Although oliguria is common in patients with AKI, anuria (urine output <50 to 100 mL/day) is rare. Anuria is most often seen in two conditions: shock and complete bilateral urinary tract obstruction.

How does AKI cause decreased urine output?

Post-renal causes of decreased urine output and AKI are those causing physical obstruction of the urinary system distal to the renal pelvis. Obstruction may be internal (e.g. blood clots, urinary catheter debris) or external to the urethra or urinary catheter (e.g. prostatic hypertrophy, urinary catheter kinking).

What causes oliguria?

The most common cause of oliguria is dehydration. Dehydration is when your body doesn’t have enough water or fluids—generally because it’s losing more than it’s taking in. This can happen when you sweat a lot on a hot day or have a stomach bug that causes diarrhea or vomiting.