Detrusor pressure in bladder outlet obstruction

Synchronous urinary flow and pressure studies were done on 51 male adults consisting of 12 normal subjects and 39 patients with varying degrees of bladder outlet obstruction due to benign prostatic hypertrophy. Mean maximum detrusor pressure levels of 50 mm. Hg and above were found to be indicative of bladder outlet obstruction. Elevated mean maximum detrusor pressure fell preoperatively within normal limits after prostatectomy. Chronic retention of urine was not associated with poor contraction of the detrusor muscle. Clinical findings of obstruction were shown to be inadequate for estimation of maximum detrusor pressure. Recording the detrusor pressure was found to be a better urodynamic test for bladder outlet obstruction than recording the urinary flow rate. Recording urinary flow is, however, a simple test and should remain a screening test for impaired drainage of the bladder outlet.