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Acute Renal Failure

Acute Renal Failure. Malcolm Cox, M.D. Acute Renal Failure Definition. Acute decrement in GFR May heal partially or completely or progress to more severe renal insufficiency, including end-stage renal disease. Review. 9.0. 8.0. Serum Creatinine (mg/dl). 7.0. 6.0. 5.0. 4.0. 3.0. 2.0.

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Acute Renal Failure

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  1. Acute Renal Failure Malcolm Cox, M.D.

  2. Acute Renal FailureDefinition • Acute decrement in GFR • May heal partially or completely or progress to more severe renal insufficiency, including end-stage renal disease

  3. Review 9.0 8.0 Serum Creatinine (mg/dl) 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0 0 20 40 60 80 100 120 140 160 180 Inulin Clearance (ml/min per 1.73m2)

  4. Acute Renal FailureClassification • Pre-renal (functional) • Renal (structural) • Post-renal (obstruction)

  5. Acute Renal FailurePre-renal Causes • Intravascular volume depletion • Hemorrhage • Sodium depletion • Redistribution of ECF • “Third space” accumulation • Edematous disorders • Drugs

  6. RAP RAP – RVP ~ RBF RBF = Raff + Reff Raff + Reff Review Renal Blood Flow F = P/R

  7. Review Raff Reff PGC RAP

  8. Pre-Renal AzotemiaPathophysiology • Renal hypoperfusion • Decreased RBF and GFR • Increased filtration fraction (GFR/RBF) • Increased Na and H2O reabsorption • Oliguria, high Uosm, low UNa • Elevated BUN/Cr ratio

  9. Acute Tubular NecrosisClassification • Ischemic • Nephrotoxic

  10. Acute Tubular Necrosis

  11. Acute Tubular Necrosis

  12. Acute Renal FailureNephrotoxic ATN • Endogenous Toxins • Heme pigments (myoglobin, hemoglobin) • Myeloma light chains • Exogenous Toxins • Antibiotics (e.g., aminoglycosides, amphotericin B) • Radiocontrast agents • Heavy metals (e.g., cis-platinum, mercury) • Poisons (e.g., ethylene glycol)

  13. Acute Tubular Necrosis

  14. Acute Tubular Necrosis

  15. Acute Interstitial NephritisCauses • Allergic interstitial nephritis • Drugs • Infections • Bacterial • Viral • Sarcoidosis

  16. Allergic Interstitial NephritisClinical Characteristics • Fever • Rash • Arthralgias • Eosinophilia • Urinalysis • Microscopic hematuria • Sterile pyuria • Eosinophiluria

  17. Acute Interstitial Nephritis

  18. Cholesterol Embolization

  19. Contrast-Induced ARFPrevalence • Less than 1% in patients with normal renal function • Increases significantly with renal insufficiency

  20. Contrast-Induced ARFRisk Factors • Renal insufficiency • Diabetes mellitus • Multiple myeloma • High osmolar (ionic) contrast media • Contrast medium volume

  21. Contrast-induced ARFClinical Characteristics • Onset - 24 to 48 hrs after exposure • Duration - 5 to 7 days • Non-oliguric (majority) • Dialysis - rarely needed • Urinary sediment - variable • Low fractional excretion of Na

  22. Contrast-induced ARFProphylactic Strategies • Use I.V. contrast only when necessary • Hydration • Minimize contrast volume • Low-osmolar (nonionic) contrast media • N-acetylcysteine, fenoldopam

  23. Acute Renal FailurePost-renal Causes • Intra-renal Obstruction • Acute uric acid nephropathy • Drugs (e.g., acyclovir) • Extra-renal Obstruction • Renal pelvis or ureter (e.g., stones, clots, tumors, papillary necrosis, retroperitoneal fibrosis) • Bladder (e.g., BPH, neuropathic bladder) • Urethra (e.g., stricture)

  24. Acute Renal FailureDiagnostic Tools • Urinary sediment • Urinary indices • Urine volume • Urine electrolytes • Radiologic studies

  25. Urinary Sediment (1) • Bland • Pre-renal azotemia • Urinary outlet obstruction

  26. Urinary Sediment (2) • RBC casts or dysmorphic RBCs • Acute glomerulonephritis • Small vessel vasculitis

  27. Red Blood Cell Cast

  28. Red Blood Cells Monomorphic Dysmorphic

  29. Dysmorphic Red Blood Cells

  30. Dysmorphic Red Blood Cells

  31. Urinary Sediment (3) • WBC Cells and WBC Casts • Acute interstitial nephritis • Acute pyelonephritis

  32. White Blood Cells

  33. White Blood Cell Cast

  34. Urinary Sediment (4) • RTE cells, RTE cell casts, pigmented granular (“muddy brown”) casts • Acute tubular necrosis

  35. Renal Tubular Epithelial Cell Cast

  36. Pigmented Granular Casts

  37. Acute Renal FailureUrine Volume (1) • Anuria (< 100 ml/24h) • Acute bilateral arterial or venous occlusion • Bilateral cortical necrosis • Acute necrotizing glomerulonephritis • Obstruction (complete) • ATN (very rare)

  38. Acute Renal FailureUrine Volume (2) • Oliguria (100-500 ml/24h) • Pre-renal azotemia • ATN • Non-Oliguria (> 500 ml/24h) • ATN • Obstruction (partial)

  39. Acute Tubular NecrosisClinical Characteristics

  40. Acute Renal FailureUrinary Indices ATN ATN ATN PR PR 500 40 40 1.0 1.0 20 20 350 PR ATN ATN PR PR UNa (mEq/L) (U/P)Cr UOsm (mOsm/L) FENa RFI

  41. Hydronephrosis

  42. Normal Renal Ultrasound

  43. Hydronephrosis

  44. Hydronephrosis

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