Crucial Role of Rectoanal Inhibitory Reflex in Emptying Function After Anoplasty in Infants with Anorectal Malformations

Constipation is a common problem after reconstructive surgery for anorectal malformations. The underlying pathophysiology of the constipation in these patients is unclear. The objective of this study was to compare manometric disturbance in infants with and without post-anoplasty constipation. Anorectal manometry studies were performed within 12 months of anoplasty, as a part of the follow-up protocol, in 24 infants aged less than 3 years who had anorectal malformations. The manometric profiles studied were mean resting anal pressure (ArP), mean resting rectal pressure (RrP), mean resting rectoanal pressure gradient (RRPG), peak squeeze pressure (PSP), and the presence of the rectoanal inhibitory reflex (RAIR). Eight of 24 infants (33%) experienced constipation during the examination period. There was no difference in pressure profiles between low and non-low anomalies. In the non-constipation group, RrP was 5.1 mmHg, ArP was 21.0 mmHg, RRPG was 16.0 mmHg, and PSP was 88.4 mmHg. In the constipation group, RrP was 7.3 mmHg (p = 0.37), ArP was 37.5 mmHg (p = 0.03), RRPG was 3.05 mmHg (p = 0.05), and PSP was 81.7 mmHg (p = 0.77). RAIR was present in 93.75% of cases without constipation and 12.5% of cases with constipation (p < 0.01). One patient who had clinical conversion from constipation to a good result also showed positive conversion of the RAIR. RAIR and anal resting tone play important roles in emptying function. As far as possible, these functions should be preserved during reconstruction