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, hyperosmolar hyperglycemic nonketotic syndrome (HHNS), multiple organ dysfunction syndrome, urinary obstruction/urinary retention, diabetic ketoacidosis (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.

The term oliguria is derived from oligo-meaning "small, little," + -uria, from the Greek word ouron, meaning "urine".

Definition

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/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.[citation needed]

The mechanisms causing oliguria can be categorized globally in three different categories:[citation needed]

Postoperative oliguria

Patients usually have a decrease in urine output after a major operation that may be a normal physiological response to:[citation needed]

  • 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

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