Paradoxical sphincter reaction and associated colorectal disorders.

Of 71 patients with paradoxical sphincter reaction, 54 had symptoms of constipation or outlet obstruction and 17 were incontinent. The patients were investigated with defecography, colon transit time, anorectal manometry and electromyography. Ninety-six percent of the patients had additional changes in anorectal anatomy and physiology; 70% of the patients had abnormal defecography and 42% had delayed colon transit time. Decreased maximal anal pressure (MAP) and maximal squeeze pressure (MSP), indicating impaired function of the anal sphincters might be one reason for incontinence in patients with paradoxical sphincter reaction. The paradoxical reaction occurred in the puborectalis muscle and in three tested sites in the external sphincter. It is sufficient to record the EMG activity in one muscle and at one point to diagnose a paradoxical sphincter reaction. The absence of a normal closing reflex on electromyography is evidence for a paradoxical sphincter reaction. Denervation was more pronounced in the external sphincter than in the puborectalis muscle. The right pudendal nerve was subjected to damage more often than the left nerve.