Studies on the Defecation Reflex in Man

Abstract

In patients with cecostomies and in patients with urinary bladder substitutes obtained from either the sigmoid colon or the cecum, the motor activity in different parts of the large bowel was recorded with the aid of open tip tubes and a pressure-recording apparatus after administration of a contact laxative (Dulcolax®). Administration of Dulcolax® into the cecum of patients with cecostomy produced motor activity locally as well as in the transverse colon and in the sigmoid. When the drug was administered into the cecum of patients with isolated cecal bladder replacements, motor activity was recorded in the cecum but not in the sigmoid. Rectal application of Dulcolax® initiated motor activity in the intact sigmoid as well as in the isolated sigmoid bladder substitute but not in the cecum in patients with cecostomies nor in the cecal bladder replacements. The experiments indicate that only the left colon is engaged in the defecation mechanism elicited by rectal stimulation. The motor response in the left colon after rectal stimulation is mediated by a reflex with its afferent limb from the rectal ampulla. The motor response in the sigmoid after cecal stimulation is elicited by impulses mediated by intrinsic nervous pathways in the intestinal wall.

Key-words:

• Cecostomies
• defecation reflex
• motor activity
• urinary bladder substitutes