The "plain film" bladder shadow in outflow obstruction: as accurate a discriminant of residual urine as ultrasound.

The height, width and area of the bladder shadow on post-micturition plain abdominal radiography was compared with the residual urine obtained at endoscopy from 58 men presenting with pure bladder outflow obstruction. Each parameter of the bladder shadow correlated significantly with the residual urine in patients in whom this shadow was visible. Post-micturition plain abdominal radiography is considerably cheaper than ultrasound and appears to be equally effective in the determination of residual urine. Its use as the sole imaging technique in the routine management of bladder outflow obstruction is recommended.