INTRABDOMINAL INFECTIONS, DIARRHEAL INFECTIONS, AND FUO
INTRABDOMINAL INFECTIONS
SPONTANEOUS BACTERIAL PERITONITIS (SBP)
INTRABDOMINAL INFECTIONS OVERVIEW
The intrabdominal infections are infections of the peritoneal cavity and/or of the peritoneal space.
They can be divided into two types, which are:
• Complicated infections: they occur when
infection proceeds beyond organ and causes
either localised or diffuse peritonitis; these may
result in systemic infection, sepsis, and death;
they require both antibiotics and surgical
intervention.
• Uncomplicated infections: they involve single
organ and does not progress to peritoneum;
they are typically treated with antibiotics (e. g.
appendicitis).
Another classification is based on the onset of infection. It can be either community-acquired or
hospital-acquired infections. In the latter case, there is an increased risk of MDR organism infection,
and patients are usually sicker with comorbidities.
The general principles that should be applied for intrabdominal infections are three, which are source
control, empiric antibiotic therapy, and fluid support. Based then on microbiological culture the
reassessment of the antibiotic therapy is performed. Reintervention is required is the infection is
ongoing and does not respond to the therapy.
CLINICAL CASE - 1
A 52-year-old male is hospitalised for 3 days with abdominal pain and fever. He has a history of
decompensated alcoholic cirrhosis and ascites managed with diuretics. His medications are
furosemide, spironolactone, and lactulose. Vitals are notable for a T of
38°C, BP 115/60mmHg, and HR 110bpm. His abdomen is distended
and moderately tender to palpation with a positive fluid wave (used
to assess presence of fluid in abdomen). Lab studies show:
• Bilirubin 4.5mg/dL.
• Serum creatinine 1.3mg/dL.
• WBC 12,000/L.
DIAGNOSIS AND TYPES OF PERITONITIS
The patient suffers from a bacterial peritonitis. The peritonitis can be divided into three types, which
are:
• Primary peritonitis (or spontaneous bacterial peritonitis,
SBP): it is characterised in no loss of GI tract integrity; it is
observed in infants (after pneumococcal infection) and
cirrhotic patients.
• Secondary peritonitis: it is the most common infection; it is
an acute infection due to visceral perforation, ulceration, or
direct infection; the CT scan with contrast medium is used
to detect the perforation and the infection; anastomotic
dehiscence are common causes of peritonitis in the post-
operative period (e. g. Roux-en-Y bypass).
• Tertiary peritonitis: it is an ongoing stage of infection when peritonitis persists or recurs, often
due to low-virulence organisms or MDR pathogens.
,A possible consequence of peritonitis can be intraperitoneal abscess. It occurs secondarily as a
consequence of disease organ, penetrating trauma or surgical procedure.
RISK FACTORS AND ASCITES
The most common risk factors for SBP are liver cirrhosis and ascites. The SBP is present in about 10%
of patients admitted to the hospital with cirrhotic ascites. Other risk factors include concomitant GU
bleeds, previous peritonitis, and low ascitic protein concentrations.
Ascetic patients are immunocompromised due to gut dysbiosis,
systemic inflammation, immune paralysis, and bacterial translocation
into bloodstream (i. e. leaky gut).
In children, haematogenous spread of S. pneumoniae and other
streptococci are the most common cause of SBP. The Staphylococcus
aureus is rarely isolated (MRSA is not the main causative agent).
In case of liver cirrhosis, the albumin production is decreased, which
results in a decreased plasma oncotic pressure. Since fluids move more
in the interstitium, there is a reduction in the blood volume and
pressure, which activates the RAAS. The aldosterone promotes salt
and water retention increasing the blood volume and pressure.
However, since in the liver portal hypertension is present, the
increased pressure will result in accumulation of fluids in the
peritoneal space (i. e. ascites). The ascites can turn into peritonitis
once the bacteria of the intestine are moved within the peritoneal space due to leaky gut, or via the
rupture of lymphatics that are carrying the contaminated lymph.
SYMPTOMS AND DIAGNOSIS
The clinical presentations of SBP are:
• Fever (69%).
• Altered mental status (59%).
• Abdominal tenderness (49%).
