Usefulness of anorectal myectomy

Abstract

SirWe feel that the conclusions drawn by Pinho, Yoshioka and Keighley (Br JSurg 1989; 76: 1 1 6 3 4 ) are unwarranted. In this study, the authors found that only 17 per cent of patients (I 1/63) with chronic constipation who were treated by anorectal myectomy achieved satisfactory results while as many as 70 per cent (44/63) had outcomes that were poor. Based on these results, and the fact that 10 per cent of their patients (6/63) developed mild incontinence, the authors recommended that anorectal myectomy should no longer be considered in the treatment of patients with chronic constipation.Patients were chosen for myectomy in this study based on videoproctographic and electrophysiologic evidence of 'outlet obstruction'. Selection criteria used included an inability to expel a 100ml balloon from the rectum, increased electrical activity in the puborectalis muscle during attempted defecation, and an inability to open the anorectal angle and evacuate contrast during videoproctography. However, several important factors regarding the patient population selected are unclear. The term 'constipation' is never clearly defined. Since no patient had evidence of megarectum and only 28 patients (44 per cent) had abnormal colonic transit studies, one is uncertain of the true degree of symptoms from which these patients suffered. In addition, only 9 patients (14 per cent) had abnormal rectoanal inhibitory reflexes suggesting internal anal sphincter dysfunction.In reviewing the selection criteria for treating these patients with myectomy, it is not surprising that their overall results were unsatisfactory. This procedure, essentially an extensive internal anal sphincterotomy, has been advocated in the treatment of severe constipation in patients thought to have short segment Hirschsprung's disease. Pinho and associates refer to the favourable results achieved by Martelli et al. ' in the treatment of outlet obstruction, but reviewing this article reveals that Martelli's group performed more than a simple anorectal myectomy. They resected the internal sphincter and additionally included both layers of the rectal musculature posteriorly up to 6 cm above the dentate line.We feel that the selection criteria in this study largely assess the voluntary mechanism of defecation. Since anorectal myectomy only alters the involuntary mechanisms (i.e. the internal sphincter), it would appear that the poor results in this group of patients is quite predictable. Anorectal myectomy is a procedure with merit when it is utilized in the appropriate clinical setting and should continue to be considered in the therapy of a select group of constipated patients with short or ultra-short segment Hirschsprung's disease.