify a medically stable, low-risk patient with suspected coronary artery disease. This patient,
however, requires further evaluation to rule out MI, and stressing the heart is a bad idea in a patient with probable ongoing ischemic pain.
E. Obtaining a CT pulmonary angiogram (answer E) would be a great test to rule out pulmonary embolism, which can be a cause of chest pain. Here, though, the patient’s history and cardiac risk
factors strongly suggest a cardiac etiology for his pain, so until that is ruled out, searching for a PE is inappropriate.
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Question # 7
Select the single best answer to the numbered question.
A 73 year old male presents to his physician complaining of cough and fatigue. His cough began 6 months ago and has steadily worsened, and is now associated with occasional
expectoration of mucus streaked with bright red blood. Patient has also noted worsening dyspnea on exertion and a weight loss of 15 lbs. The patient has smoked a pack and a half
of cigarettes every day for the past 60 years. Past medical history is significant for bipolar disorder treated with lithium. Physical exam shows unilateral localized wheezing on the left
chest and clubbing of the distal extremities. Capillary refill is brisk. No skin tenting is observed. Chest X-ray is obtained, which shows a large mass at the left hilum. Labs show:
Glucose 130, Na+ 125, K+ 4.0, Cl- 91, HCO3- 25, BUN 15, Creatinine 1.0; Plasma osmolality 270 (Normal: 282-295 mOsm/kg); Urine osmolality 650 mOsm/kg (Normal: 50 - 1400
mOsm/kg). Which of the following is the most likely mechanism for this patient's hyponatremia?
A. Increased oral intake of hypotonic fluids
B. Decreased oral intake of solutes
C. Impaired secretion of ADH in the posterior pituitary
D. Ectopic overproduction of vasopressin
E. Resistance to ADH action on the cortical and medullary collecting tubules
You did not answer this question.
Explanations:
A. Increased free water intake (answer A) describes the situation seen in psychogenic polydipsia, a disorder in which patients - most commonly schizophrenics receiving antipsychotics - drink
excessive amounts of free water. The kidneys have an incredible capacity for regulating fluids and solutes. Normal patients can excrete more than 10-15 L of urine per day, so for a patient with a
dietary solute intake to become hyponatremic, they would have to have a very impressive water intake!
B. Decreased solute intake (answer B) is the mechanism for “beer potomania,” in which patients drink excessive amounts of beer without taking in enough food to provide adequate solutes. The
minimum urine osmolality is 60mOsm/kg, so there is a certain amount of obligatory solute lost in the urine every day. If a patient is only drinking beer (and massive quantities of it) and not taking
in any solutes, he can deplete his solute reserves over time just through this obligatory solute loss.
C. Answers C and E describe the abnormalities present in diabetes insipidus (DI). DI is a frequently-tested topic on the USMLE, but it is most likely to present with HYPERnatremia, not
HYPOnatremia. There are two types of DI: central and nephrogenic. In central DI (answer C), there is not enough ADH produced by the pituitary, while in nephrogenic DI (answer E), there is end-
organ resistance to ADH action. In either case, the kidney is no longer able to reabsorb H2O from the urine, leading to free water losses and copious polyuria. Since the body is losing more free
water than solute, patients typically become hypernatremic. In children, nephrogenic DI is almost always inherited, while in adults it is commonly caused by drugs - most notably lithium. Central
DI is most commonly caused by surgical trauma to the hypothalamus or pituitary, such as might occur with a trans-sphenoidal removal of a pituitary adenoma.
D. Key teaching point: When you see euvolemic hyponatremia (especially on the USMLE), think SIADH! The constellation of findings in this patient, including euvolemic hyponatremia, hypotonicity
(plasma osmolality <280 mOsms), inappropriately concentrated urine, and normal renal function are diagnostic for the syndrome of inappropriate ADH secretion (SIADH). SIADH has a number of
causes. The most common include: 1) Cancer - ectopic production of ADH by small cell lung cancers or pancreatic malignancies; 2) CNS disturbances - traumatic injuries, strokes, infections, and
hemorrhages can all cause increased ADH production; 3) Drugs - most commonly caused by antipsychotic medications or chemotherapeutics, but the old (and seldom used) insulin
secretagogue chlorpropamide is a commonly-tested causative agent. This question stem is loaded with findings consistent with primary lung carcinoma in general and small cell carcinoma in
particular: a older patient with an extensive smoking history; insidious onset of cough, fatigue, and weight loss; localized wheezing and clubbing of the nails; and a chest x-ray showing a central
mass. Therefore, it is overwhelmingly likely that overproduction of ADH – also known as vasopressin - by the patient's lung tumor is causing his hyponatremia (answer D). Both answers A and B
are plausible explanations for hyponatremia in general. However, as mentioned above, this patient's history and physical exam strongly suggest lung cancer, which is associated with SIADH.
Additionally, either of these situations would be associated with a maximally diluted urine osmolality, while the patient in the question stem has inappropriately concentrated urine. Increased free
water intake (answer A) describes the situation seen in psychogenic polydipsia, a disorder in which patients - most commonly schizophrenics receiving antipsychotics - drink excessive amounts
of free water. The kidneys have an incredible capacity for regulating fluids and solutes. Normal patients can excrete more than 10-15 L of urine per day, so for a patient with a dietary solute intake
to become hyponatremic, they would have to have a very impressive water intake! Decreased solute intake (answer B) is the mechanism for “beer potomania,” in which patients drink excessive
amounts of beer without taking in enough food to provide adequate solutes. The minimum urine osmolality is 60mOsm/kg, so there is a certain amount of obligatory solute lost in the urine every
day. If a patient is only drinking beer (and massive quantities of it) and not taking in any solutes, he can deplete his solute reserves over time just through this obligatory solute loss. Answers C
and E describe the abnormalities present in diabetes insipidus (DI). DI is a frequently-tested topic on the USMLE, but it is most likely to present with HYPERnatremia, not HYPOnatremia. There
are two types of DI: central and nephrogenic. In central DI (answer C), there is not enough ADH produced by the pituitary, while in nephrogenic DI (answer E), there is end-organ resistance to
ADH action. In either case, the kidney is no longer able to reabsorb H2O from the urine, leading to free water losses and copious polyuria. Since the body is losing more free water than solute,
patients typically become hypernatremic. In children, nephrogenic DI is almost always inherited, while in adults it is commonly caused by drugs - most notably lithium. Central DI is most
commonly caused by surgical trauma to the hypothalamus or pituitary, such as might occur with a trans-sphenoidal removal of a pituitary adenoma.
