Function of the anal sphincters in patients with intussusception of the rectum.

Patients with intussusception of the rectum--six with anal incontinence and nine continent--were examined with respect to the function of the anal sphincters. Anal pressure was recorded continuously during rest, during maximal voluntary squeezing of the anal muscles, and during gradual expansion of the rectum by means of a balloon inserted into the rectal ampulla. The maximal anal pressure at rest, which is mainly due to activity of the internal anal sphincter, was lower (P less than 0-001) in the incontinent patients (31 mmHg +/- 5-6) than the continent (67 mmHg +/- 4-3) and the former had significantly smaller relaxations of the internal sphincter upon rectal distension (P less than 0-05). The increase in anal pressure during voluntary squeezing, a function of the external sphincter, did not differ significantly compared with healthy subjects in either incontinent or continent patients. On the basis of the above findings, it is concluded that the function of the internal sphincter is impaired in the incontinent patients.