Differences in rectoanal inhibitory reflex duration between patients with refractory functional constipationand myelomeningocele.

Introduction. Usually, during anorectal manometry, only the presence or absence of rectoanal inhibitory reflex (RAIR) is investigated. Studies have reported that a detailed analysis may provide data of interest. Our hypothesis is that RAIR measurement may provide information to detect organic causes (tethered cord, lipoma, etc.) in patients in whom a functional cause had been previously considered. Objectives. To compare RAIR duration in anorectal manometry between patients with refractory functional constipation (RFC) and myelomeningocele (MMC). Population and methods. Observational, analytical, cross-sectional study (2004-2019). Patients with chronic constipation and functional and organic fecal incontinence (myelomeningocele). The anorectal manometry was performed with a water-perfused system, and the duration of RAIR was measured with different volumes (20, 40, and 60 cc). Group 1 (G1): 81 RFC. Group 2 (G2): 54 MMC. Patients with developmental delay, compliant anal sphincter, sacral agenesis and non-cooperative patients were excluded. Results. A total of 135 individuals were included (62 were male). Their median age was 9.57 years in G1 and 9.63 years in G2. Average duration in G1 versus G2 with 20 cc: 8.89 versus 15.21 seconds; 40 cc: 11.41 versus 21.12 seconds; 60 cc: 14.15 versus 26.02 seconds. The difference in RAIR duration with the varying volumes was statistically significant (p = 0.0001). Conclusion. RAIR duration was longer with increasing balloon inflation volumes in both populations. RAIR duration was longer in patients with MMC than in those with RFC. Spinal injury should be ruled out in patients with prolonged RAIR.