|Classification and external resources|
Oliguria or hypouresis (both names from roots meaning "not enough urine") is the low output of urine. In humans, it is clinically classified as an output more than 80 ml/day but less than 400ml/day. The decreased output of urine may be a sign of dehydration, kidney failure, hypovolemic shock, HHNS hyperosmolar Hyperglycemic Nonketotic Syndrome, multiple organ dysfunction syndrome, urinary obstruction/urinary retention, DKA, pre-eclampsia, and urinary tract infections, among other conditions.
Beyond oliguria is anuria, which represents an absence of urine, clinically classified as below 80 or 100 ml/day.
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 or 500 mL 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/hour/kg. Alternatively, however, the value of 0.5 mL/kg/h is commonly used to define oliguria in adults as well.
Anuria is clinically defined as less than 50mL urine output per day.
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, diarrhea, 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)
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
Oliguria in infants
Oliguria, when defined as less than 1 mL/kg/h, in infants is not attributed to kidney failure.
- Polyuria (excessive urine production)
- (Anuria) (absolute lack of urine output)
- "oliguria" at Dorland's Medical Dictionary
- Boon et al, Davidson's Principles & Practice of Medicine (20th Ed), p475
- Klahr S, Miller S (1998). "Acute oliguria". N Engl J Med. 338 (10): 671–5. doi:10.1056/NEJM199803053381007. PMID 9486997. Free Full Text.
- Merck manuals > Oliguria Last full review/revision March 2009 by Soumitra R. Eachempati
- Arant B (1987). "Postnatal development of renal function during the first year of life". Pediatr Nephrol. 1 (3): 308–13. doi:10.1007/BF00849229. PMID 3153294.