E. Answers C and E describe the abnormalities present in diabetes insipidus (DI). DI is a frequently-tested topic on the USMLE, but it is most likely to present with HYPERnatremia, not
HYPOnatremia. There are two types of DI: central and nephrogenic. In central DI (answer C), there is not enough ADH produced by the pituitary, while in nephrogenic DI (answer E), there is end-
organ resistance to ADH action. In either case, the kidney is no longer able to reabsorb H2O from the urine, leading to free water losses and copious polyuria. Since the body is losing more free
water than solute, patients typically become hypernatremic. In children, nephrogenic DI is almost always inherited, while in adults it is commonly caused by drugs - most notably lithium. Central
DI is most commonly caused by surgical trauma to the hypothalamus or pituitary, such as might occur with a trans-sphenoidal removal of a pituitary adenoma.
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Your Score: 1 % (124 unanswered questions) Exit
Question # 1
Select the single best answer to the numbered question.
A 50 year old female with a ten year history of type II diabetes presents for regularly-scheduled follow up. She has no complaints, and just visited her ophthalmologist last week.
Current medications include glyburide, metformin, and simvastatin. On physical exam, vital signs are virtually unchanged from previous visits, with temperature 37.1 C (99 F), HR
80, BP 140/83, RR 15, and O2 Sat 98% on room air. Neurological examination reveals diminished sensation to light touch and pinprick in a stocking distribution on the lower
extremities bilaterally. Remainder of physical exam is benign. Laboratory evaluation reveals: Na+ 136, K+ 3.9 Cl- 104, HCO3- 25, BUN 15, Cr 1.0, Glucose 150; hemoglobin A1c:
7.1%; Urinalysis: negative for ketones, glucose, bilirubin, leukocyte esterase, or blood; moderate protein; Lipid profile: Total cholesterol 146, HDL 46, LDL 100. At this time, which of
the following would be the most appropriate intervention?
A. Increase simvastatin
B. Increase glyburide
C. Increase metformin
D. Add hydrochlorothiazide
E. Add lisinopril
You answered: E
Explanations:
A. The patient’s lipid profile is technically at her target LDL – thus, she does not need an increase in her statin (answer A). Under the current ATP III guidelines, patients with diabetes are considered to have known coronary
heart disease, and therefore have a target LDL of less than 100. To review the ATP III lipid guidelines at a glance, check out http://www.nhlbi.nih.gov/guidelines/cholesterol/atglance.pdf HOWEVER, please note that
although the official guideline is still LDL <100, that figure is likely to change in the future, because new evidence has come out showing that lower LDLs (<70) are better... so in the near future, this question may have two
correct answers!
B. Either increasing glyburide (answer B) or increasing metformin (answer C) would be helpful for reducing the patient’s blood sugar and better controlling her diabetes. However, her most recent Hgb A1c was not that bad –
remember that the goal for diabetic patients is less than 7.0%. For more on Hgb A1c, including how to correlate the test result with the patient’s average blood glucose, check out Diabetes Care 2002;25:275-8 or
http://www.metrika.com/3medical/hemoglobin-m.html.
C. Either increasing glyburide (answer B) or increasing metformin (answer C) would be helpful for reducing the patient’s blood sugar and better controlling her diabetes. However, her most recent Hgb A1c was not that bad –
remember that the goal for diabetic patients is less than 7.0%. For more on Hgb A1c, including how to correlate the test result with the patient’s average blood glucose, check out Diabetes Care 2002;25:275-8 or
http://www.metrika.com/3medical/hemoglobin-m.html.
D. Adding hydrochlorothiazide (answer D) could improve her hypertension, and would be a reasonable first-line antihypertensive in a patient without diabetes. It is worth noting that this patient IS hypertensive – all diabetics
should have a systolic blood pressure of less than 130. Still, diabetic patients have a compelling reason to begin antihypertensive therapy with ACE inhibitors or ARBs, however, due to the reno-protective effects of these
drugs.
