Air cystometrography and sphincter electromyography in patients with bladder outlet obstruction.

38 patients with infravesical obstruction secondary to benign prostatic hypertrophy had CO2 cystometrography (CMG) and sphincter electromyography (EMG) at onset of retension and 6 weeks after intermittent bladder drainage. Neurological diseases were excluded in these patients. Three patterns of CMG tracings were obtained and were called, normal, 'compensating' and 'decompensating' on the basis of the volume: pressure ratio of the curves. By strict definition, no abnormal detrusor contractions were seen in any of these patients who also all had normal sphincter electromyography. It is questionable therefore if infravesical obstruction, in the absence of neurological deficits can account for the uninhibited detrusor contractions described in the literature. Rather it is possible to explain the above CMG tracings on the effects of obstruction on the bladder smooth muscle and collagen fibers which have been shown to be non-neural dependent.