Localized subclinical radiation enteropathy prolongs intestinal transit time: An experimental study in a rat model

Intestinal dysmotility is a prominent feature of chronic radiation enteropathy. This study addressed the question whether localized radiation enteropathy without anatomical obstruction influences stomach to cecum transit time. Male rats were orchiectomized and a loop of ileum was sutured to the inside of the scrotum. After 3 weeks postoperative recovery, the “scrotal hernia” containing the transposed intestine was irradiated with 18 twice‐daily fractions of 2.8 Gy, or 9 daily fractions of 5.6 Gy orthovoltage X‐rays. Control animals were operated and sham‐irradiated. Stomach to cecum transit time was assessed 26 weeks after irradiation. A 1‐ml bolus of barium suspension was administered by gavage and diagnostic X‐ray films were obtained at 0,1, 2,2.5, 3, 3.5, and 4 hr. Transit time was defined as the time to the first X‐ray that showed unequivocal contrast filling of the cecum. Normal range and day‐to‐day variability were assessed in normal, unoperated control rats. After completion of transit studies, the rats were euthanized, samples from shielded and irradiated intestine were procured, and radiation injury was assessed with a histopathological scoring system. Median stomach to cecum transit time in unoperated controls was 2.25 hr. The surgical procedure and aging did not significantly affect transit time. Transit time was significantly prolonged both in the 2.8 Gy × 18 group (P = 0.02) and in the 5.6 Gy × 9 group (P = 0.0001). The association between histopathologic radiation injury and transit time did not reach statistical significance. We conclude that non‐obstructing radiation injury in the distal ileum significantly prolongs intestinal transit time and that small bowel follow‐through with barium contrast may be used to assess radiation enteropathy in this animal model. © 1995 Wiley‐Liss, Inc.