• Diarrhoea (32%).
• Paralytic ileus (30%).
• Hypotension (21%).
• Hypothermia (17%).
The diagnosis and management are based on three steps, which are:
1. Ultrasound/CT and diagnostic paracentesis.
2. Start empiric therapy.
3. Analyse ascitic fluid: albumin, total protein, cell count and culture.
SECONDARY PERITONITIS
The secondary peritonitis should be assessed with abdominal CT with contrast medium. If thickening
of the visceral and parietal peritoneum is observed, secondary peritonitis is diagnosed. In some cases,
few locules of air are present in the peritoneum due to prior
paracentesis.
The paracentesis is the procedure by which the peritoneal fluid
is taken from the peritoneal cavity. Once collected, it is sent to
labs to obtain CBC with differential analysis of ascites fluid, cell
count and differential, Gram-stain and bacterial cultures, total
protein, albumin, glucose, and lactose dehydrogenase.
An important finding is albumin. Indeed, based on the serum-
ascites albumin gradient (SAAG) is possible to evaluate possible
patients’ conditions, which are:
, • High albumin gradient (SAAG >1.1g/dL): it is a sign of cirrhosis, alcoholic hepatitis, heart
failure, and massive hepatic metastasis.
• Low albumin gradient (SAAG<1.1g/dL): it is a sign of peritoneal carcinomatosis, peritoneal
tuberculosis, pancreatitis, serositis, and nephrotic syndrome.
TYPES OF PERITONITIS BASED ON LAB TESTS
The analysis of the ascites fluid can provide information regarding the type of infection that is present.
Based on lab analysis five types of peritonitis can be diagnosed, which are:
• Primary peritonitis: it is furtherly divided into four types, which are:
Typical ABS: it presents elevated PMN (>250), low protein count (<1g/dL), high
glucose levels (>2.8mmol/L); it is typically monobacterial, caused by either Gram-
positive or Gram-negative; blood culture results positive in 75% of cases.
Culture-negative neutrocytic ascites (CNNA): it presents elevated PMN (>250),
variable protein count and glucose levels; it is caused by Gram-negative and blood
culture results negative.
Monomicrobial non-neutrocytic bacteriascites (MNNB): it presents low PMN (<250),
normal protein count and glucose levels; it is typically monomicrobial, caused by
either Gram-positive or Gram-negative; blood culture results negative.
Polymicrobial ascites (PBA): it presents low PMN (<250), normal protein count and
glucose levels; it is typically polymicrobial, caused mainly by Gram-positive; blood
culture results negative.
• Secondary peritonitis: it presents elevated PMN (>250), high protein count (>1g/dL), and low
glucose level (<2.8mmol/L); it is typically polymicrobial and caused by either Gram-positive or
Gram-negative; the culture is usually negative.
• Tertiary peritonitis: it presents elevated PMN (>250), variable protein count and variable
glucose level; it is typically polymicrobial and caused by either Gram-positive or Gram-
negative; the culture is usually negative.
• Peritoneal dialysis (PD): it presents elevated PMN (>100), variable protein count and variable
glucose level; it is typically polymicrobial and caused by Gram-positive; the culture is usually
negative.
• Tuberculosis (TB): it presents elevated lymphocytes (150-4000), high protein count (>3g/dL),
and low glucose level; it is monomicrobial, and caused by Gram-negative; the culture is
usually negative.
WBC Total Blood
TYPE Glucose Organism Gram
count protein culture
Mono- 75%
Typical PMN>250 <1g/dL >2.8mmol/L Variable
microbial positive
CNNA PMN>250 Variable Variable Variable Negative Negative
Primary
Mono-
peritonitis MNBA PMN<250 Normal Normal Variable Negative
microbial
Poly-
PBA PMN<250 Normal Normal Positive Negative
microbial
Poly-
Secondary peritonitis PMN>250 >1g/dL <2.8mmol/L Positive Negative
microbial
Poly-
Tertiary peritonitis PMN>250 Variable Variable Variable Negative
microbial
Peritoneal dialysis Mono-
PMN>100 Variable Variable Positive Negative
(PD) microbial
Lym>150- Mono-
Tuberculosis (TB) >3g/dL Low Negative Negative
4000 microbial
INTRABDOMINAL INFECTIONS
SPONTANEOUS BACTERIAL PERITONITIS (SBP)
INTRABDOMINAL INFECTIONS OVERVIEW
The intrabdominal infections are infections of the peritoneal cavity and/or of the peritoneal space.
