Acute urinary retention--a urodynamic assessment.

Thirty male patients with acute urinary retention were studied by standard urodynamic techniques on admission to hospital. Ten individuals also underwent cystography and sequential urodynamic testing over 96 h. Twenty-three per cent of patients did not require subsequent prostatectomy. Inability to initiate a voiding contraction during cystometry at the time of admission was associated with a prolonged duration of retention and a greater retained volume. The internal urethral meatus is closed in retention, and release of the retention results in an increase in profile length and maximum urethral closure pressure and a decrease in maximum urethral pressure. Free catheter drainage was associated with a reduction in bladder capacity and the appearance of detrusor instability.