The document provides an overview of acute renal failure for medical interns, discussing key points to consider such as causes, classifications, diagnostic testing, management, and prognosis. It classifies acute renal failure into pre-renal, intrinsic renal, and post-renal causes and emphasizes the importance of establishing the cause through history, physical exam, and urine/lab studies to guide treatment and predict outcomes.

1. Acute Renal Failure for the Intern Things to think about before you call that consult… Vimal Derebail, MD Renal Fellow UNC Division of Nephrology and Hypertension

18. Acute Renal Failure <20 >40 Urine Cr ./Plasma Cr. ≤ 20:1 >20:1 BUN/Creatinine >50% <35% FE Urea ≥ 1% <1% FE Na >40 mEq/L <20 mEq/L Urine Na ATN Pre-Renal Index

23. Acute Renal Failure UpToDate Images. Waxy Casts: Smooth appearance. Blunt ends. May have a “crack”. Felt to be last stage of degenerating cast – representative of chronic disease. Granular Casts: Represent degenerating cellular casts or aggregated protein. Nonspecific.

24. Acute Renal Failure Fatty Casts: Seen in patients with significant proteinuria. Refractile in appearance. May be associated with free lipid in the urine. Can see also “oval fat bodies” – RTE’s that have ingested lipid. Polarize – demonstrate “Maltese cross”. UpToDate Images.

25. Acute Renal Failure Muddy Brown Casts: Highly suggestive of ATN. Pigmented granular casts as seen in hyperbilirubinemia can be confused for these. UpToDate Images.

26. Acute Renal Failure UpToDate Images. White Blood Cell Casts: Raises concern for interstitial nephritis. Can be seen in other inflammatory disorders. Also seen in pyelonephritis.

28. Acute Renal Failure Red Blood Cell Casts: Essentially diagnostic of vasculitis or glomerulonephritis. Dysmorphic Red Cells: Suggestive of glomerular bleeding as seen with glomerulonephritis. Blebs, buds, membrane loss. Rarely reported in other conditions – DM, ATN.

29. Acute Renal Failure Crystals – Pretty and important. Uric acid crystals: Seen in any setting of elevated uric acid and an acidic urine. Seen with tumor lysis syndrome. Calcium oxalate crystals: Monohydrate – dumbell shaped, may be needle-like. Dihydrate – envelope shaped. Form independent of urine pH. Seen acutely in ethylene glycol ingestion. UpToDate Images.