Oliguria

Specialty: Nephrology and urology.

• decrease in urinary volume
• low urinary output
• decreased diuresis

Why it occurs

• Severe dehydration or hypovolemia (due to bleeding, digestive losses or burns, which reduce renal perfusion)
• Acute tubular necrosis (direct ischemic or toxic injury to renal tubular cells)
• Decompensated congestive heart failure (low cardiac output that decreases the glomerular filtration rate)
• Acute glomerulonephritis (glomerular inflammation with collapse of capillary lumens)
• Bilateral obstruction of the urinary tract (postrenal obstructive uropathy due to prostatic hyperplasia, pelvic tumors or bilateral lithiasis)

Initial workup

Immediate determination of serum creatinine, urea nitrogen (BUN) and plasma electrolytes (especially potassium); analysis of the urinary sediment to look for brownish-turbid or bloody granular casts; calculation of sodium ejection fraction (FeNa) and urinary osmolarity to differentiate prerenal origin (FeNa <1%) from intrinsic renal origin (FeNa >2%); urgent renal ultrasound to evaluate the size of the kidneys and rule out hydronephrosis.

Standard management

• Furosemide — loop diuretic, administer 20-40 mg IV only if hypovolemia has been ruled out and there is volume overload evidenced by pulmonary or peripheral edema; avoid in dehydrated patients
• 0.9% saline solution or Lactated Ringer's — intravenous resuscitation fluid therapy if oliguria is of prerenal cause due to dehydration, monitoring hourly diuresis
• 10% calcium gluconate (10-20 ml IV in slow infusion for stabilization of the myocardial membrane if associated with severe hyperkalemia with electrocardiographic changes).