Fat absorption from the human gastrointestinal tract in patients undergoing radiation therapy.

Abstract

The effect of ionizing radiation on the gastrointestinal tract was first noted by Walsh in 1897 (1). The circumstances under which the irradiation was given and the amount are unrecorded. Since that time, many studies as to the effect of radiation on the digestive tract have been carried out. These have been directed toward a morbid anatomical evaluation or a physiological evaluation, or both. Excellent studies of the anatomical changes in the small bowel after irradiation in varying amounts may be found in papers by Warren (2, 3), Martin (4), and Senn (5). Their observations have been substantiated by many other workers. The changes have consisted primarily of a loss of the intestinal epithelium, beginning with that in the crypts and progressing to the villi. Ulcerations then appear, extending through the submucosa and sometimes into the serosa. The extent of these lesions and the rapidity with which the process develops depend to a large extent upon the tissue dose received by the area. It has also been found to vary with the experimental animals used (6, 7). The other approach to the study of small bowel damage has been from a functional standpoint. As two of the main functions of the small bowel are motility and absorption, the study may be oriented toward one or both of these. Wallace (8), in 1941, studied a series of our patients undergoing deep x-ray therapy to the pelvis. He found a decreased motility and segmentation of barium in the ileum. He noted also some apparent loss of ileal mucosal pattern on the barium studies. Conard (9) made an extensive study of the motility of the small bowel in rats. He reported a transient increase after irradiation, followed by a generalized slowing with a gradual return to normal on the third or fourth day. Greenfield (10) observed delayed gastric emptying time in rats after irradiation. A second approach to this problem from the physiological aspect is that offered by a study of the absorptive mechanism. Greenfield, working with white rats, described a decrease in the ability of the small bowel to absorb Evans blue dye after irradiation. Buchwald (11) and Moss (12) found a decreased intestinal absorption of carbohydrates, in the form of glucose, mannose, fructose, and arabinose, following irradiation to the exteriorized small bowel in the rat. In 1924 Martin and Rogers (13) described a decrease in fat absorption from the small bowel in irradiated dogs. They carried out their study by staining the intestinal epithelium for fat, after a fatty meal had been administered to the animal. No fat droplets were found within the mucosa, whereas normally they are present in abundance. In 1951 a study of the absorption of fat from the irradiated small bowel of mice was carried out by the use of methyl oleate, with spectrophotometrically active octadecadienoate as a tracer (14). The mice were given 600 to 700 r total body irradiation.