The Role of Rectoanal Inhibitory Reflex in the Anal Continence Function

ABSTRACT

PURPOSE: The rectoanal inhibitory reflex (RAIR) aids the anal continence function by a sampling process. On the other hand, it might impair the anal continence function because the internal anal sphincter is relaxed during the reflex. We assessed the parameters of RAIR in incontinent patients with or without a sphincter defect and compared them with healthy control subjects to clarify the exact role of that reflex in the anal continence function. METHODS: The recovery time, slope, amplitude, and area under the reflex curve of the RAIR were measured for 31 normal controls without any history of anorectal surgery (group A), 32 incontinent patients with a sphincter defect (group B), and 49 incontinent patients without a sphincter defect (group C). Incontinence was defined as bowel accidents of more than 3 by the Cleveland Clinic Florida score. A sphincteric defect was defined endoanal sonographically. The mean ages of group A, B, and C were 57.9+/-14.3, 54.5+/-13.6, and 61.8+/-15.4 years, respectively. RESULTS: When group A and group B+C were compared, the recovery times (seconds) were 17.5+/-3.5 and 14.8+/-5.5 (P=.003), the slopes (mmHg/second) were 0.67+/-3.04 and 3.27+/-2.44 (P<.001), the amplitudes (%) were 7.0+/-16.5 and 53.3+/-19.4 (P=.352), and the area under the reflex curve (mmHg*seconds) were 230.2+/-102.15 and 173.0+/-140.8 (P=.020). When group B and group C were compared, the recovery times were 15.0+/-5.8 and 14.7+/-5.3 (P=.828), the slopes were 3.6+/-2.8 and 3.1+/-2.2 (P= .388), the amplitudes were 54.2+/-22.4 and 52.7+/-17.4 (P=.737), and the area under the reflex curve were 188.0+/-151.1 and 163.2+/-134.3 (P=.443). All parameters of the RAIR, except the amplitude were significantly diminished in incontinent patients whether they had a sphincter defect or not. CONSLUSIONS Although the RAIR functions against continence in normal conditions by inhibiting sphincteric tone, it behaves suitably for keeping continence in the presence of incontinence, whatever the cause is, by attenuating the degree of inhibition.