Decreased fluid tolerance, accelerated transit, and abnormal motility of the human colon induced by oleic acid.

To determine whether the presence of unabsorbed fat in the colon altered colonic motility, intraluminal pressures were recorded in the terminal ileum and proximal colon, and serial 1-min gamma camera scans were obtained while test solutions labeled with diethylenetetramine pentaacetic acid chelate of indium 111 were infused into the middle portion of the ascending colon. Seven subjects received a control solution, and 6 subjects received an emulsion of oleic acid (4.3 g/100 ml). Oleic acid accelerated colonic transit; isotope accumulated in the rectosigmoid faster in the first 120 min (4343 +/- 1175 cpm) than it did during control infusion (1236 +/- 348 cpm; p less than 0.01). Accelerated transit of oleate was accompanied by high amplitude (greater than 60 mmHg, range 60-95 mmHg), prolonged (greater than 10 s, range 10-48 s), propagated pressure waves; they originated near the ileocecal junction at a median frequency of 1.3 times/hour (mean 4.1, range 0.4-15.7). These were associated with a narrow image of the ascending colon on scintiscan and movement of 65.9% +/- 6.5% of counts from the ascending to transverse colon over the succeeding 4 min. A similar sequence was seen only once in 33 h of infusion with control solutions (p less than 0.01). Associated with these responses, the total volume of infusate tolerated before defecation was less with oleate than with control solutions (311 +/- 21 ml vs. 1049 +/- 71 ml; p less than 0.01). Long-chain fatty acids stimulated unusual motor patterns and reduced the reservoir function of the ascending colon; these effects may contribute to the diarrhea of patients with fat malabsorption.