Small bowel transit of a bran meal residue in humans: sieving of solids from liquids and response to feeding.

Background: Ileal motor patterns are adapted to the propulsion of viscous meal residue, such as bran, which accumulates in the distal ileum postprandially.

Aims: To examine the effects of a second liquid/solid meal on ileal emptying.

Subjects And Methods: Eleven healthy fasting subjects consumed a 1.47 MJ pancake containing 15 g bran and 5 MBq Technetium-99m labelled amberlite resin (meal A). Gastric emptying and transit through the left upper quadrant (proximal) and right lower quadrant (distal) small bowel regions and colon were assessed scintigraphically. Transit was compared with and without a second Indium-111 liquid/solid DTPA labelled 2.28 MJ meal (B) given three hours after the first meal.

Results: Gastric emptying of meal A was slower than meal B (the time for 50% of the activity to leave the stomach (T50) being 113 (11) minutes versus 48 (3) minutes respectively, p < 0.01, n = 11). Both meals passed rapidly through the proximal small bowel (T50 meal A = 57 (14) minutes versus T50 meal B = 42 (11) minutes). Transit of meal A through the distal small bowel was much slower (T50 more than 390 minutes versus 176 (29) minutes for meal B, p < 0.01), resulting in meal B overtaking meal A and entering the colon earlier. Ingestion of the second meal (B) resulted in significantly less meal A marker entering the colon (5 (3)%) at 11 hours than when meal A was taken alone (18 (4)%) (p < 0.05, n = 8).

Conclusions: The distal small bowel selectively retains bran, allowing liquid phase markers through to the colon. Consuming a second liquid/solid meal does not stimulate ileal transit of bran which seems to be propelled quicker by fasting motor patterns.