Assessment of residual urine in men following catheterisation

There is a certain volume of urine left within the bladder which cannot be drained by a catheter. A dilutional method was used to calculate this residual volume in 15 men; 10 had acute retention secondary to benign prostatic hyperplasia and 5 had permanent indwelling catheters for neurogenic urinary incontinence. The mean catheterised residual volume was 98.53 ml for patients with acute retention and 14.48 ml for patients with long-term catheters. The explanation for higher post-catheterisation volumes in the acute retention group is probably multifactorial; bladder sacculation and diverticula, detrusor tone and reflux may all play a role.