They can be divided into two types, which are:
• Complicated infections: they occur when
infection proceeds beyond organ and causes
either localised or diffuse peritonitis; these may
result in systemic infection, sepsis, and death;
they require both antibiotics and surgical
intervention.
• Uncomplicated infections: they involve single
organ and does not progress to peritoneum;
they are typically treated with antibiotics (e. g.
appendicitis).
Another classification is based on the onset of infection. It can be either community-acquired or
hospital-acquired infections. In the latter case, there is an increased risk of MDR organism infection,
and patients are usually sicker with comorbidities.
The general principles that should be applied for intrabdominal infections are three, which are source
control, empiric antibiotic therapy, and fluid support. Based then on microbiological culture the
reassessment of the antibiotic therapy is performed. Reintervention is required is the infection is
ongoing and does not respond to the therapy.
CLINICAL CASE - 1
A 52-year-old male is hospitalised for 3 days with abdominal pain and fever. He has a history of
decompensated alcoholic cirrhosis and ascites managed with diuretics. His medications are
furosemide, spironolactone, and lactulose. Vitals are notable for a T of
38°C, BP 115/60mmHg, and HR 110bpm. His abdomen is distended
and moderately tender to palpation with a positive fluid wave (used
to assess presence of fluid in abdomen). Lab studies show:
• Bilirubin 4.5mg/dL.
• Serum creatinine 1.3mg/dL.
• WBC 12,000/L.
DIAGNOSIS AND TYPES OF PERITONITIS
The patient suffers from a bacterial peritonitis. The peritonitis can be divided into three types, which
are:
• Primary peritonitis (or spontaneous bacterial peritonitis,
SBP): it is characterised in no loss of GI tract integrity; it is
observed in infants (after pneumococcal infection) and
cirrhotic patients.
• Secondary peritonitis: it is the most common infection; it is
an acute infection due to visceral perforation, ulceration, or
direct infection; the CT scan with contrast medium is used
to detect the perforation and the infection; anastomotic
dehiscence are common causes of peritonitis in the post-
operative period (e. g. Roux-en-Y bypass).
• Tertiary peritonitis: it is an ongoing stage of infection when peritonitis persists or recurs, often
due to low-virulence organisms or MDR pathogens.
,A possible consequence of peritonitis can be intraperitoneal abscess. It occurs secondarily as a
consequence of disease organ, penetrating trauma or surgical procedure.
RISK FACTORS AND ASCITES
The most common risk factors for SBP are liver cirrhosis and ascites. The SBP is present in about 10%
of patients admitted to the hospital with cirrhotic ascites. Other risk factors include concomitant GU
bleeds, previous peritonitis, and low ascitic protein concentrations.
Ascetic patients are immunocompromised due to gut dysbiosis,
systemic inflammation, immune paralysis, and bacterial translocation
into bloodstream (i. e. leaky gut).
In children, haematogenous spread of S. pneumoniae and other
streptococci are the most common cause of SBP. The Staphylococcus
aureus is rarely isolated (MRSA is not the main causative agent).
In case of liver cirrhosis, the albumin production is decreased, which
results in a decreased plasma oncotic pressure. Since fluids move more
in the interstitium, there is a reduction in the blood volume and
pressure, which activates the RAAS. The aldosterone promotes salt
and water retention increasing the blood volume and pressure.
However, since in the liver portal hypertension is present, the
increased pressure will result in accumulation of fluids in the
peritoneal space (i. e. ascites). The ascites can turn into peritonitis
once the bacteria of the intestine are moved within the peritoneal space due to leaky gut, or via the
rupture of lymphatics that are carrying the contaminated lymph.
SYMPTOMS AND DIAGNOSIS
The clinical presentations of SBP are:
• Fever (69%).
• Altered mental status (59%).
• Abdominal tenderness (49%).
• Diarrhoea (32%).