E. Key teaching point: All diabetics should be on an ACE inhibitor or ARB for cardiovascular and renal protection. This is a dense question stem, but the important things to note are that this is a patient with type II diabetes
who also has proteinuria and elevated blood pressure. Since her medication list does not include any mention of an ACE inhibitor or ARB, beginning one at this time would be the appropriate next step in management
(answer E). As it turns out, microalbuminuria is a risk factor for both cardiovascular disease and progression of renal disease to ESRD and dialysis – and this patient already has macroalbuminuria, since dipsticks are not
sensitive enough to pick up small amounts of protein! ACE inhibitors and ARBs have been shown to reduce these outcomes – even in normotensive diabetics. All diabetics, therefore, should be on an ACE inhibitor or
ARB. Since this patient is hypertensive as well, she has all the more reason to begin a medication such as lisinopril. (It is, however, also important to note that the diagnosis of hypertension should not be made on the
basis of a single blood pressure measurement in a physician’s office. In this case, the question stem mentions that her vital signs have been similar to those recorded in the past, so making a diagnosis of hypertension is
more acceptable. Additionally, diabetics have a target blood pressure of systolic less than 130 mm Hg, a more stringent guideline than for non-diabetic patients.) As an additional teaching point, every health maintenance
visit with a diabetic patient should focus on the “Diabetic Five” – these five things, in this order: 1) Smoking cessation 2) Blood pressure control 3) Lipid control 4) Aspirin/metformin 5) Glucose control Adding
hydrochlorothiazide (answer D) could improve her hypertension, and would be a reasonable first-line antihypertensive in a patient without diabetes. It is worth noting that this patient IS hypertensive – all diabetics should
have a systolic blood pressure of less than 130. Still, diabetic patients have a compelling reason to begin antihypertensive therapy with ACE inhibitors or ARBs, however, due to the reno-protective effects of these drugs
mentioned above. Either increasing glyburide (answer B) or increasing metformin (answer C) would be helpful for reducing the patient’s blood sugar and better controlling her diabetes. However, her most recent Hgb A1c
was not that bad – remember that the goal for diabetic patients is less than 7.0%. For more on Hgb A1c, including how to correlate the test result with the patient’s average blood glucose, check out Diabetes Care
2002;25:275-8 or http://www.metrika.com/3medical/hemoglobin-m.html. Similarly, the patient’s lipid profile is at her target LDL – thus, she does not need an increase in her statin (answer A). Under the ATP III guidelines,
patients with diabetes are considered to have known coronary heart disease, and therefore have a target LDL of less than 100. To review the ATP III lipid guidelines at a glance, check out
http://www.nhlbi.nih.gov/guidelines/cholesterol/atglance.pdf For an overview of diabetic nephropathy, try Ritz E., Orth S. R. Primary Care: Nephropathy in Patients with Diabetes Mellitus. N Engl J Med 1999; 341:1127-
1133, Oct 7, 1999. http://content.nejm.org/cgi/reprint/341/15/1127.pdf?
hits=20&where=fulltext&andorexactfulltext=and&searchterm=diabetes&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&excludeflag=TWEEK_element&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
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Question # 2
Select the single best answer to the numbered question.
A 55 year old female comes to the emergency department complaining of a headache for the past six hours. Her headache began abruptly after she finished eating breakfast, and
quickly increased to 8/10 throbbing pain located mainly over her right temple. The pain has been associated with mild nausea but no vomiting. She denies chronic or recurrent
headaches, but did have one headache similar to this one two weeks ago, which resolved after taking ibuprofen and lying in a quiet, dark room. She has smoked one pack of
cigarettes daily for 38 years. On physical exam, the patient has temperature of 37.0 C (98.6 F), pulse of 99, and BP 147/95. Neurological examination is nonfocal, but mild
photophobia and nuchal rigidity are noted. Fundoscopic examination reveals no papilledema. Skin exam shows no lesions. CT of the head, obtained without contrast, reveals no
abnormalities. What is the most appropriate next step in the management of this patient?
A. Obtain head CT with contrast
B. Lumbar puncture
C. Administer i.m. sumatriptan
D. Administer oral ibuprofen
E. Administer i.v. ceftriaxone
You did not answer this question.
Explanations:
A. CT with contrast (answer A) might help you identify a space-occupying lesion, such as a tumor - which can certainly be a cause of headache. However, such lesions are not likely to cause a
sudden onset headache such as the one described in the question stem. Remember that CT without contrast is the best study to identify an acute head bleed, whether you’re looking for a stroke,
a hematoma, or a hemorrhage.
B. No explanation provided.
C. Sumatriptan injection (answer C) would be a fine choice if the patient were having a migraine. Migraine headache pain does lateralize in 60-70% of patients, may be associated with photophobia
or nausea, and be relieved by NSAIDs or lying in a dark room. However, most patients with migraine have their first symptoms in adolescence or early adulthood. A new-onset migraine in a
patient 55 years old would be very unusual. (It is important to recognize that the patient’s headache two weeks ago was likely a “sentinel bleed” from an aneurysm.) Additionally, migraines are
frequently associated with sensory “auras” such as visual scotomata or paresthesias.
D. Ibuprofen (answer D) is a reasonable first-line treatment for a patient with a tension headache. These headaches are typically bilateral, and would seldom become intense enough to necessitate
a visit to the ER.
E. Ceftriaxone (answer E) is the most commonly used empiric antibiotic for adults with suspected bacterial meningitis since it penetrates the CSF and covers the most likely pathogens in this age
group: S. pneumoniae (60%) and N. meningitides (20%). This patient is afebrile, however, and her stiff neck and photophobia are simply signs of meningeal irritation – which in this case is
caused by SAH, not a bacterial infection. Meningitis may cause headache, but not as suddenly as the headache described in the question. Even if this patient was suspected to have meningitis,
you would likely want to obtain an LP before giving antibiotics so that you don’t sterilize the cultures! After obtaining an LP, antibiotic therapy with ceftriaxone (or cefotaxime) and vancomycin
could be started. (The latter is used to cover the possibility of drug-resistant S. pneumoniae while you await results of the CSF culture.)
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Question # 3
Select the single best answer to the numbered question.
A four week old male infant is brought by his mother to the physician following one week of emesis. The patient’s mother states that the patient has been vomiting non-bilious
material immediately after each feeding, but then becomes fussy and demands to be fed again. She denies ever seeing any blood in the emesis. Over the past two or three days,
the infant’s vomiting has become increasingly sudden and forceful. The child is irritable, with few tears. The oropharynx is dry, the infant’s fontanelles appear sunken, and moderate
skin tenting is noted. Capillary refill is approximately 2 seconds. On abdominal exam, visible peristaltic waves are observed, and a 1cm firm mass is palpated in the right upper
quadrant. What is the most likely laboratory finding?
