Oliguria

Oliguria
Other names	Hypouresis
Specialty	Urology

Oliguria or hypouresis is the low output of urine: specifically, more than 80 ml/day, but less than 400ml/day. ^[1] 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. ^[1]

The term oliguria is derived from oligo-meaning "small, little," + -uria, from the Greek word ouron, meaning "urine". ^[2]

Definition

Oliguria is defined as a urine output that is less than 1 mL/kg/h in infants, ^[3] less than 0.5 mL/kg/h in children, ^[3] and less than 400 mL ^[3] or 500 mL ^[4] 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. ^[4]

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 ]}

• 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:^{[ 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. ^[5]

See also

• Polyuria (excessive urine production)
• Anuria (absolute lack of urine output)
• Intra-abdominal hypertension (IAH) and Abdominal Compartment Syndrome (ACS)

References

1. Boon, Nicholas A.; et al. (2006). Davidson's Principles & Practice of Medicine (20th ed.). Edinburgh: Elsevier/Churchill Livingstone. p. 475. ISBN   978-0-443-10057-4.
2. "Oliguria | Origin and meaning of oliguria by Online Etymology Dictionary". www.etymonline.com. Retrieved 2020-03-02.
3. Klahr S, Miller S (1998). "Acute oliguria". N Engl J Med. 338 (10): 671–5. doi:10.1056/NEJM199803053381007. PMID   9486997. Free Full Text Archived 2010-05-05 at the Wayback Machine .
4. Merck manuals > Oliguria Last full review/revision March 2009 by Soumitra R. Eachempati
5. 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. S2CID   9166918.