Is the Afferent Pathway from the Rectum Impaired in Children with Chronic Constipation and Encopresis?

Background & Aims: Rectal sensations to balloon distention are impaired in children with chronic constipation and encopresis. The impairment of rectal sensation, which is often persistent and is related to nonrecovery, could be caused by a defect in the visceral afferent pathways. The aim of this study was to test whether the afferent pathway from the rectum is impaired in children with constipation and encopresis.

Methods: Fifteen healthy children and 15 children with constipation and encopresis were studied. Cerebral evoked potentials (EPs) were studied by averaging results of 100 rectal distentions, which used 10, 20, and 30 mL air. EPs were recorded from Cz' to Fz.

Results: Two different types of EPs were recorded in each control subject and each child with constipation and encopresis. One EP had an early onset and showed multiple positive and negative peaks. The other EP had a much later onset and was triphasic. Early-onset EPs were recorded with significantly smaller distention volumes than the late-onset EPs. N1 and P2 latencies of the early-onset EPs and NI, PI, and NII latencies of the late-onset EPs were significantly prolonged in children with constipation and encopresis compared with controls.

Conclusions: The prolonged latencies suggest a defect in the afferent pathway from the rectum in children with chronic constipation and encopresis.