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Acute Renal Failure

Acute Renal Failure

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Acute Renal Failure

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  1. Acute Renal Failure Adopted from: Malcolm Cox, M.D.

  2. Acute Renal FailureDefinition • characterized by a rapid decline in glomerular filtration rate (GFR) over hours to days • 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 Failure • Rapid decline in the GFR over days to weeks. • Cr increases by >0.5 mg/dL • GFR <10mL/min, or <25% of normal Acute Renal Insufficiency • Deterioration over days-wks • GFR 10-20 mL/min

  5. Definitions AnuriaNo UOP Oliguria: UOP<400-500 mL/d Azotemia: Incr Cr, BUN • May be prerenal, renal, postrenal • Does not require any clinical findings Chronic Renal Insufficiency • Deterioration over mos-yrs • GFR 10-20 mL/min, or 20-50% of normal ESRD = GFR <5% of nl :

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

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

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

  9. Review Raff Reff PGC RAP

  10. 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

  11. Acute Tubular NecrosisClassification • Ischemic • Nephrotoxic

  12. Acute Tubular Necrosis

  13. Acute Tubular Necrosis

  14. 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)

  15. Acute Tubular Necrosis

  16. Acute Tubular Necrosis

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

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

  19. Acute Interstitial Nephritis

  20. Cholesterol Embolization

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

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

  23. 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

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

  25. 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)

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

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

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

  29. Red Blood Cell Cast

  30. Red Blood Cells Monomorphic Dysmorphic

  31. Dysmorphic Red Blood Cells

  32. Dysmorphic Red Blood Cells

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

  34. White Blood Cells

  35. White Blood Cell Cast

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

  37. Renal Tubular Epithelial Cell Cast

  38. Pigmented Granular Casts

  39. 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)

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

  41. Hydronephrosis

  42. Normal Renal Ultrasound

  43. Hydronephrosis

  44. Hydronephrosis