Which of the following is most likely cause of ARF in patient with renal failure index <1?
Correct Answer: Congestive cardiac failure
Description: Ans. b (Congestive Cardiac Failure) (Ref. Harrison 18th/ p 1649; Table 260-3)CAUSES OFARFA. Diseases that cause renal hypoperfusion without compromising the integrity of renal parenchyma (prerenal ARF, prerenal azotemia) (-55%);B. Diseases that directly involve renal parenchyma (intrinsic renal ARF, renal azotemia) (-40%); andC. Diseases associated with urinary tract obstruction (postrenal ARF, postrenal azotemia) (-5%).CAUSES OFARFPrerenal causes# Volume depletion# Decreased "effective" circulatory volume (e.g., heart failure, liver failure),# Treatment with NSAIDs or ACE inhibitorsIntrinsic renal ARF# Diseases involving large renal vessels- Renal artery thrombosis- Atheroembolism- Renal vein thrombosis# Diseases of small vessels and glomeruli- Glomerulonephritis/ vasculitis- Hemolytic-uremic syndrome/thrombotic thrombocytopenic purpura- Malignant hypertension# ARF mediated by ischemia or toxins (ATN)- Ischemia- Exogenous toxins, e.g., Recent radiocontrast study, nephrotoxic antibiotics or anticancer agents often coexistent with volume depletion, sepsis, or chronic renal insufficiency- Endogenous toxins, e.g., history suggestive of rhabdomyolysis (seizures, coma, ethanol abuse, trauma), History suggestive of hemolysis (blood transfusion)- History suggestive of tumor lysis (recent chemotherapy), myeloma (bone pain), or ethylene glycol ingestion# Acute diseases of the tubulointerstitium- Allergic interstitial nephritis- Acute bilateral pyelonephritis Diagnostic IndexTypical findings in ARF PrerenalIntrinsic RenalFractional excretion of sodium (%) UNa x Pcr-----PNa x Ucrx 100<1>1Urine sodium concentration (mmol/L)<10>20Urine creatinine to plasma creatinine ratio>40<20Urine urea nitrogen to plasma urea nitrogen ratio>8<3Urine specific gravity>1.020-1.010Urine osmolality (mOsm/kg H20)>500-300Plasma BUN/creatinine ratio>20<10-15Renal failure index<1>1UNa---Ucr/Pcr Urinary sedimentHyaline castsMuddy brown granular castsAlso know:More than 70% of kidney function must be lost before features of renal failure become evident
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