Bladder instability. Is the primary defect in the urethra?

The urethral response to bladder filling has been studied by synchronous measurement of four points in the proximal urethra and bladder using microtip transducers. Twelve male patients with urodynamically proven bladder instability had falls in urethral closure pressure of 30 cm of water 3 s before the unstable detrusor contraction. There was a lack of awareness of the urethral relaxation, the sensation of urgency occurring only when the detrusor contracted. The suggestion is made that the sequence of events occurring in these patients with bladder instability is fundamentally no different from a normal voiding sequence and that it may be more appropriate to re-educate the muscles of the proximal urethra than to treat the detrusor instability.