Sensitivity of the sigmoid colon and rectum in children treated for chronic constipation.

Sensations in the sigmoid and rectum and the response of the anal canal to balloon distension were measured with a latex balloon and pressure transducer in 15 chronically constipated and 15 healthy control children. The constipated children received milk of magnesia and bowel training. Thirteen constipated children were restudied 7-12 months later and 11 were restudied 3 years later. Although thresholds of transient sensation and of the rectosphincteric reflex were not different in constipated and control children, the threshold of fullness, the critical volume, and the volume for constant relaxation were significantly higher in constipated than in control children (p less than 0.05), and remained higher 1 year and 3 years later, even in the children who recovered. The initial data support the concept of a sigmoid and rectum so enlarged that a normal fecal bolus may not cause a sensation of fullness or a sensory stimulus for defecation. Despite improvement in clinical manifestations and normal rectal size, the abnormalities in sensitivity of the sigmoid and rectum persisted in five of eight recovered children. This may explain why these children are so vulnerable to recurrence of constipation and fecal soiling.