Effects on Anorectal Function of Endoscopic Submucosal Dissection for Rectal Tumors Involving the Dentate Line

Objective: Endoscopic submucosal dissection (ESD) is a specific procedure that uses an electrosurgical knife for en-bloc resectioning large tumors. However, no study has examined the effect of ESD on the defecation function of patients with rectal tumors. We aimed to investigate the potential effects caused by ESD by analyzing changes in the morphology and movement of the anorectum pre- and post-ESD. Methods: This prospective observational study included 11 patients with anorectal tumors who underwent ESD between April 2020 and February 2022. Pre-ESD assessments included anorectal manometry and defecography. Post-ESD assessments were conducted 2 months later, including anorectal manometry, defecography, and proctoscopy for ulcer and stenosis evaluation. Results: The median patient age was 73 years, including seven males and four females. Eight patients (73%) had a tumor in the lower rectum, and the extent of resection was less than 50% of the rectal lumen. Resection reached the dentate line in six cases (55%). In the patients with post-ESD mucosal defects involving the dentate line, the median of functional anal canal length significantly decreased from (3.4 cm pre-ESD to 2.8 cm post-ESD, p = 0.04). Defecography revealed one case with incomplete evacuation (<50%) and incontinence post-ESD. Interestingly, patients with pre-existing rectoceles noted resolution of lesions post-ESD. None of the patients reported daily constipation or fecal incontinence. Conclusions: While rectal ESD is unlikely to cause significant real-world defecation difficulties, alterations in rectal and anal canal morphology and function may occur if the dentate line is involved in the resection range.