Characteristics of the urethral pressure profile in flaccid male paraplegics

Several aspects of urethral function were studied in an attempt to identify the factors causing urinary retention in the flaccid paraplegic patient. The urethral pressure was much higher in all patients at the external sphincter than at the bladder neck. In patients studied sequentially, even from very early following injury, there was little variation in the maximum urethral closure pressure. Radiological studies showed the point of maximal resistance to be distal to the verumontanum. The urethral pressure at this point was largely abolished by phentolamine infusion. There was no variation in the activity of this region with bladder filling or postural change. It is concluded that in flaccid male paraplegics the major component of urethral resistance is constant, adrenergically innervated muscular resistance in the external sphincter region.