A. Na+ 130, K+ 2.9, Cl- 89, HCO3- 35
B. Na+ 138, K+ 3.8, Cl- 100, HCO3- 26
, B. Na+ 138, K+ 3.8, Cl- 100, HCO3- 26
C. Na+ 150, K+ 4.0, Cl- 100, HCO3- 24
D. Na+ 140, K+ 3.8, Cl- 100, HCO3- 15
E. Na+ 130, K+ 5.8, Cl- 110, HCO3- 20
You did not answer this question.
Explanations:
A. Key teaching point #1: When you see a 3-6 week old infant with projectile vomiting, and an olive-like mass on physical exam, think pyloric stenosis! Key teaching point #2: Losing HCl in emesis
leads to a hypochloremic, hypokalemic metabolic alkalosis. This vignette describes a classic presentation of pyloric stenosis, a commonly-tested disorder for which the associated electrolyte
abnormality is a hypochloremic, hypokalemic metabolic alkalosis (answer A). Even without recognizing that this is a case of pyloric stenosis, you should be able to think through the question and
arrive at the correct answer. Think about what is going on with this patient. Repetitive vomiting of acidic gastric juices causes the loss of HCl – thus, the patient’s Cl- should be low. Since you’re
losing H+, there will also be a metabolic alkalosis, so the HCO3- will be elevated as well. Finally, in order to maintain pH balance, the kidneys avidly reabsorb H+, but they can only do this at the
expense of K+, resulting in hypokalemia. (Review Dr. Barrett’s diagrams of the principal and intercalated cells of the cortical collecting duct from her second year “Diuretics” lecture to remind
yourself of how this happens physiologically. http://www.med-ed.virginia.edu/courseSites/subjects.cfm?CID=1) Thinking about things this way, you’re looking for the answer that shows a
decrease in Cl- and K+, and an increase in HCO3- (answer A). As previously mentioned, the question stem describes a truly classic case of pyloric stenosis, which is important to recognize. Key
features include: 1) palpable abdominal mass – often described as an “olive” (Sometimes, the olive is only palpable after feedings, so doing a test feeding in clinic can confirm the diagnosis.); 2)
projectile vomiting; 3) vomiting immediately after feeding, then demanding to be refed - “hungry vomiters”; 4) presentation at age 3-6 weeks. The initial test of choice when the diagnosis is
unclear is abdominal ultrasound, which will reveal the hypertrophied pylorus. (Barium studies may also be used, but these have the undesirable side effect of exposing an infant to radiation.) The
treatment of pyloric stenosis is, of course, surgical – the patient needs a pyloromyotomy. Answer B represents essentially normal lab values, which this child would not be expected to
demonstrate given his dehydration and one week history of vomiting. The primary abnormality in answer C is hypernatremia. This situation results when a patient has hypotonic fluid loss, or
loses more water than they do sodium – as can happen in patients with dehydration with inadequate free water intake. It is important to realize that this patient is not losing hypotonic fluids,
however – he is losing large amounts of electrolytes with each episode of vomiting. The primary abnormality in Answer D is a low bicarbonate – which, in this situation, represents an anion gap
metabolic acidosis. Remember that Anion gap = sodium – chloride – bicarbonate = 12 +/- 4 The anion gap in this question stem would be 140 – 100 – 16 = 24, which is elevated. Possible
etiologies of an anion gap metabolic acidosis include the things on the MUDPILES mnemonic – none of which would apply to this patient. For an eMedicine article on metabolic acidosis
(including the MUDPILES mnemonic) check out: http://www.emedicine.com/ped/topic15.htm Answer E represents a patient with hyponatremia and hyperkalemia. This situation could arise in
adrenal insufficiency due to insufficient aldosterone.
B. Answer B represents essentially normal lab values, which this child would not be expected to demonstrate given his dehydration and one week history of vomiting.
C. The primary abnormality in answer C is hypernatremia. This situation results when a patient has hypotonic fluid loss, or loses more water than they do sodium – as can happen in patients with
dehydration with inadequate free water intake. It is important to realize that this patient is not losing hypotonic fluids, however – he is losing large amounts of electrolytes with each episode of
vomiting.
D. The primary abnormality in Answer D is a low bicarbonate – which, in this situation, represents an anion gap metabolic acidosis. Remember that Anion gap = sodium – chloride – bicarbonate =
12 +/- 4 The anion gap in this question stem would be 140 – 100 – 16 = 24, which is elevated. Possible etiologies of an anion gap metabolic acidosis include the things on the MUDPILES
mnemonic – none of which would apply to this patient. For an eMedicine article on metabolic acidosis (including the MUDPILES mnemonic) check out: http://www.emedicine.com/ped/topic15.htm
E. Answer E represents a patient with hyponatremia and hyperkalemia. This situation could arise in adrenal insufficiency due to insufficient aldosterone.
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Question # 4
Select the single best answer to the numbered question.
A 30 year old female presents to her physician with a breast mass. She first noted a small “lump” in her left breast while showering about six weeks ago. She has noted no change
in the size of the mass since that time, and she denies pain or nipple discharge. Family history is significant for a paternal grandmother who had breast cancer at age 79. Physical
examination reveals a soft, round, mobile 1cm mass in the lower outer quadrant of the left breast. No skin changes are noted. What is the most appropriate next step in the
management of this patient?
A. Mammography
B. Refer the patient for radical mastectomy
C. Begin levonorgestrel/etinyl estradiol
D. Genetic testing for BRCA1 and BRCA2
E. Ultrasound of breast mass
You did not answer this question.
