Definition/Key Clinical Features
Differential Diagnosis
Best Tests
Best Therapy
Best References

Definition/Key Clinical Features

• An abrupt decrease in renal function occurring over hours to days sufficient to result in retention of nitrogenous waste
• Usual criteria are as follows:
  • Increase in serum creatinine of 0.5 mg/dl or
  • 25% increase in serum creatinine or
  • 25% decrease in glomerular filtration rate (GFR)
• Epidemiology
  • Incidence: 1% of hospital admissions
  • Affects 2% to 5% during hospitalization
  • Affects up to 20% of patients in intensive care units
  • Occurs in 4% to 15% of patients after cardiovascular surgery
• Prognosis
  • Mortality: 50% to 80% in acute renal failure (ARF) associated with sepsis, hypotension, and respiratory failure
  • Complete recovery of renal function in most survivors
  • Small percentage of patients with acute tubular necrosis (ATN) may require long-term dialysis
• Clinical manifestations
  • Fatigue
  • Weakness
  • Nausea
  • Vomiting
  • Loss of appetite
  • Metallic taste in mouth
  • Itching
  • Confusion
  • Fluid retention
  • Hypertension

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Differential Diagnosis

• Prerenal azotemia
  • Absolute decrease in effective blood volume
  • Relative decrease in blood volume (ineffective arterial volume)
  • Arterial occlusion
• Renal azotemia
  • Vascular causes
  • Acute glomerulonephritis
  • Acute interstitial nephritis
  • Acute tubular necrosis
    • Ischemia
    • Sepsis syndrome
    • Nephrotoxicity
      • Exogenous nephrotoxins
      • Endogenous nephrotoxins
• Postrenal azotemia (obstruction of collecting system)

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Best Tests

• History
  • Previous renal function
  • Nephrotoxins
    • Medications
      • NSAIDs
      • Aminoglycosides
      • Amphotericin B
      • Cisplatin
      • Angiotensin-converting enzyme inhibitors (in volume-depleted patients)
    • Radiocontrast agent
    • Ethylene glycol
    • Rhabdomyolysis
    • Hyperuricemia (tumor lysis syndrome)
    • Hepatorenal syndrome
  • Surgery
    • Type and duration
    • Hemodynamics
    • Blood loss
    • Anesthetic used
  • Infection or sepsis
• Physical examination
  • Fever
  • Volume status
    • Orthostatic hypotension
    • Edema
    • Jugular venous distention
    • Crackles
    • S₃ gallop
  • Skin
    • Diffuse rash (drug reaction)
    • Livedo reticularis
    • Atheroemboli
  • Bladder
    • Suprapubic fullness
    • Bladder catheterization to assess postvoid residual volume and to relieve bladder obstruction
• Laboratory studies
  • Blood urea nitrogen (BUN)
  • Serum creatinine
  • Electrolytes
  • Urinary volume
  • Urinalysis and urine sediment
  • Urinary indices
    • Used to differentiate between prerenal azotemia and ATN
    • Urinary sodium: prerenal azotemia, < 20; ATN, > 40
    • Urine osmolarity: prerenal azotemia, > 500; ATN, < 450
    • Fractional excretion of sodium: prerenal azotemia, < 1%; ATN, > 1%
    • BUN-to-creatinine ratio: prerenal azotemia, > 20:1; ATN, NA
    • Urine creatinine–to–plasma creatinine ratio: prerenal azotemia, > 40; ATN, < 20
• Imaging studies
  • Indications
    • Diagnosis uncertain, clinical situation suggests other possibilities (e.g., obstruction, vascular accident)
    • Clinical findings make diagnosis of prerenal azotemia or ATN less likely
    • Oliguria persists > 4 wk
  • Renal ultrasonography
    • Initial imaging procedure of choice
  • High-resolution CT
    • Test of choice for suspected urinary tract calculi
  • Radionuclide methods
    • Assessing renal blood flow and excretory function
  • Magnetic resonance angiography
    • Evaluation of renal arterial or venous thrombosis or obstruction

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Best Therapy

• Identify patients with risk factors
  • Advanced age
  • Abnormal renal function or diabetes
  • Volume depletion
  • Recent vascular surgery
  • Recent trauma
• Avoid nephrotoxic agents
• Apply preventive strategies in specific circumstances
  • Use of contrast media
    • Hydration with normal saline 1 ml/kg/hr 8–12 hr before and 8–12 hr after procedure
    • Limit volume of contrast used
    • Iso-osmolar contrast for high-risk patients
    • Acetylcysteine, 600 mg p.o., b.i.d., day before and day of procedure
  • Tumor lysis syndrome
    • Hydration and forced diuresis
      • Infuse normal saline to maintain urine output 3–5 L/day
    • Urinary alkalization
      • Infuse 100–150 mEq sodium bicarbonate to maintain urine pH > 7
      • Infuse acetazolamide 1 g/m²
      • Avoid significant metabolic alkalosis
    • Allopurinol, 300–600 mg/day, starting 3 days before chemotherapy; adjust dose for renal impairment
• Rhabdomyolysis
  • Hydration
    • Infuse normal saline to replace any volume depletion, then infuse at 200–300 ml/hr and follow hemodynamic status
  • Pharmacologic treatment
    • Mannitol (25 g/100 ml) + sodium bicarbonate (100 mEq/100 ml) + 800 ml 5% dextrose in water
    • Infuse at 250 ml/hr
    • Monitor fluid intake, urine output, basic metabolic panel
    • If urine output good, continue infusion until myoglobinuria resolves
    • If patient oliguric (urine output < 400 ml/24 hr), stop infusion, manage as established renal failure
  • Surgical procedures
    • Recognize patients with high-risk conditions
    • Avoid volume depletion
    • Avoid hypotension
    • Avoid nephrotoxic agents

• Emergent intervention
  • Severe hyperkalemia
  • Marked fluid overload with pericardial tamponade
  • Extreme metabolic acidosis
• Dialysis
  • Severe hyperkalemia, acidosis not easily controlled by medical treatment, or both
  • Fluid overload not responsive to fluid restriction, diuretics, or both
  • Signs or symptoms of uremia (e.g., pericardial friction rub, asterixis, mental status changes, seizure)
• Supportive therapy
  • Nutritional support in patients with ATN
• Treatment of complications
  • Volume overload
  • Hyponatremia
  • Hyperkalemia
  • Acidosis
  • Calcium and phosphate imbalances
  • Anemia

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Best References

Blantz RC: Kidney Int 53:512, 1998 [PMID 9461116]

Brivet FG, et al: Crit Care Med 24:192, 1996 [PMID 8605788]

Kandzari DE, et al: Am J Cardiovasc Drugs 3:395, 2003 [PMID 14728060]

Sheridan AM, et al: Curr Opin Nephrol Hypertens 9:427, 2000 [PMID 10926180]

October 2006