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RenalMain1-10Q1An18-year-oldgirlcomestotheemergencydepartmentwithanew-onsetskinrashandmalaise.Sheisconcernedasheraunthaslupustreatedwithcorticosteroids.Hermedicalhistoryisunremarkableexceptfordysuriaandincreasedurinaryfrequencyaweekago,whichwaseffectivelytreatedwithsulfamethoxazofe-trimethoprim.Thepatienttakesnomedicationsandusesnoillicitdrugs.Shehashadthesamesexualpartnerforthepast4months.Hertemperatureis38.0℃(100.4℉):pulseis86/min:andrespirationsare16/min.Physicalexaminationrevealsadisseminatedmaculopapularrash.Thereisnocostovertebraltenderness.Thepatienthasnojointswellingoreffusion.Herserumcreatinineis2.0mg/dL.Urinalysisreveals2-5redbloodcells/hpf:numerouswhitebloodcellcasts,andmildproteinuria.Whichofthefollowingisthemostlikelydiagnosis?A.DisseminatedgonococcemiaB.InterstitialnephritisC.LupusnephritisD.PostinfectiousacuteglomerulonephritisE.PyelonephritisA1Correctanswer:BTheclinicalpresentationistypicalofallergicinterstitialnephritis(AIN):acuterenalfailure,fever,rash,arecenthistoryofpara-aminobenzoicacidanalogueantibiotic(sulfonamide)ingestion,andwhitebloodcell(WBC)castsonurinalysis.Patientsmayalsohavearthralgiasandeosinophiluria.Symptomsusuallyappear5daystoseveralweeksafteruseofanoffendingagent.DrugscausethemajorityofAINcases;examplesincludeantibiotics(eg,penicillins,cephalosporins,trimethoprim,rifampin),nonsteroidalanti-inflammatorydrugs,anddiuretics.Lesscommonly,AINmaybecausedbyinfectiousagents(eg,Legionella,Mycobacteriumtuberculosis,Streptococcus).(ChoiceA)Disseminatedgonococcemiacausesavesicopustularrash.RenalfailurewithWBCcastsisnotusuallyseen.(ChoiceC)Themucocutaneousmanifestationsoflupusincludemalarrashanddiscoidrash,butthispatienthasamaculopapularrash.Lupusnephritisischaracterizedbyhypertension,mildproteinuria,andredbloodcell(RBC)casts.(ChoiceD)Postinfectiousglomerulonephritisproduceshematuria,mildproteinuria,RBCcasts,andfluidretentionresultinginhypertensionandperiorbitaledema.Itusuallyoccurs1-2weeksafteranepisodeofstreptococcalpharyngitis/skininfectionandnotafteraurinaryinfection.(ChoiceE)pyelonephritiscancomplicateuntreatedcystitis,butmanifestswithchills,fever,andtendernessintheflanksand/orthecostovertebralangle.Disseminatedrashisnotusuallyseen.Educationalobjective:Drug-inducedinterstitialnephritisisusuallycausedbyantibiotics(eg,penicillins,cephalosporins,trimethoprim,rifampin),nonsteroidalanti-inflammatorydrugs,anddiuretics.Patientspresentwithafever,maculopapularrash,andrenalfailure.Urinalysismayrevealwhitebloodcellcastsand,iessfrequently,eosinophils.Q2A55-year-oldmanisbeingevaluatedforfatigue.HehasahistoryofhypertensionandchroniclowbackpainduetoatraumaticInjury20yearsago.Hismedicationsincludelisinoprilandover-the-counterpainmedications.Hisfatherhasdiabetesandhismotherhashypertension.Hedoesnotusetobacco,alcohol,orillicitdrugs.Hisbloodpressureis130/80mmHgandpulseis30/min.Physicalexaminationisunremarkable.Laboratorystudiesareasfollows:Laboratorystudiesshowserumcreatininelevelof2.2mg/dLandbloodureanitrogenof34mg/dL.Whichofthefollowingisthemostlikelycauseofthispatient'surinaryfindings?A.GlomerulonephritisB.NephrolithiasisC.TubulointerstitialnephritisD.UrinarytractinfectionE.UrothelialmalignancyA2Correctanswer:CThispatient'sabnormalurinalysis(painlesshematuria,sterilepyuria,whitebloodceilcasts,traceproteinuria)suggestsanon-glomeru!ardisorderaffectingthetubulointerstitiumorliningoftheurinarytract.Givenhischroniclowbackpaintreatedwithover-the-counteranalgesics,helikelyhasanalgesicnephropathy.Chronicanalgesicusewith1ormoreanalgesics(eg,nonsteroidalanti-inflammatorydrugsuchasaspirin)cancausechronickidneydiseaseduetochronictubulointerstitialnephritis.Patientsaretypicallyasymptomaticwithanelevatedcreatininefoundincidentally.Patientscanalsodeveloppainlessandprominenthematuriaduetopapillaryischemiafromanalgesic-inducedvasoconstrictionofmedullarybloodvessels(vasarecta).Significantpapillarynecrosisandsloughingmaycauserenalcolic.(ChoiceA)Glomerulonephritisistypicallyaccompaniedbymorecharacteristicabnormalitiesseenonurinestudies(dysmorphicredbloodcells,subnephrotic/nephroticrangeproteinuria,andredbloodcellcasts).However,thispatient'spredominantpresenceofurinewhitebloodcellssuggestsaninterstitialnephritis.(ChoiceB)Nephrolithiasisusuallypresentswithrenalcolicaccompaniedbyhematuria.However,nephrolithiasisistypicallynotassociatedwithtraceproteinuria,pyuria,oracutekidneyinjuryunlessthereisinfectionorbilateralobstruction.(ChoiceD)Urinarytractinfectionpresentswithdysuria,fever/chiils,abdominalpain,andpyuria(withpositiveleukocyteesteraseornitrite).(ChoiceE)Malignancytypicallypresentswithpainlesshematuriabutislesslikelyinthispatientwithouttobaccouseorfamilyhistoryofcancer.Urothelialmalignancyrarelycausestraceproteinuria,pyuria,orchronickidneydisease.Educationalobjective:Long-termanalgesicusewith1ormoreanalgesics(eg,nonsteroidalanti-inflammatorydrugsuchasaspirin)cancausechronickidneydiseaseduetotubulointerstitialnephritisandhematuriaduetopapillarynecrosis.Q3A55-year-oldwomancomestothephysicianforanannualphysicalexamina