Explanations:
A. Mammograms are not the best diagnostic study in a woman under 35 years old due to the density of breast tissue.
B. Answer B might be an appropriate treatment for some breast cancers. But to make a diagnosis of cancer requires tissue, so referral for mastectomy would certainly not be appropriate at this
time.
C. Many oral contraceptive pills (OCPs) contain combinations of levonorgestrel and ethinyl estradiol (answer C). There are some non-contraceptive indications for prescribing OCPs, such as
dysmenorrhea or endometriosis, and some practicioners do prescribe OCPs to help reduce the pain caused by hormonal fluctuations of benign breast cysts. This patient does not complain of
pain, however, and more importantly, you do not yet know what her breast mass is. While not all breast masses are pathological, they all demand an explanation. Since this patient is less than
35, she needs ultrasound.
D. Genetic testing for BRCA1 and BRCA2 (answer D) might be an appropriate step for an asymptomatic woman with a strong family history of breast cancer, or to evaluate ovarian cancer risk in a
patient with proven breast cancer. There are two reasons why this response is incorrect for this question, however. First, this patient’s family history of breast cancer is not terribly impressive.
Breast cancer is so common that 12% of all women will have a positive family history. To identify patients at risk for BRCA1 and BRCA2 mutations, look for patients with multiple first-degree
relatives (mothers, daughters, or sisters) who had breast or ovarian cancer at young ages (less than 40-50). In general, the USMLE tests the most classic presentation of any disease – for the
correct answer to be BRCA1/BRCA2 testing, the question stem would have to give you more than just one relative who had breast cancer at age 79. Second, and more important, even if this
patient had a family history that was suggestive for a BRCA1 or BRCA2 mutation, her problem right now is a breast mass that needs to be evaluated with imaging and potentially a biopsy.
Genetic testing might help you assess the patient’s lifetime breast cancer risk, but it will not help you determine if this particular breast mass is something bad or not.
E. Key teaching point: Mammogram is the preferred imaging study for women over 35, while women younger than 35 should get ultrasound to evaluate a breast mass. In women younger than 35,
the breast tissue is often too dense to evaluate mammographically, and the incidence of breast cancer younger women is still very low. Studies have shown that routine mammography is not
cost-effective nor clinically beneficial for younger women unless there is a high suspicion of cancer by clinical examination. The clinical characteristics of this mass are non-suspicious for
malignancy, though. Features commonly associated with malignancy include hard, irregularly-shaped, immobile masses >2cm in size. Since this patient’s mass is soft, small, rounded, and
mobile, it is likely to be a benign fibroadenoma. Thus, the patient should receive ultrasound, and the correct answer is E. If the patient were over 35, she should get a diagnostic mammogram
(answer A). Questions about the workup of a breast mass are common on the USMLE, so it is worth thinking about how the workup would proceed in this patient. If ultrasound were obtained and
the mass is found to be cystic in nature, it is very unlikely to be malignant, and no further evaluation is necessary (although the cyst may be aspirated if it is causing the patient pain). If it is solid,
however, tissue will be required to make a definitive diagnosis, and the patient should receive a biopsy. Since breast tissue may undergo changes related to the menstrual cycle, many clinicians
will simply ask a young patient with a breast mass to return 3-10 days following her next menstrual cycle to re-evaluate the lump. Answer B might be an appropriate treatment for some breast
cancers. But to make a diagnosis of cancer requires tissue, so referral for mastectomy would certainly not be appropriate at this time. Many oral contraceptive pills (OCPs) contain combinations
of levonorgestrel and ethinyl estradiol (answer C). There are some non-contraceptive indications for prescribing OCPs, such as dysmenorrhea or endometriosis, and some practicioners do
prescribe OCPs to help reduce the pain caused by hormonal fluctuations of benign breast cysts. This patient does not complain of pain, however, and more importantly, you do not yet know what
her breast mass is. While not all breast masses are pathological, they all demand an explanation. Since this patient is less than 35, she needs ultrasound. Genetic testing for BRCA1 and BRCA2
(answer D) might be an appropriate step for an asymptomatic woman with a strong family history of breast cancer, or to evaluate ovarian cancer risk in a patient with proven breast cancer. There
are two reasons why this response is incorrect for this question, however. First, this patient’s family history of breast cancer is not terribly impressive. Breast cancer is so common that 12% of all
women will have a positive family history. To identify patients at risk for BRCA1 and BRCA2 mutations, look for patients with multiple first-degree relatives (mothers, daughters, or sisters) who
had breast or ovarian cancer at young ages (less than 40-50). In general, the USMLE tests the most classic presentation of any disease – for the correct answer to be BRCA1/BRCA2 testing, the
question stem would have to give you more than just one relative who had breast cancer at age 79. Second, and more important, even if this patient had a family history that was suggestive for a
BRCA1 or BRCA2 mutation, her problem right now is a breast mass that needs to be evaluated with imaging and potentially a biopsy. Genetic testing might help you assess the patient’s lifetime
breast cancer risk, but it will not help you determine if this particular breast mass is something bad or not.
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Question # 5
Select the single best answer to the numbered question.
An otherwise healthy 8 year old girl presents with two weeks of perianal pruritis. She has two younger brothers, one of whom has had similar complaints for the past few days.
Physical exam reveals perianal erythema with mild excoriations. The “scotch tape test” reveals several bean-shaped white eggs. What is the most likely diagnosis in this patient?
A. Trichuriasis
B. Enterobiasis
C. Child abuse
D. Fecal soilage
E. Atopic dermatitis
You did not answer this question.
