First Things First (assess & treat for the following)

• Is there an acute increase in BUN or serum creatinine?
• Is pt oliguric (100-500 mL/d), anuric (< 100 mL/d) or polyuric (>500 mL/d)?
  • If anuric, think complete urinary tract obstruction, bilateral renal arterial or venous occlusion, bilateral cortical necrosis, overwhelming acute tubular necrosis (ATN) or glomerular nephritis (GN).
  • If polyuric, think recovery phase ATN, interstitial nephritis, partial intermittent obstruction, postobstructive renal failure (RF).
• Place bladder catheter to rule out or relieve lower urinary tract obstruction.
• Collect urine sample for analysis, lytes & creatinine prior to interventions (eg, diuretics).
• Assess & correct volume status & electrolyte abnormalities.
• Avoid further renal insult such as hypovolemia, hypotension, nephrotoxins.
• Adjust dosages of all renally excreted drugs.
• Identify & aggressively treat potentially reversible causes of RF.
• Is it prerenal, renal or postrenal?
  • Prerenal
    • Hypovolemia (GI, renal, skin losses, hemorrhage, third-spacing)
    • Decreased effective intravascular volume (hypoalbuminemia, cirrhosis, nephrotic syndrome, left ventricular cardiac failure, vasodilator therapy, anesthetics, anaphylaxis, sepsis)
    • Renal artery occlusion
    • Autoregulatory failure in states of renal hypoperfusion, due to NSAIDs, ACE inhibitors
  • Renal
    • Glomerular/vascular
      • Acute GN (Goodpasture’s, SLE, Henoch-Schonlein, poststreptococcal)
      • Vasculitis/immune complex disorders: hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP), polyarteritis nodosa (PAN), Wegener’s granulomatosis
      • Malignant HTN
      • Bilateral renal vein thrombosis
    • Acute interstitial nephritis (AIN)
      • Ischemia
      • Toxins (eg, aminoglycosides, cyclosporine, myoglobin)
    • AIN
      • Drug hypersensitivity
      • Infections
      • Immunologic disorders
  • Postrenal
    • Extrarenal
      • Ureteral obstruction (bilateral or solitary kidney)
      • Lower tract obstruction (bladder neck or urethra)
    • Intrarenal: tubular occlusion (eg, crystals, protein, pyogenic debris, stones, blood clots, papillary necrosis)