Variability of motility of the ileum and jejunum in healthy humans

Abstract

Motor patterns of the distal small bowel were defined in healthy humans, using a multilumen polyvinyl tube, passed by mouth in 11 healthy subjects. Five recording sites, spanning 100 cm of tube and featuring a nitrogen hydraulic infusion system, were used to obtain records during 6 h of fasting and 6 or more hours after ingestion of a 600-kcal liquid test meal. The loci of recordings were designated as jejunal, ileal, or terminal ileal, as judged by the length of tube within the intestine and by fluoroscopy. During fasting, the migrating motor complex was present in all subjects and at all levels of the small intestine, but it could not be traced into the colon. Interdigestive cycles were defined primarily by the presence of an “activity front” (phase 3 of the migrating motor complex). Ninety-six migrating motor complexes occurred each 97 min (grand mean for all loci), but intervals between individual activity fronts varied markedly (15–195 min), in contrast to what is reported in other species. The velocity of aboral migration was 4.7 ± 1.8, 1.3 ± 0.4, and 0.9 ± 0.2 cm · min−1 (mean ± SD) in jejunal, ileal, and terminal ileal, respectively. Rates of continuous, rhythmic contractions during activity fronts declined distally: 12.5 to 10.5 (jejunal), 10.9 to 9.3 (ileal), and 10.0 to 8.6 cycle/min (terminal ileal), respectively. In individual subjects, maximum rates of contraction and velocities of migration always declined distally, but the duration of activity fronts was unrelated to the level of recording. Food interrupted the fasting cycles of motility for periods ranging from 2.75 to > 10 h. The transition from the fasting to the fed pattern was prompt and the post-prandial motility was that of irregular bursts of contractions interspersed with transient quiescence. These studies demonstrate that the migrating motor complex occurs throughout the human small intestine, and that inter- and intraindividual variations are marked; food disrupts the complex for variable periods. These variations must be considered when abnormalities are being sought in disease states.