Comparison of posterior internal anal sphincter myectomy and intrasphincteric botulinum toxin injection for treatment of internal anal sphincter achalasia: a meta-analysis

Internal anal sphincter (IAS) achalasia is a clinical condition with presentation similar to Hirschsprung’s disease, but with the presence of ganglion cells on rectal suction biopsy (RSB). The diagnosis is made by anorectal manometry (ARM), which demonstrates the absence of the rectosphincteric reflex on rectal balloon inflation. The recommended treatment of choice is posterior IAS myectomy. Recently, intrasphincteric botulinum toxin (Botox) injection has been effectively used for treatment of IAS achalasia. The aim of this meta-analysis was to compare the efficacy of posterior IAS myectomy with intrasphincteric Botox injection for treatment of IAS achalasia.

A systematic literature search for relevant articles was conducted using the following databases: MEDLINE ^® , EMBASE^®, ISI Web of Science^SM and the Cochrane Library. A meta-analysis was performed with the studies where IAS achalasia was diagnosed based on the results of ARM and RSB. Odds ratio (OR) with 95 % confidence intervals were calculated.

Sixteen prospective and retrospective studies, published from 1973 to 2009, were identified. A total of 395 patients with IAS achalasia were included in this meta-analysis. Fifty-eight percent of patients underwent IAS myectomy and 42 % Botox injection. Regular bowel movements were significantly more frequent after IAS myectomy (OR 0.53, [95 % CI 0.29–0.99]; p = 0.04). There was no significant difference in continued use of laxatives or rectal enemas (OR 0.92, [95 % CI 0.34–2.53], p = 0.89) and in overall complication rates between both procedures (OR 0.68, [95 % CI 0.38–1.21]; p = 0.19). Looking at specific complications, the rate of transient faecal incontinence was significantly higher after Botox injection (OR 0.07, [95 % CI 0.01–0.54]; p < 0.01). Constipation and soiling were not significantly different between both procedures (OR 0.66, [95 % CI 0.30–1.48]; p = 0.31 and OR 0.24, [95 % CI 0.03–2.07]; p = 0.25). The rate of non-response was significantly higher after Botox injection (OR 0.52, [95 % CI 0.27–0.99]; p = 0.04). Subsequent surgical treatment was significantly more frequent after Botox injection (OR 0.18, [95 % CI 0.07–0.44]; p < 0.0001). Short- and long-term improvements were significantly more frequent after IAS myectomy (OR 0.56, [95 % CI 0.32–0.97]; p = 0.04 and OR 0.25, [95 % CI 0.15–0.41]; p < 0.0001).

This meta-analysis indicates that in patients with IAS achalasia, posterior IAS myectomy appears to be a more effective treatment option compared to intrasphincteric Botox injection. After Botox injection, the rate of transient faecal incontinence, non-response and subsequent surgical procedures were significantly higher compared to IAS myectomy.