Possible Involvement of Hyperactive Internal Anal Sphincter in Adult Megacolon

Abstract

Background: Adult megacolon comprises a heterogeneous group of conditions. This study is a retrospective review of a series of adult megacolon aimed to discriminate a subpopulation of this condition by elucidating shared physiopathology. Methods: Eight adult megacolon patients without Hirschsprung’s disease were treated over 15 years. Their clinical characteristics were evaluated with an epmphasis on manometric studies. Results: There were three females and five males aged 60.9 years on average. Seven of the eight patients had central nervous system disorders including epilepsy (4), Parkinson’s syndrome (2) and others (5). Three patients had hemorrhoids. All of these eight patients suffered from chronic constipation, and six of them had a history of sigmoid volvulus. Manometric study revealed anal Ultra Slow Waves, a manometric finding representing hyper-active internal anal sphincter, in five patients. Conclusion: Anal ultraslow waves and central nervous disorders were highly prevalent in adult megacolon. Hyperactive internal anal sphincter may be responsible for long standing constipation. Persisting hyperactivity of the internal anal sphincter after surgical treatment is a possible explanation for the recurrence of sigmoid volvulus or megacolon in these patients. More attention should be paid for the physiopathology of the anorectum in adult megacolon.