[Sphincter function following colo-anal anastomosis]

Physiology of ileal pouch-anal anastomosis. Current concepts

PURPOSE

Increasing experience with ileal pouch-anal anastomosis (IPAA) associated with increasing knowledge about anorectal physiology has lead to a large number of publications. The purpose of this review is to evaluate the current understanding of fecal continence as revealed by the evolution of the ileoanal procedure.

METHODS

Review of the literature covering the most important physiologic parameters involved in fecal continence was undertaken.

RESULTS

Rectoanal inhibitory reflex is probably absent after IPAA but is preserved when distal anorectal mucosa is spared. Anal resting pressure decreases but is less affected when the internal anal sphincter is less traumatized. Squeeze pressure is not importantly affected, and the importance of reservoir function as a determinant of stool frequency is emphasized. IPAA does not affect the coordination between pouch and anal canal motility in the majority of cases. Normal continence is preserved, even during the night, by preserving a gradient of pressure between the pouch and anal canal.

CONCLUSIONS

Physiologic concepts are well established, but controversies about the continence mechanism related to IPAA remain. The IPAA procedure has allowed discrimination of details about the function of multiple structures involved in fecal continence.

Intersphincteric resection for low rectal tumours

An abdominoperineal operation is described that extends rectal resection for low tumours into the intersphincteric plane with removal of the internal sphincter. Bowel continuity is restored by coloanal anastomosis. Of 38 patients who underwent surgery since 1984, 34 had low rectal cancer and four carcinoid or large villous adenoma. There was no mortality. Four patients developed local recurrence during a median observation period of 3 years. Continence was satisfactory in all patients. The median daily number of bowel movements during the first months after colostomy closure was 9 but decreased to 3 after 1 year and 1 after 2 years. Anal manometry demonstrated a significant reduction of mean resting pressure from 91.8 to 35.1 cmH2O with no recovery after 2 years (P < 0.0001). Squeeze pressure showed only a transient decrease.

Anorectal function

A review in a historic perspective of the present knowledge of anorectal physiology is presented. The techniques used in the anorectal physiology laboratory are discussed. Application of new sophisticated techniques to anorectal physiology research in recent years continue to improve our knowledge of anorectal function. Anal continence and defecation depend on both the anal sphincter and the rectum. The assessment of patients with functional anorectal diseases should include a more complete physiologic evaluation of the anorectum than used previously.

Relation between electromyography and anal manometry of the external anal sphincter

Thirteen patients with faecal incontinence and 26 control subjects were studied to investigate whether a quantitative electromyographic (EMG) signal could be correlated to anal manometry. Three different electrodes were used--a concentric needle electrode, a disposable sponge electrode, and a hard anal plug electrode. The maximum amplitude of the EMG recording was used as a quantitative parameter. Linear regression showed significant correlation between EMG and anal manometry with the sponge electrode, both at rest and during squeeze. Significant correlation was also found with the concentric needle electrode during squeeze but not at rest. No correlation was found with the hard anal plug electrode either during squeeze or at rest. Reproducibility studies using the sponge electrode showed acceptable day to day variation. In conclusion, quantitative EMG recordings from a disposable sponge electrode placed in the anal canal correlate well to anal manometry and may be used for assessment of sphincter function, but the hard anal plug electrode cannot be recommended.

Results of coloanal anastomosis. A prospective study

Anterior resection with colo-anal anastomosis was carried out in 40 patients. The main indications were rectal neoplasia (30 cases) and irradiation proctitis (8 cases). Early complications occurred in 12 patients and three died of cardiopulmonary complications. Fistula formation and stenosis were the most frequent late complications. In 23 patients with adenocarcinoma operated for cure there was one recurrence. The functional results were good, although it often took up to 1 year until satisfactory continence, stool consistency and frequency were obtained. Manometry showed a significant decrease in anal canal length and resting tone postoperatively. The method is a practicable alternative to total rectal excision.