The inability to urinate (retention) is frequently caused by injury, infection, or medications. You may urinate less when you are dehydrated.

Retention occurs more frequently in men than in women and is often caused by prostate enlargement. Prostate enlargement develops gradually; early symptoms include urinating in a small stream (incomplete retention) and difficulty starting urination.

In both women and men, the inability to urinate occurs occasionally after surgery or when there is a blockage of the urethra. Problems with the structure or function of the urinary tract, such as vesicoureteral reflux or an obstruction in the urinary tract (a blood clot or bladder stone, for example) can also cause retention.

The inability to urinate may also be a symptom of a serious problem, such as acute renal failure.

How quickly the inability to urinate develops may help determine the seriousness of the symptom. Call your health professional if you are unable to urinate.