Oliguria is defined as a urine output that is less than 1 mL/kg/h in infants, less than 0.5 mL/kg/h in children, and less than 400 mL daily in adults. It is one of the clinical hallmarks of renal failure and has been used as a criterion for diagnosing and staging acute kidney injury (AKI), previously referred to as acute renal failure. At onset, oliguria is frequently acute. It is often the earliest sign of impaired renal function and poses a diagnostic and management challenge to the clinician. (See Presentation and Workup.)
A standardized definition of AKI has recently been proposed by the Kidney Disease: Improving Global Outcomes (KDIGO) AKI working group, which identifies and stages AKI based on changes in serum creatinine from baseline or a decrease in urine output (oliguria) as shown below.
KDIGO Staging of AKI (Open Table in a new window)
Increase by 1.5-1.9 times baseline within 7 days
Increase by 0.3 mg/dL (26.5 µmol/L) or more within 48 hours
|Less than 0.5 mL/kg/h for 6-12 hours
|Increase by 2-2.9 times baseline
|Less than 0.5 mL/kg/h for 12 hours or longer
Increase by 3 times baseline or greater
Increase to 4 mg/dL (353.6 µmol/L) or greater
Renal replacement therapy initiation
In patients younger than 18 years, decrease in estimated GFR to less than 35 mL/min/1.73m2
Less than 0.3 mL/kg/h for 24 hours or longer
Anuria for 12 hours or longer
Not all cases of acute kidney injury are characterized by oliguria. Renal failure that results from nephrotoxic injury, interstitial nephritis, or neonatal asphyxia is frequently of the nonoliguric type, is related to a less severe renal injury, and has a better prognosis. In addition, the degree of oliguria depends on hydration and the concomitant use of diuretics.
In most clinical situations, acute oliguria is reversible and does not result in intrinsic renal failure. However, identification and timely treatment of reversible causes is crucial because the therapeutic window may be small. (See Prognosis, Presentation, Workup, Treatment, and Medication.)