Rectal compliance and rectal sensation in constipated adolescents, recovered adolescents and healthy volunteers

Objectives: A subgroup of children with functional constipation (FC) are unresponsive to conventional treatment. Abnormal rectal function due to increased distensibility (compliance) might be an underlying mechanism of therapy-resistant FC. It is hypothesised that rectal compliance is normal in patients who are successfully recovered from FC (RC). Methods: Using a barostat, a pressure-controlled intermittent distension protocol was performed in FC patients, RC subjects free of symptoms for at least 4 years and healthy volunteers (HVs). Rectal compliance was calculated using a non-linear mixed-effect model for volume-pressure curves. Results: Forty- seven FC patients, median (range) age of 12 (11-17) years, and 20 RC subjects, 15 (11-18) years, were studied and compared with 22 HVs, 14 (8-16) years. The median (5th-95th percentile) rectal compliance in HVs was 16 (12-20) ml/mm Hg.FC patients had a median rectal compliance of 25 (13-47) ml/mm Hg and RC subjects 20 (12-35) ml/mm Hg, which was significantly higher compared with HVs (p, 0.001 and p = 0.003). RC subjects had lower rectal compliance when compared with FC patients (p = 0.02). Forty- five percent of RC subjects had a rectal compliance above the upper limit of normal (> 95th percentile of HVs), which was significantly less compared with 75% of FC patients (p = 0.02). Conclusion: While rectal compliance in RC subjects is lower when compared with adolescents with FC, almost half of the RC subjects showed an increased rectal compliance. The role of rectal compliance in therapy-resistant FC seems limited, because recovery is possible despite an increased rectal compliance.