Oliguria or hypouresis is the low output of urine specifically 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.
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.
Olig- (or oligo-) is a Greek prefix meaning small or few.
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
- Polyuria (excessive urine production)
- Anuria (absolute lack of urine output)
- Intraabdonmial hypertension (IAH) and Abdominal Compartment Syndrome (ACS)
- Boon et al, Davidson's Principles & Practice of Medicine (20th Ed), p475
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- "Archived copy". Archived from the original on 2008-09-14. Retrieved 2009-01-19.CS1 maint: Archived copy as title (link)
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