Scintigraphic measurements of canine ileocolonic transit. Direct and indirect effects of eating.

Eight dogs were equipped with ileal catheters, 50 cm proximal to the ileocolonic junction, and serosal electrodes at 5, 25, 55, 100, and 150 cm. Transit was assessed by injecting a bolus of 99mTc-diethylenetriamine pentaacetic acid through the ileal catheter and following isotope movements by serial, 4-min scintiscans. Isotope was injected in separate studies: during phase I of an interdigestive myoelectrical cycle, 10 min before a meal, and or 2 or 4 h after a meal (600 ml, 385 kcal, thickened with 4 g guar). At another time, mouth-to-colon transit of the same meal was measured by labeling it with 111In-diethylenetriamine pentaacetic acid and scanning at hourly intervals for 11 h. Transit of isotope through the terminal ileum and entry into the colon was characteristically erratic; long periods of immobility were interspersed with sudden "bolus" movements. In the fasting studies, most sudden movements occurred while phase III (migrating motor complex) of the interdigestive myoelectrical cycle migrated through the last 50 cm of ileum. Passage of a single migrating motor complex through the terminal ileum propelled about one-half the dose of isotope into the colon; complete clearance of the ileum required two or more migrating motor complexes. Immediately after the meal, ileal movements increased transiently; however, these were followed by a period of quiescence. Overall, the time for 50% of the counts to enter the colon was not different when isotope was injected 10 min before the meal from when the injection was made 2 h postprandially (207 +/- 16 min and 162 +/- 25 min, respectively). However, transit of isotope injected 4 h postprandially was significantly faster (91 +/- 13 min). In the fed state, some bolus movements could be related to specific patterns of ileal motility; however, the majority occurred during apparently random "fed-type" motility. In part II, meal marker accumulated faster in the colon after 3-4 h, suggesting that the rapid ileocecal transit at 4 h postcibal was due to increased flow of chyme through the ileum at this time.