Approach to laboraratory diagnosis of acute and chronic renal failure

• 1. Laboratory approach for diagnosisof Acute and Chronic Renal FailureSpeaker :-Dr. Adrija Pathak

2. Acute renal Failure Rapid deterioration of renal function (GFR) over aperiod of hours to days Azotemia (accumulation of nitrogenous wastes) Decreased urine output (usually but not always)Oliguria: /= 90 with proteinuria,abnormal blood & urinechemistry, imaging studies2 60- 893 30- 594 15- 295 2ml/min- Expressed as a percentage of average normal- Formula is 1.33 x UV/P Standard urea clearance : 40 -65 ml (average : 54 ml)- Formula is 1.85 x UV/P Two urine sample collected. If difference in clearanceexceed 10% repeat the test 15. Creatinine measurement Based on Jaffe reaction- reaction of creatininewith trinitrophenol (picric acid) in alkalinecondition to form a red complex. OD measured at520nm Alkaline Picrate Method Several chromogens ketones, glucose,fructose, urea, ascorbic acid , guanidine,pyruvate(also protein) react with picrate and gives falsehigh value Bilirubin and hemoglobin interfere giving false lowvalue Without removing chromogens upper limt ofnormal measured by jaffe reaction is1.6-1.9 mg/dlfor adults 16. Automated method-based on jaffe reaction principleusing autoanalyser equipped with a thermocuvette(30C) 1st reading recorded at 20 second as most ofinterfering chromogen react fast Creatinine and alkaline picrate react relatively slowly.Hence 2nd reading noted after 80 seconds Same procedure is used for a standardCreatinine (mg/dl)= OD T(80sec) OD T(20sec) xconc. of stdOD S(80sec) OD S(20sec) Reference Range 1-5 yr 0.3- 0.5 mg/dl5-10 yr 0.5- 0.8 mg/dlAdult male 0.6-1.2mg/dl 17. Measurement of urea/ urea nitrogen Gold standard is isotope dilution massspectrometry- used only as reference method colorimetric method based on reaction of ureawith diacetyl monoxime under strong acidiccondition in the presence of ferric ions andthiosemicarbazide to form intense red colouredwhich is measured at 540nm. normal range birth to 1 yr 4-16mg/dl1-40 yr 7-21 mg/dlGradual slight increase over 40 yrPossible panic range BUN>100mg/dl 18. enzymatic method- berthelot method- urease splits urea into ammonia& CO2. ammonia reacts with phenol in presence ofhypochlorite to form indophenol which with alkaligives a blue coloured compound whose OD can bemeasured at 546nm- UV Kinetic method- after hydrolyses by urease, inthe presence ammonia, ketoglutarate &glutamate dehydrogenase, NADH is oxidised toNAD+. The rate of decrease of OD is measured atan interval of 30 sec at 340 nm which is ureaconcentration. 19. UrinanalysisPhysical Chemical MicroscopyVolume (1200-1500ml/d)Protein Leukocyte/ Pus cellColour Glucose ErythrocyteApperance (clear) Ketone bodies Epithelial cellsSediment Occult blood CastsOdor Bile pigment CrystalsReaction/pH (acidic 4.7-7.5)Bile salt Yeast/Bacteria/spermatozoaSpecific gravity (1.003-1.030)urobilinogen 20. Specific gravity Urinometer-vessel is filled 3/4th with urine (min 15mlis required)urinometer inserted without touching theside/bottom. Lower meniscus is read.- Checked daily by measuring sp. Gravity of distilledwater- Correction for temperature/protein/glucose Reagent strip Refractometer Falling drop method 21. Albuminuria Helpful in monitoring nephron injury & responseto therapy especially in chronic glomerulardiseases 24 Hour urine collection is gold standard Albumin/ creatinine ratio in a spot first morningurine sample is practical and correlates well Persistence of >17mg albumin/gram of creatininein male or >25 mg albumin/gram of creatinine infemale signifies chronic renal damage 22. Microscopic findingsHyaline Casts:Better seen with low light.Non-specific.Composed of Tamm-Horsfall mucoprotein. 23. Granular Casts:Represent degeneratingcellular casts oraggregated protein.Nonspecific.Waxy Casts:Smooth appearance.Blunt ends.Felt to be last stage ofdegenerating cast representative of chronicdisease. 24. Muddy BrownCasts:Highlysuggestive ofATN.Pigmentedgranular casts asseen inhyperbilirubinemia can beconfused forthese. 25. Fatty Casts:Seen in patients withsignificant proteinuria.Refractile in appearance.May be associated withfree lipid in the urine.Can see also oval fatbodies RTEs thathave ingested lipid. 26. HematuriaNonglomerular hematuria:Urologic causes.Bladder/Foley trauma.Nephrolithiasis.Urologic malignancy.May be crenated based uponage of urine, osmolality NOTdysmorphic. 27. Dysmorphic Red Cells:Suggestive ofglomerular bleeding asseen withglomerulonephritis.Blebs, buds, membraneloss.Rarely reported in otherconditions DM, ATN.Red Blood CellCasts:Essentially diagnosticof vasculitis orglomerulonephritis. 28. CrystalsUric acid crystals:Seen in any setting ofelevated uric acid and anacidic urine.Seen with tumor lysissyndrome.Calcium oxalate crystals:Monohydrate dumbellshaped, may be needle-like.Dihydrate envelopeshaped.Form independent of urinepH.Seen acutely in ethyleneglycol ingestion. 29. Prerenal ARF sediment is characteristically acellularand contain hyaline cast Post renal failure may present with inactivesediment, although pyuria and hematuria arecommonCasts Pigmented muddy brown cast cast containingtubular epithelial cell characteristic of ATN RBC cast- glomerular injury/ acute tubulointerstitialnephritis WBC cast & nonpigmented granular cast- interstitialnephritis Broad granular cast- chronic renal disease 30. Eosinophiluria (>5% of urine leukocyte) is acommon finding in antibiotic induced allergicinterstitial nephritis and can be detected by Haselsstain Atheroembolic RF have eosinophill-richinflammatory rxn but normal urinanalysis or feweosinophils seen Lymphocyte may predominate in allergic interstitialnephritis by NSAIDs, ampicillin, rifampicin,interferone alpha. Proteinurea >1g/d suggests injury to gl.Ultrafiltration/ excretion of myeloma light chain Hemoglobinuria or myooglobinurea should besuspected if urine is strongly +ve for heme bydipstick but show few RBC 31. Fractional excretion Quantity of substance excreted in urine expressed asfraction of filtered load of same substanceFE = (Ux/Px). (Pcreat/ Ucreat) When the subtance excreted in urine has clearanceless than that of creatinine FE< 1 FE of sodium is used to distinguish betweenATN(>1%) and prerenal azotemia (20:1 10 -15:1Urine sodium (U Na), meq/L 40Urine Osmolality, mosmol/LH2O>500 40