Role of the ileocecal junction in the motor response to intestinal resection

Abstract

Extensive resections of the distal small intestine are associated with motor disruption in the proximal remnant. Luminal contents such as bacteria and short-chain fatty acids may play a role. We evaluated the effect of bypass of the ileocecal junction (ICJ) on the motor response to a 50% distal resection. Thirty-five dogs were divided into three groups: transection control (TC, n = 11); 50% distal resection with intact ICJ (DR, n = 12), and 50% distal resection with jejunocolostomy to bypass the ICJ (DRBP, n = 12). Motor activity, intestinal transit, nutrition, absorption, and motor active hormones were studied over a 3-month period. Caloric intake was reduced and nutritional status similarly impaired in both resected groups. Steatorrhea, however, was significantly greater after DRBP. Intestinal structural adaptation was similar in both resected groups at 12 weeks. Animals in the bypass group demonstrated elevated intraluminal short-chain fatty acid and anaerobic bacterial counts. Migrating motor complex frequency was similar in the three groups; distal starts, however, were more frequent in both resected groups. Clustered contractile activity was prominent in the remnant after both DR and DRBP (50% and 32% recording time occupied by clusters, respectively [not significant]). Basal levels of peptide YY were increased following resection and this increase was unaffected by ICJ bypass. Postprandial neurotensin concentrations were transiently increased after distal bowel resection. In contrast, the postprandial neurotensin response was abolished following resection with bypass of the ICJ. Basal motilin levels were reduced following resection alone but not after resection with ICJ bypass. The motor response to resection does not appear to be related to alterations in circulating levels of hormones localized to the distal ileum; neither does it seem to be influenced by luminal bacteria and short-chain fatty acids or retention of a sphincteric mechanism at the ICJ. These findings also raise questions about the role of short-chain fatty acids and bacteria in the generation of the various distinctive motor patterns of the distal ileum. Resection of the distal ileum through loss of the receptor site for either retarding reflexes or bile salt absorption may be of greater importance in determining the motor response to resection.