Morphological aspects of surgical treatment for anal achalasia in children

BACKGROUND: The primary clinical manifestations of anal achalasia include constipation and, in advanced cases, overflow incontinence, which require differentiation from other conditions. Differential diagnosis between these conditions often depends solely on the histological examination results of the internal anal sphincter, which are insufficiently covered in the literature. Treatment options for pediatric anal achalasia include botulinum toxin injections, although sphincterotomy remains the most effective method. However, factors determining the efficacy of internal sphincterotomy, particularly related to histological features, remain poorly understood. AIM: To analyze surgical outcomes and assess the condition of the ganglionic cells of the anal canal and rectum in children with anal achalasia. MATERIALS AND METHODS: The study included 64 pediatric patients who underwent internal sphincterotomy involving excision and histological examination of a 4 cm × 1 cm segment of the underlying muscular layer (Lynn’s procedure). RESULTS: Positive clinical outcomes, characterized by daily bowel movements and resolution of overflow incontinence, were achieved in 39 patients. Conversely, 25 patients showed persistent constipation and/or overflow incontinence postoperatively. Histological examination revealed a significant increase in connective tissue within the internal anal sphincter. However, in patients with and without a positive outcome after internal sphincterotomy, the total number of neurons and interneurons at +3 cm and +5 cm from the anus was approximately the same. Rectal dilation persisted in 100% of patients with unsuccessful outcomes, whereas a reduction in previously dilated rectal diameter was noted among patients with successful outcomes. CONCLUSIONS: Anal achalasia is characterized by at least a threefold reduction in neuron count within the internal anal sphincter compared to normal. However, surgical outcomes were independent of the total number of neurons and interneurons. A nonlinear relationship in the number of ganglion cells was identified in the resected segments of the internal sphincter muscle, with an increasing density from the distal to the proximal part. Persistent rectal dilation following Lynn’s procedure was inversely correlated with treatment efficacy in patients with anal achalasia who did not achieve a positive outcome.