Approach to Acute Renal Failure

1. Approach to Acute Renal Failure Dr. Mercedeh Kiaii St. Pauls Hospital

2. Acute Renal Failure • Definition: Abrupt decrease in GFR sufficient to result in azotemia • Urine output can be low, normal or high • Anuric: < 100 ml/day • Oliguric: < 400 ml/day • Non-oliguric: > 400 ml/day

3. ARF: Approach • Assess severity and need for acute dialysis • Fluid overload •  k,  HC03 • Uremic encephalopathy • Uremic pericarditis

4. ARF: Approach • R/O chronic or acute on chronic RF • History: • Fatigue, anorexia, nocturia, pruritis, restless legs • Lab: • Anemia,  PO4,  Ca,  iPTH • U/S: • Small (< 8 cm)  Chronic • Normal ( ~9-12)  Acute or Chronic

5. ARF: Approach • Cause of ARF: • Pre-renal • Renal • Post-renal

6. Pre-renal ARF • Decrease in effective circulating volume (ECFV): • True decrease in intravascular volume • Diarrhea, diuretic, hemorrhage etc • Relative decrease in volume • 3rd spacing, poor cardiac output state

7. Pre-renal ARF:Approach • History • P/E • Lab: • Urine Na < 30 • FeNa < 1% (Una X Pcr) / (Pna X Ucr) •  BUN out of proportion to creat • R/O other causes of increase in serum BUN

8. ARF: Post-renal • History: • Change in urine output • Pain • Phx of stones, or BPH, prostate or cervical ca • P/E: • Bladder distension • Prostate enlargement

9. ARF: Post-renal • U/S: Hydronephrosis, hydroureter unless: • Too early • Volume depletion • Retroperitoneal fibrosis • Diuresis renography or urography to rule out nonobstructive urinary tract dilatation

10. ARF: Post-renalEtiology • Intrarenal: • Stones • Papillary necrosis • Tumor, clot • Intratubular: uric acid, calcium oxalate, acyclovir, methotrexate • Extrarenal

11. ARF: Intrinsic renal • Vascular • Main renal artery and intra-renal arteries & arterioles • Glomerular • Interstitial • Tubular

12. ARF: Intrinsic RenalVascular • Urinalysis: Bland • DDx: • Atheroembolic disease, Cholesterol emboli • TTP, PAN • Scleroderma, malignant hypertension • Drugs: • Cyclosporine, tacrolimus • NSAIDS • Cocaine

13. ARF: Intrinsic RenalGlomerular • Nephritic  RBC +/- RBC casts, protein on urinalysis • RPGN • Nephrotic  < 10 RBC (if present), nephrotic range proteinuria ( > 3 g/d) • Mixed (Nephritic / Nephrotic): • MPGN

14. ARF: GlomerularNephritic ( RPGN) RPGN Pauci-immune (IF negative) Immune complex Disease Granular Ig deposition Linear Ig deposition -Wegeners -Microscopic polyarteritis -Churgstraus -Polychondritis -SLE -PIGN -SBE -Anti-GBM -Goodpasteurs

15. ARF: GlomerularNephrotic • Primary: • Membranous, FSGS, MCD • Secondary: • DM, MM, Amyloid • Usually superimposed acute insult in setting of nephrosis  ARF • ATN in MCD • RVT in Membranous • Papillary necrosis in DM • Intratubular obstruction in MM

16. ARF: Interstitial Nephritis • 30% have systemic manifestations • Urinalysis: WBC +/- WBC casts, eosinophils • Etiology: • Drugs: • Abx: penicillins, cephalosporins, sulfonamides, and rifampin • NSAIDS • Diuretics (thiazides, furosemide)

17. ARF: Interstitial Nephritis • Etiology: • Infections: • Pyelonephritis • Systemic infection Immunologic disorders • Sjogrens • Other • Sarcoidosis • Idiopathic

18. ARF: Acute tubular necrosis • Urinalysis: Brown granular casts +/- small amount of protein • Ischemic • Toxic: • Endogenous: • Myoglobin, Hemoglobin, uric acid • Exogenous: • AG, Amphotericin, contrast dye, acyclovir, indinovir

19. ARFCase presentation • 57 y/o male • Phx of CAD with CAGB, gout, borderline hypertension, gastritis • Presented to ER with hx of melena stool for 2 days • No active bleeding in ER, stable • Hgb 60, Creat 295

20. ARFCase Presentation: Approach • Severity of renal insufficiency? • Estimated CrCl: • (140-57)(75 kg) / 295 X 1.2 = 25 ml/min • Determine need for hemodialysis?

21. ARFCase Presentation: Approach • Acute, chronic or acute on chronic? • Hgb not helpful, Po4 & Ca normal • U/S: Normal sized kidneys, symmetric • Etiology of ARF: • Prerenal, renal or postrenal? • Intravascular volume depletion 2ndary to blood loss • EF not known ( hx of cardiac disease) • Recent NSAID use for gout

22. ARFCase Presentation: Approach • Investigations: • Una < 5 • U/S: no hydronephrosis • Urinalysis not available • Diagnosis: • ARF secondary to pre-renal state secondary to blood loss and NSAID use

23. ARFCase Presentation: Approach • Pt d/c’d home and adviced to increase po salt and fluid intake, and avoid NSAIDS, booked for outpt scope, and started on Iron therapy • F/U: • Hgb 68, scope shows H. pylori • Creat 255

24. ARFCase Presentation: Approach • Possible underlying chronic renal disease? • Risk factors: • Hypertension • Gout • Renovascular disease • U/S normal size kidneys in CRF in: • DM, Amyloid, PCKD

25. ARFCase Presentation: Approach • DDx of ARF: • Vascular: ? TTP, ? PAN • Tubular: • Ischemic ATN from volume depletion & hypoperfusion, and intrarenal v/c from NSAIDS • Toxic ATN secondary to uric acid crystals • Interstitial nephritis secondary to NSAIDS • Glomerular

26. ARFCase Presentation: Approach • Urinalysis: • No blood, no WBC, > 5.0 g/l protein • 24 hour urine: 6 g/day protein

27. ARFCase Presentation: Approach • DDx (Nephrotic): • Minimal change disease 2ndary to NSAIDS • Membranous 2ndary to NSAIDS • no known hx of Hep B • FSGS • Systemic causes • ? Multiple myeloma, ? amyloid

28. ARFCase Presentation: Approach • UPEP: Suspicious for monoclonal protein, immunofixation pending • SPEP: Normal

29. ARF:Treatment Strategies • Treat obvious reversible factors: • Pre-renal state, obstruction • Remove possible nephrotoxins • Treat possible RPGN early • Dopamine and mannitol not effective • ANP in oliguric ATN • Urine alkalinization

30. ARF:Treatment Strategies • Avoid other nephrotoxins • Avoid ischemic episodes and volume depletion • Loss of autoregulation • Loss of tubular function

31. ARF:Treatment Strategies • Dialysis therapy: • Daily vs alternate days vs continuous • Bio-compatible dialyzer membranes