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