CNN Exam- Chronic Kidney Disease Questions and Answers Updated 2026

CNN Exam- Chronic Kidney Disease
Questions and Answers Updated
2026
ListMtheMlimitationsMofMtheMmodificationMdietMofMrenalMdiseaseM(MDRD)MandMCockgraft
-GaultMequationsM-
MAnswerMTheMmajorMlimitationMforMbothMequationsMisMthatMatMglomerularMfiltrationMr
atesMaboveM60,MtheirMestimationMisMnotMaccurate.MTheMequationMisMmuchMmoreMaccu
rateMforMstagesMIIMtoMV.



Cockgraft-
GaultMdoesMnotMtakeMintoMaccountMethnicityMorMnutritionalMstatus.MTheMMDRDMisMpre
ferredMbecauseMitMhasMbeenMextensivelyMstudiedMandMtakesMintoMaccountMotherMvariab
les.



MDRDMisMlimitedMinMthatMitMonlyMaccountsMforM1MraceM(black).MOtherMminorityMgrou
psMareMnotMaccountedMforMandMthusMtheirMGFRMmayMnotMbeMtrulyMrepresentative.



***TAKEMAWAY***MBothMareMlessMaccurateMwithMGFRMgreaterMthanM60.



ListMtheMCockgraft-GaultMequationM-MAnswerMCalculatedMbyMtheMfollowing:

(140-
age)MxMleanMbodyMmassM(kg)M/MserumMcreatinineM(mg/dl)MxM72.MTheMequationMisMfu
rtherMmodifiedMbyMmultiplyingMtheMresultMbyM0.85MforMwomanM(asMaMwayMforMaccou
ntingMforMtheMlowerMbodyMmass).



TheMCockgraft-
GaultMequationMisMeasilyMmemorizedMandMonlyMrequiresMoneMbloodMtestMtoMcalculate,
MtheMserumMcreatinine.



LimitedMbyMvariancesMinMtheMbodyMmassM(reliesMonMserumMcreatinineMforMcalculations)
.MCanMbeMoverMorMunderMestimatedMbasedMonMGFR.



ItMalsoMlosesMaccuracyMinMpatientsMwithMamputatedMlimbs,MparticularlyMtheMlowerMextr
emity

, ListMtheMModificationMDietMofMRenalMDiseaseMequationM-
MAnswerMCalculatedMbyMusing:M

(Age)Mexp[-0.176]MxM(BUNM[mg/dl])Mexp[-
0.170]MxM(AlbM[g/dl])Mexp[+0.318]MxM(0.762MifMfemale0MxM(1.18MifMblack)



ComplicatedMequationMandMshouldn'tMbeMmemorized.M

-RegardedMasMbeingMmoreMaccurateMmethod

-WidelyMstudiedMandMalsoMaccountsMforMnutritionMandMethnicity

-LimitationsMincludeMlosingMaccuracyMatMGFRMgreaterMthanM60MandMlabMerrors

-
SerumMBUNMandMalbuminMrequiredMandMifMinaccurateMorMinconsistent,MwillMbeMeffecte
d

-
LimitedMbyMpatientsMwithMunusualMbodyMmassMasMisMseenMwithMobese,Mmalnourished
MandMamputees



DescribeMappropriateMdialysateMcalciumMconcentrationsMinMpatientsMonMeitherMhemodialy
sisMorMperitonealMdialysisM-
MAnswerMTheMdialysateMconcentrationMisMnormallyMsetMtoM2.5MmEq/L.MAtMthisMconcen
tration,MlittleMorMnoMcalciumMisMexchangedMbetweenMdialysateMandMtheMserum.M



InMpatientsMwithMelevatedMcalciumMlevelsMaMlowerMdialysateMconcentrationMwillMbeMne
ededMtoMremoveMexcessMcalcium.MConversely,MifMpatientsMneedMcalcium,MaMdialysateMc
oncentrationMofM3.5MmEq/LMwillMprovideMcalciumMtoMtheMpatient.MInitialMtherapyMtoMr
aiseMtheMserumMcalciumMlevelMisMthroughMbothMcalciumMandMvitaminMDMsupplementati
on.



DescribeMtheMkidney'sMroleMinMcalciumMandMphosphorusMhomeostasisM-
MAnswerMTheMkidneyMisMinstrumentalMinMexcretingMexcessMphosphorousMandMproducing
MtheMactiveMformMofMvitaminMD,McalledMcalcitriol.M



CalcitriolMisMaMhormoneMwhichMtravelsMtoMtheMgutMandMaidsMinMbothMphosphorusMan
dMcalciumMabsorption.MMoreover,McalciumMphosphorusMisMregulatedMbyMtheMhormonesM
PTHM(parathyroidMhormone).MPTHMisMreleasedMfromMtheMparathyroidMglandMandMfunctio
nsMtoMelevateMserumMcalciumMlevelsMandMlowerMphosphorusMlevels.



***NoteMthatMtheMkidneysMareMinvolvedMinMbothMphosphorusMexcretionM(underMinfluen
ceMofMPTH)MandMphosphorusMabsorptionMviaMcalcitriol.