Explanations:
A. Whipworm or trichuriasis (choice A) is a common intestinal helminthic infection worldwide, with the highest prevalence in tropical regions. Hosts are usually asymptomatic, though the disease can
, A. Whipworm or trichuriasis (choice A) is a common intestinal helminthic infection worldwide, with the highest prevalence in tropical regions. Hosts are usually asymptomatic, though the disease can
cause loose stools that contain mucus or blood, resulting in a secondary anemia. Trichuriasis is also classically associated with rectal prolapse in a patient with a heavy parasite load. Heavy
loads can affect a child’s growth and cognition. Diagnosis is made by stool examination for eggs, which are barrel shaped with a hyaline plug at each end.
B. This is a classic case of enterobiasis (answer B) or “pinworm.” The most common presenting symptom is intense anal itching or pruritus ani. Other symptoms (such as abdominal pain/fullness or
nausea and vomiting) may occur if the worm burden is high. Girls may also present with a vulvovaginitis or urinary tract infection if the worms migrate. Eosinophilic enterocolitis and appendicitis
are rarer complications. Some teaching points: 1) The first line treatment of enterobiasis is either mebendazole or albendazole - one dose is usually sufficient, but a second dose 1-2 weeks later
can help prevent reinfection. Pyrantel pamoate is second line because of its side effects (nausea, vomiting, abdominal cramping, neurotoxicity, and elevated LFTs). However, pyrantel pamoate is
first line if the patient is pregnant, since mebendazole and albendazole are teratogenic. 2) Enterobiasis is spready by a fecal-oral route and usually presents in kids ages 5-10 years old. It is very
uncommon in children less than 2 years old. 3) The “scotch tape” test is the best way to confirm the diagnosis. It involves covering a wooden stick with scotch tape with the sticky side facing
outward, and then pressing the tape against the perianal skin. Bean-shaped eggs stick to the tape which can then be visualized under a microscope. Sometimes whole adult worms can be found
perianally - they are white, pin-shaped and can be up to 13 mm long. 4) Treatment should include simultaneous treatment of all household members to prevent reinfection. Bedding and clothing
should be washed, fingernails should be clipped (since this is the most common place for eggs to hide out), and hygienic measures increased (handwashing and bathing). Whipworm or
trichuriasis (choice A) is a common intestinal helminthic infection worldwide, with the highest prevalence in tropical regions. Hosts are usually asymptomatic, though the disease can cause loose
stools that contain mucus or blood, resulting in a secondary anemia. Trichuriasis is also classically associated with rectal prolapse in a patient with a heavy parasite load. Heavy loads can affect
a child’s growth and cognition. Diagnosis is made by stool examination for eggs, which are barrel shaped with a hyaline plug at each end. Child abuse (choice C) is not the best answer, though it
isn’t unreasonable to have this on your differential when children present with genital or anal complaints. In this case, we have a clear, identifiable cause of the perianal itching. Fecal soilage
(choice D) is part of the differential of anal pruritis and can be due to any cause of diarrhea or loose stools. Some patients have an abnormality with internal anal sphincter relaxation. When anal
itching is otherwise unexplained, this diagnosis should be entertained. Eczema or atopic dermatitis (choice E) is certainly part of the differential diagnosis of anal pruritis, though just the history
does suggest an infectious cause. This familial allergic reaction is often associated with asthma and allergic rhinitis. The rash of eczema is intensely pruritic, and usually appears as erythematous
patches with scaling. In children, eczema usually occurs on the face, scalp, extremities, diaper area and trunk, and usually presents by age 7.
C. Child abuse (choice C) is not the best answer, though it isn’t unreasonable to have this on your differential when children present with genital or anal complaints. In this case, we have a clear,
identifiable cause of the perianal itching.
D. Fecal soilage (choice D) is part of the differential of anal pruritis and can be due to any cause of diarrhea or loose stools. Some patients have an abnormality with internal anal sphincter
relaxation. When anal itching is otherwise unexplained, this diagnosis should be entertained.
E. Eczema or atopic dermatitis (choice E) is certainly part of the differential diagnosis of anal pruritis, though just the history does suggest an infectious cause. This familial allergic reaction is often
associated with asthma and allergic rhinitis. The rash of eczema is intensely pruritic, and usually appears as erythematous patches with scaling. In children, eczema usually occurs on the face,
scalp, extremities, diaper area and trunk, and usually presents by age 7.
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Question # 6
Select the single best answer to the numbered question.
A 66 year old male presents to the emergency department with chest pain. The pain began two hours ago as the patient was watching television. The pain is described as
"squeezing" and is located primarily substernally with radiation to the jaw. Past medical history includes diabetes mellitus, hypertension, hyperlipidemia, and a 50 pack/year smoking
habit. On physical exam, the patient appears anxious and diaphoretic. The patient is given supplemental oxygen by nasal cannula, and aspirin, morphine, and nitroglycerin are
administered. EKG obtained on presentation to the ED is shown. Of the following, which is the most appropriate study to obtain next?
, A. Aortogram
B. Troponin I
C. Stress echo
D. Exercise stress test
E. CT angiogram of chest
You did not answer this question.
Explanations:
A. An aortogram (answer A) used to be the gold standard for the diagnosis of an aortic aneurysm. Now, less-invasive imaging modalities such as CT, MRI, and echo have largely supplanted
aortograms for the diagnosis of aortic dissection. In any case, while aortic dissection ought to be considered in patients with chest pain, this patient’s history is strongly suggestive of ACS, and
this should be investigated first.
B. Key teaching point: To evaluate acute coronary syndrome, you need both an EKG and serial troponins. The patient presents with symptoms highly suggestive of acute coronary syndrome (ACS).
