Internal Anal Sphincter and Late Clinical Outcome in Patients with High Type Anorectal Malformation

The purpose of this study is to investigate the age -related improvement of defecation function in high type anorectal malformation in relation to the assessment of the internal anal sphincter. The function of defecation was studied every 5 years up to 15 years postoperatively according to the Japanese scoring system in our hospital in 50 patients operated for high type (recto-urethral fistula) imperforate anus with posterior sagital anorectoplasty (PSARP) procedure in 25 patients, and 25patients with endorectal pull-through (ERPT). The internal anal sphincter was assessed by anorectal manometry and histology, and the results were analyzed with the clinical outcomes. The defecation scores of the PSARP cases exceeded those of ERPT cases at all age groups, the averaged total score were 7.0 in the PSARP cases vs. 4.6 for ERPT cases at 5 years old, 7.5 vs. 5.2 at 10 years old, and 8.0 vs. 6.7 at 15 years old. The anorectal reflex was seen in 17 of 25 (68%) PSARP cases examined, whereas seen in 5 (20%) of ERPT cases examined. Histologically, the well-developed and thickened internal circular muscle at the rectal end was found only in 40% of the cases, whereas discontinuation and hypoplasty of the muscle were seen in most of the cases examined. The present results indicate that the internal sphincter muscle at the rectal end may be histologically maldeveloped in high type anorectal malformations; however, they can potentially develop after transplanted and contribute to the improvement of passive continence in the late post-operative period.