Oliguria

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, per 24h in adults - this equals 17 or 21 mL/hour. For example, in an adult weighing 70 kg it equals 0.24 or 0.3 mL/kg/h. Alternatively, however, the value of 0.5 mL/kg/h is commonly used to define oliguria in adults as well. ==Diagnostic approach==

Perform ultrasound examination of the kidney to rule out obstructive processes. The mechanisms causing oliguria can be categorized globally in three different categories: • Prerenal: in response to hypoperfusion of the kidney (e.g. as a result of dehydration by poor oral intake, cardiogenic shock, diarrhoea, G6PD deficiency, massive bleeding or sepsis) • Renal: due to kidney damage (severe hypoperfusion, rhabdomyolysis, medication) • Postrenal: as a consequence of obstruction of the urine flow (e.g. enlarged prostate, tumour compression urinary outflow, expanding hematoma or fluid collection) Postoperative oliguria Patients usually have a decrease in urine output after a major operation that may be a normal physiological response to: • fluid/ blood loss – decreased glomerular filtration rate secondary to hypovolemia and/or hypotension • response of adrenal cortex to stress-increase in aldosterone (Na and water retention) and antidiuretic hormone (ADH) release ==Babies==

Oliguria, when defined as less than 1 mL/kg/h, in infants is not attributed to kidney failure. ==See also==