Collectively, ACS consists of three ischemic cardiac disorders: ST-elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI), and unstable angina. Distinguishing
between these entities is important, as both the therapy and the prognosis depends on the diagnosis. The first thing to do when sorting out ACS is to check an EKG – the presence of ST
segment elevation (>1 mm in two or more anatomically contiguous leads) confirms the diagnosis of a STEMI. STEMI carries the worst prognosis of any of any of the acute coronary syndromes,
so finding “tombstones” of ST elevation on EKG is a clear indication for immediate reperfusion therapy, either with thrombolytics or percutaneous interventions in the cath lab. This patient’s EKG
shows little more than normal sinus rhythm. The lack of ST elevation means that the diagnosis of STEMI is ruled out. (As a sidenote: If you answered this question incorrectly because you
thought that there was miniscule ST elevation on this EKG, here is the teaching point for you. When you are looking at an image on the USMLE or shelf exam, whether that image is a CT scan, a
radiograph, or an EKG, expect any abnormalities to be STRIKING. The testmakers do not expect you to be a radiologist or to hold your EKG calipers up to the computer monitor. You need to use
the information from the question stem to know whether you’re looking for a fracture, a head bleed, atrial fibrillation, etc., but so long as you know what to look for, the finding in the image will
either be obvious - or it will be absent.) So now that the patient has a relatively normal EKG, how do we distinguish between the other acute coronary syndromes - NSTEMI and unstable angina?
You need a biomarker to tell you if the patient's cardiac tissue has infarcted, and although you could use CK-MB or LDH, the most sensitive and specific test is cardiac troponins (answer B). If
this patient's troponin I were elevated, it would indicate ischemic necrosis of the myocardium - therefore, the patient is having an MI, even if we don't see it on EKG. The appropriate diagnosis
would thus be NSTEMI. (Pathologically, to have ST segment elevation on EKG requires a full-thickness infarction of the myocardium. If an infarction does not penetrate the entire thickness of the
heart wall, the heart’s electrical conduction is relatively undisturbed and there will not be diagnostic findings on EKG.) The management of NSTEMI is still evolving and remains somewhat
controversial. Reperfusion with primary percutaneous interventions in the cath lab is beneficial for high-risk patients, but thrombolytic therapy carries greater risks and is reserved for those
patients with persisting ST elevations. Many patients with NSTEMI can also be managed medically with antiplatelet therapy and beta blockers. If the patient's troponin I were not elevated, then
the patient has not yet infarcted his myocardium. The diagnosis would therefore be unstable angina, which requires intensive medical management to prevent MI. The patient should be started
on some regimen of heparin, beta blockers, and antiplatelet therapy. The patient should also receive EKG monitoring and serial troponins to ensure that his unstable angina does not eventually
cause infarction. An aortogram (answer A) used to be the gold standard for the diagnosis of an aortic aneurysm. Now, less-invasive imaging modalities such as CT, MRI, and echo have largely
supplanted aortograms for the diagnosis of aortic dissection. In any case, while aortic dissection ought to be considered in patients with chest pain, this patient’s history is strongly suggestive of
ACS, and this should be investigated first. A stress echocardiogram (answer C) or exercise stress test (answer D) might be good tests to risk stratify a medically stable, low-risk patient with
suspected coronary artery disease. This patient, however, requires further evaluation to rule out MI, and stressing the heart is a bad idea in a patient with probable ongoing ischemic pain.
Obtaining a CT pulmonary angiogram (answer E) would be a great test to rule out pulmonary embolism, which can be a cause of chest pain. Here, though, the patient’s history and cardiac risk
factors strongly suggest a cardiac etiology for his pain, so until that is ruled out, searching for a PE is inappropriate.
C. A stress echocardiogram (answer C) or exercise stress test (answer D) might be good tests to risk stratify a medically stable, low-risk patient with suspected coronary artery disease. This patient,
however, requires further evaluation to rule out MI, and stressing the heart is a bad idea in a patient with probable ongoing ischemic pain.
D. A stress echocardiogram (answer C) or exercise stress test (answer D) might be good tests to risk stratify a medically stable, low-risk patient with suspected coronary artery disease. This patient,
however, requires further evaluation to rule out MI, and stressing the heart is a bad idea in a patient with probable ongoing ischemic pain.
E. Obtaining a CT pulmonary angiogram (answer E) would be a great test to rule out pulmonary embolism, which can be a cause of chest pain. Here, though, the patient’s history and cardiac risk
factors strongly suggest a cardiac etiology for his pain, so until that is ruled out, searching for a PE is inappropriate.
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Question # 7
Select the single best answer to the numbered question.
A 73 year old male presents to his physician complaining of cough and fatigue. His cough began 6 months ago and has steadily worsened, and is now associated with occasional
expectoration of mucus streaked with bright red blood. Patient has also noted worsening dyspnea on exertion and a weight loss of 15 lbs. The patient has smoked a pack and a half
of cigarettes every day for the past 60 years. Past medical history is significant for bipolar disorder treated with lithium. Physical exam shows unilateral localized wheezing on the left
chest and clubbing of the distal extremities. Capillary refill is brisk. No skin tenting is observed. Chest X-ray is obtained, which shows a large mass at the left hilum. Labs show:
Glucose 130, Na+ 125, K+ 4.0, Cl- 91, HCO3- 25, BUN 15, Creatinine 1.0; Plasma osmolality 270 (Normal: 282-295 mOsm/kg); Urine osmolality 650 mOsm/kg (Normal: 50 - 1400
mOsm/kg). Which of the following is the most likely mechanism for this patient's hyponatremia?
A. Increased oral intake of hypotonic fluids
B. Decreased oral intake of solutes
C. Impaired secretion of ADH in the posterior pituitary
D. Ectopic overproduction of vasopressin
E. Resistance to ADH action on the cortical and medullary collecting tubules
You did not answer this question.
