Canine ileocolonic sphincter: flow, transit, and motility before and after sphincterotomy
1Digestive Diseases Center, Mayo Clinic and Foundation, Rochester, Minnesota 55905.
Insights
The canine ileocolonic sphincter (ICS) has minimal impact on chyme transit. Integrated motility of the ileum, ICS, and proximal colon is crucial for regulating ileocolonic flow.
Area of Science:
- Gastroenterology
- Comparative Physiology
- Digestive System Motility
Background:
- The ileocolonic junction's regulation is complex, potentially involving integrated motility rather than solely the ileocecal sphincter.
- Previous observations suggested functional motor integration of the ileum, ileocolonic sphincter (ICS), and proximal colon influences ileocolonic junction activity.
Purpose of the Study:
- To test the hypothesis that the canine ileocolonic sphincter (ICS) has a limited regulatory role in chyme transit from the ileum to the colon.
- To investigate the influence of ICS ablation on ileocolonic chyme flow and transit times.
Main Methods:
- Ablation of the canine ileocolonic sphincter (ICS) via extramucosal sphincterotomy in five dogs.
- Measurement of tonic pressures at the ICS before and after surgery.
- Estimation of ileal chyme flow using marker dilution.
- Quantification of ileocolonic flow by total chyme recovery from a colonic cannula.
- Measurement of transit times using nonabsorbable markers after bolus infusion.
Main Results:
- Sphincterotomy significantly reduced tonic pressures at the ICS.
- Ileocolonic sphincterotomy did not significantly alter chyme flow rates or transit times across the ileocolonic junction.
- Ileal motor patterns were observed to change post-sphincterotomy.
Conclusions:
- The ileocolonic sphincter (ICS) appears to exert only a minor influence on chyme transit and flow at the ileocolonic junction.
- These findings underscore the importance of integrated motility patterns among the ileum, ICS, and proximal colon for controlling chyme flow in this region.
Abstract:
Our hypothesis was that the canine ileocolonic sphincter (ICS), per se, would have little regulatory effect on the transit of chyme from ileum to colon. We argued, from earlier observations, that the ileocolonic junction was influenced more by functional motor integration of the ileum, ICS, and proximal colon. In five dogs, the ileocolonic sphincter was ablated by extramucosal sphincterotomy; the operation significantly lowered tonic pressures at the ICS. Animals were then studied in the fasting state and postprandially. Ileal flow was estimated by marker dilution, and ileocolonic flow was estimated by total recovery of chyme from a colonic cannula. Transit times were measured after the bolus infusion of nonabsorbable markers. Ileocolonic sphincterotomy did not significantly alter flow rates or transit times of chyme across the ICS, although ileal motor patterns were changed after sphincterotomy. We concluded that the ICS probably has only a small effect on transit and flow at the ileocolonic junction. These findings argue for the importance of integrated motility of the ileum, ICS, and proximal colon in controlling the flow of chyme in this region.
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