The relationship between perineal descent and denervation of the puborectalis in continent patients.

It has been suggested that perineal descent causes puborectalis neuropathy. To elucidate this, perineal descent was measured on standard proctograms and prolongation of mean motor unit potential duration was used as the index of denervation of the external sphincter and puborectalis in 9 male and 18 female patients with perineal descent and obstructed defaecation. The findings were compared with 21 normal controls. There was no significant perineal descent below the pubococcygeal line at rest but both males and females had abnormal descent of the anorectal angle on straining and a similar degree of external sphincter neuropathy. Females, however, exhibited a significant degree of puborectalis denervation compared with controls (p less than 0.001) and with male patients (p less than 0.001). Thus external sphincter denervation was associated with perineal descent in both sexes whereas other causes, of which obstetric trauma is a possibility, must be implicated in the puborectalis neuropathy of the females studied.