• Paralytic ileus (30%).
• Hypotension (21%).
• Hypothermia (17%).
The diagnosis and management are based on three steps, which are:
1. Ultrasound/CT and diagnostic paracentesis.
2. Start empiric therapy.
3. Analyse ascitic fluid: albumin, total protein, cell count and culture.
SECONDARY PERITONITIS
The secondary peritonitis should be assessed with abdominal CT with contrast medium. If thickening
of the visceral and parietal peritoneum is observed, secondary peritonitis is diagnosed. In some cases,
few locules of air are present in the peritoneum due to prior
paracentesis.
The paracentesis is the procedure by which the peritoneal fluid
is taken from the peritoneal cavity. Once collected, it is sent to
labs to obtain CBC with differential analysis of ascites fluid, cell
count and differential, Gram-stain and bacterial cultures, total
protein, albumin, glucose, and lactose dehydrogenase.
An important finding is albumin. Indeed, based on the serum-
ascites albumin gradient (SAAG) is possible to evaluate possible
patients’ conditions, which are:
, • High albumin gradient (SAAG >1.1g/dL): it is a sign of cirrhosis, alcoholic hepatitis, heart
failure, and massive hepatic metastasis.
• Low albumin gradient (SAAG<1.1g/dL): it is a sign of peritoneal carcinomatosis, peritoneal
tuberculosis, pancreatitis, serositis, and nephrotic syndrome.
TYPES OF PERITONITIS BASED ON LAB TESTS
The analysis of the ascites fluid can provide information regarding the type of infection that is present.
Based on lab analysis five types of peritonitis can be diagnosed, which are:
• Primary peritonitis: it is furtherly divided into four types, which are:
Typical ABS: it presents elevated PMN (>250), low protein count (<1g/dL), high
glucose levels (>2.8mmol/L); it is typically monobacterial, caused by either Gram-
positive or Gram-negative; blood culture results positive in 75% of cases.
Culture-negative neutrocytic ascites (CNNA): it presents elevated PMN (>250),
variable protein count and glucose levels; it is caused by Gram-negative and blood
culture results negative.
Monomicrobial non-neutrocytic bacteriascites (MNNB): it presents low PMN (<250),
normal protein count and glucose levels; it is typically monomicrobial, caused by
either Gram-positive or Gram-negative; blood culture results negative.
Polymicrobial ascites (PBA): it presents low PMN (<250), normal protein count and
glucose levels; it is typically polymicrobial, caused mainly by Gram-positive; blood
culture results negative.
• Secondary peritonitis: it presents elevated PMN (>250), high protein count (>1g/dL), and low
glucose level (<2.8mmol/L); it is typically polymicrobial and caused by either Gram-positive or
Gram-negative; the culture is usually negative.
• Tertiary peritonitis: it presents elevated PMN (>250), variable protein count and variable
glucose level; it is typically polymicrobial and caused by either Gram-positive or Gram-
negative; the culture is usually negative.
• Peritoneal dialysis (PD): it presents elevated PMN (>100), variable protein count and variable
glucose level; it is typically polymicrobial and caused by Gram-positive; the culture is usually
negative.
• Tuberculosis (TB): it presents elevated lymphocytes (150-4000), high protein count (>3g/dL),
and low glucose level; it is monomicrobial, and caused by Gram-negative; the culture is
usually negative.
WBC Total Blood
TYPE Glucose Organism Gram
count protein culture
Mono- 75%
Typical PMN>250 <1g/dL >2.8mmol/L Variable
microbial positive
CNNA PMN>250 Variable Variable Variable Negative Negative
Primary
Mono-
peritonitis MNBA PMN<250 Normal Normal Variable Negative
microbial
Poly-
PBA PMN<250 Normal Normal Positive Negative
microbial
Poly-
Secondary peritonitis PMN>250 >1g/dL <2.8mmol/L Positive Negative
microbial
Poly-
Tertiary peritonitis PMN>250 Variable Variable Variable Negative
microbial
Peritoneal dialysis Mono-
PMN>100 Variable Variable Positive Negative
(PD) microbial
Lym>150- Mono-
Tuberculosis (TB) >3g/dL Low Negative Negative
4000 microbial
