PP-13 FATIGUE RATE INDEX IS HIGHER IN CHILDREN WITH FUNCTIONAL CONSTIPATION AND RETENTIVE FECAL INCONTINENCE.

The fatigue rate index (FRI) is a parameter in anorectal manometry (ARM) to assess sustained voluntary contraction, considering the squeeze pressure and fatigability of the external anal sphincter. It is used in adults to detect fecal incontinence even in patients who present normal squeeze pressures. The FRI in adult patients with functional constipation is similar to controls.The aim of this preliminary study was to evaluate the feasibility and values of FRI in children with retentive fecal incontinence secondary to functional constipation.This retrospective study evaluated 105 ARM performed from Jan 2014 to Apr 2015. 42 patients were selected (were able to perform a voluntary contraction and had no co-morbidities other than functional constipation). 14 of those (33,3%) collaborated in sustaining contraction for 40 seconds (s), allowing the evaluation of the FRI. Patients with retentive fecal incontinence secondary to functional constipation (n = 7, aged 6 to 13 years, 6 boys) were our interest group. Patients with functional constipation without fecal incontinence (n = 7, aged 6 to 13 years, 4 boys) were considered a reference group. The ARM were performed with a radial eight-channel perfusion catheter (Dynamed™, Sao Paulo, Brazil) and the FRI was calculated (Proctomaster 6.4) in the first 20 s and overall 40 s of sustained voluntary contraction.In the first 20 s of contraction, the fecal incontinence group showed a significantly higher mean FRI (2.48 ± 1.39 min) compared to the reference group (1.13 ± 0.72 min, p = 0.042), which was not observed in the 40 s due to less uniform contraction. The anal resting pressure was higher in fecal incontinence group (76.83 mmHg) than in the reference group (54.13 mmHg), but the statistical study did not reach significance (p = 0.051).The mean FRI obtained in this study is lower than the reported in constipated adults (2,8 min).We hypothesized that the higher FRI found in children with retentive fecal incontinence may be associated with retention behavior in cases of severe constipation and to higher anal resting pressure in patients with retentive incontinence.FRI may be feasible in older children, its reference value may be lower than in adults and it is higher among patients with retentive incontinence.