Explanations:
A. Increased free water intake (answer A) describes the situation seen in psychogenic polydipsia, a disorder in which patients - most commonly schizophrenics receiving antipsychotics - drink
excessive amounts of free water. The kidneys have an incredible capacity for regulating fluids and solutes. Normal patients can excrete more than 10-15 L of urine per day, so for a patient with a
dietary solute intake to become hyponatremic, they would have to have a very impressive water intake!
B. Decreased solute intake (answer B) is the mechanism for “beer potomania,” in which patients drink excessive amounts of beer without taking in enough food to provide adequate solutes. The
minimum urine osmolality is 60mOsm/kg, so there is a certain amount of obligatory solute lost in the urine every day. If a patient is only drinking beer (and massive quantities of it) and not taking
in any solutes, he can deplete his solute reserves over time just through this obligatory solute loss.
C. Answers C and E describe the abnormalities present in diabetes insipidus (DI). DI is a frequently-tested topic on the USMLE, but it is most likely to present with HYPERnatremia, not
HYPOnatremia. There are two types of DI: central and nephrogenic. In central DI (answer C), there is not enough ADH produced by the pituitary, while in nephrogenic DI (answer E), there is end-
organ resistance to ADH action. In either case, the kidney is no longer able to reabsorb H2O from the urine, leading to free water losses and copious polyuria. Since the body is losing more free
water than solute, patients typically become hypernatremic. In children, nephrogenic DI is almost always inherited, while in adults it is commonly caused by drugs - most notably lithium. Central
DI is most commonly caused by surgical trauma to the hypothalamus or pituitary, such as might occur with a trans-sphenoidal removal of a pituitary adenoma.
D. Key teaching point: When you see euvolemic hyponatremia (especially on the USMLE), think SIADH! The constellation of findings in this patient, including euvolemic hyponatremia, hypotonicity
(plasma osmolality <280 mOsms), inappropriately concentrated urine, and normal renal function are diagnostic for the syndrome of inappropriate ADH secretion (SIADH). SIADH has a number of
causes. The most common include: 1) Cancer - ectopic production of ADH by small cell lung cancers or pancreatic malignancies; 2) CNS disturbances - traumatic injuries, strokes, infections, and
hemorrhages can all cause increased ADH production; 3) Drugs - most commonly caused by antipsychotic medications or chemotherapeutics, but the old (and seldom used) insulin
secretagogue chlorpropamide is a commonly-tested causative agent. This question stem is loaded with findings consistent with primary lung carcinoma in general and small cell carcinoma in
particular: a older patient with an extensive smoking history; insidious onset of cough, fatigue, and weight loss; localized wheezing and clubbing of the nails; and a chest x-ray showing a central
mass. Therefore, it is overwhelmingly likely that overproduction of ADH – also known as vasopressin - by the patient's lung tumor is causing his hyponatremia (answer D). Both answers A and B
are plausible explanations for hyponatremia in general. However, as mentioned above, this patient's history and physical exam strongly suggest lung cancer, which is associated with SIADH.
Additionally, either of these situations would be associated with a maximally diluted urine osmolality, while the patient in the question stem has inappropriately concentrated urine. Increased free
water intake (answer A) describes the situation seen in psychogenic polydipsia, a disorder in which patients - most commonly schizophrenics receiving antipsychotics - drink excessive amounts
of free water. The kidneys have an incredible capacity for regulating fluids and solutes. Normal patients can excrete more than 10-15 L of urine per day, so for a patient with a dietary solute intake
to become hyponatremic, they would have to have a very impressive water intake! Decreased solute intake (answer B) is the mechanism for “beer potomania,” in which patients drink excessive
amounts of beer without taking in enough food to provide adequate solutes. The minimum urine osmolality is 60mOsm/kg, so there is a certain amount of obligatory solute lost in the urine every
day. If a patient is only drinking beer (and massive quantities of it) and not taking in any solutes, he can deplete his solute reserves over time just through this obligatory solute loss. Answers C
and E describe the abnormalities present in diabetes insipidus (DI). DI is a frequently-tested topic on the USMLE, but it is most likely to present with HYPERnatremia, not HYPOnatremia. There
are two types of DI: central and nephrogenic. In central DI (answer C), there is not enough ADH produced by the pituitary, while in nephrogenic DI (answer E), there is end-organ resistance to
ADH action. In either case, the kidney is no longer able to reabsorb H2O from the urine, leading to free water losses and copious polyuria. Since the body is losing more free water than solute,
patients typically become hypernatremic. In children, nephrogenic DI is almost always inherited, while in adults it is commonly caused by drugs - most notably lithium. Central DI is most
commonly caused by surgical trauma to the hypothalamus or pituitary, such as might occur with a trans-sphenoidal removal of a pituitary adenoma.
E. Answers C and E describe the abnormalities present in diabetes insipidus (DI). DI is a frequently-tested topic on the USMLE, but it is most likely to present with HYPERnatremia, not
HYPOnatremia. There are two types of DI: central and nephrogenic. In central DI (answer C), there is not enough ADH produced by the pituitary, while in nephrogenic DI (answer E), there is end-
organ resistance to ADH action. In either case, the kidney is no longer able to reabsorb H2O from the urine, leading to free water losses and copious polyuria. Since the body is losing more free
water than solute, patients typically become hypernatremic. In children, nephrogenic DI is almost always inherited, while in adults it is commonly caused by drugs - most notably lithium. Central
DI is most commonly caused by surgical trauma to the hypothalamus or pituitary, such as might occur with a trans-sphenoidal removal of a pituitary adenoma.
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