Effects of Radiation on Intestinal Absorption

Abstract

Profound physiologic and pathologic changes may occur in the gastrointestinal tract following exposure to penetrating radiations, and effects on absorption must be discussed in the light of these changes. Relatively small doses of radiation produce transient but marked changes in gastric emptying time and in gastrointestinal motility. With larger, but sublethal doses, transient effects on the gastrointestinal epithelium are seen in the first few days, resulting from damage to dividing crypt cells. In the lethal range, pathologic changes in the mucosa, secondary to infection and hemorrhage, occur in the second week or later. At supralethal doses, the intestinal villi are denuded completely of epithelium just prior to death on the third to fifth day. Studies within hours of exposure have shown reduced absorption of sugars, fats, electrolytes and other substances, explicable at least partly on the basis of reduced gastric emptying time and intestinal motility. Later decreased absorption of sugars apparently cannot be explained on this basis, and there may be an absorption defect even when apparent regeneration of damaged epithelium has occurred. Absorption of fat may be impaired to a lesser degree. At supralethal doses absorption appears to be affected markedly. Early deaths following large doses of total body radiation and associated with bowel damage appear to be due, at least in part, to a terminal loss of electrolytes and water into and through the denuded intestine. Although active transport and absorption may be impaired or stopped following radiation, the bowel wall appears to constitute an effective barrier to movement (loss) in either direction of nutrients, electrolytes and other substances even with large doses, until complete denudation of epithelium occurs.