Residual urine, underactive detrusor function, and the nature of detrusor/sphincter dyssynergia

Abstract In a group of 280 patients with mixed pathology the adequacy of the detrusor contraction during voiding has been assessed by a new method. For the group as a whole, residual urine is nearly always the result of the fading away of the detrusor contraction and rarely of premature sphincter contraction. It is strongly associated with failure to attain an adequate detrusor contraction at any time during the micturition. The same is true both for children who show consistent urethral overactivity during voiding and for patients with detrusor/sphincter dyssynergia of neuropathic origin. The results suggest that in detrusor/sphincter dyssynergia or other types of urethral overactivity, it may be misleading to ascribe inefficient bladder emptying solely to the obstructive effect of the urethral closure mechanism; the underactive detrusor function should also be taken into account. Often there appears to be an incomplete activation of the micturition reflex, resulting in both incomplete stimulation of the detrusor and incomplete relaxation of the urethral closure mechanism.