Does the ileocolonic junction differentiate between solids and liquids?

Previous observations from our laboratory have suggested that colonic filling from the ileum is characterised by a series of bolus movements. The present experiments were designed to test the hypothesis that bolus transit of ileal contents into the colon would not distinguish between solids and liquids. After a manometric infusion assembly was positioned by mouth into the ileum of 13 healthy volunteers, a mixture of nutrients (75 kcal), incorporating a solid phase radiolabel (¹¹¹In labelled resin pellets) and a liquid phase marker (^99mTc-DTPA), was infused into the ileum. Transit of both labels from the ileum to colon was quantified scintigraphically and ileal motility was also recorded. When markers were infused into the proximal ileum, 100 cm proximal to the ileocolonic junction (six), there were clear cut examples of discriminant transit, when liquids moved more rapidly from the small to the large bowel than did solids. When isotopes were instilled into the distal ileum, less than 50 cm from the ileocolonic junction, no separate transit of the solid and liquid phases was observed. No specific motor pattern of the ileum was regularly associated with bolus filling of the colon. These results support the hypothesis that the distal ileum can discriminate between solids and liquids but that the ileocecal junction cannot.