MODERATE DOSES OF INTRAOPERATIVE RADIATION SEVERELY SUPPRESS EARLY STRENGTH OF ANASTOMOSES IN THE RAT COLON

Intraoperative irradiation appears to be a valuable addition to the mo dalities available to treat patients with large bowel cancer. However, its potential effect on healing of anastomoses has not been investiga ted extensively. For this purpose, male Wistar rats underwent colonic resection. Subsequently, 1 cm of each bowel end was irradiated with do ses of 10, 15, 20 or 25 Gy and intestinal continuity was restored. Aft er 3 or 7 days, animals were killed and the anastomoses were analyzed for bursting pressure (intraluminal force), breaking strength (longitu dinal force) and hydroxyproline content. Intraoperative irradiation le d to a massive (40-70%) and significant (P < 0.025) reduction in burst ing pressure 3 days after operation compared to the control group for every dose used. After 7 days, the bursting site was outside the area of the anastomosis in all groups. The breaking strength at day 3 was a lso reduced, even after 10 Gy. At day 7, when tearing still occurred i n the wound area, the breaking strength was still significantly lower in the 15- and 25-Gy groups than in the control group. The hydroxyprol ine content of the anastomoses was significantly reduced only after ir radiation with the higher doses. Thus intraoperative irradiation const itutes a threat to early strength of anastomoses in the rat colon, and even at moderate doses it may threaten the integrity of the anastomos is. (C) 1998 by Radiation Research Society.