Sympathetic dyssynergia in the region of the external sphincter: a possible source of lower urinary tract obstruction.

Voiding cystourethrography demonstrated urethral constriction at the level of the external urinary sphincter in 10 patients with neurological dysfunctions. Ten mg. phentolamine mesylate intravenously alleviated this constriction, permitting better flow and reducing residual urine in 5 patients with a traumatic spinal injury, 2 with transverse myelitis and 1 who had had a cerebrovascular accident. Oral therapy with phenoxybenzamine hydrochloride, used in 7 of the 8 patients, reduced the post-void residual urine and produced improvement in hydronephrosis when present. These observations are consistent with the presence of a significant sympathetic component to obstruction at the region of the external sphincter in certain neurological disorders.