Effect of intraoperative radiation on the tensile strength of small bowel anastomoses

Increasing interest in the use of preoperative or intraoperative radiation therapy for cancer has led to concerns regarding tissue healing and integrity subsequent to treatment. This is especially so for intestinal anastomoses incorporating irradiated bowel, where poor healing may lead to anastomotic disruption and sepsis. One hundred thirty Sprague-Dawley rats were randomized into five groups as follows: both limbs, one limb, or neither limb of an anastomosis received 2,000 R of radiation intraoperatively. A fourth group had a segment of small bowel irradiated, with no anastomosis; a fifth group had the gut exposed by celiotomy. The control groups and all anastomoses underwent tensile strength measurements on the seventh postoperative day, with findings as follows: no anastomosis, no irradiation, 143.75 g; no anastomosis, irradiated, 114.50 g; anastomosis, no irradiation, 85.273 g; anastomosis, one limb irradiated, 78.100 g; anastomosis, both limbs irradiated, 59.00 g. There was no statistical difference in tensile strength of the anastomosis between when neither limb and when just one limb was irradiated. However, when both limbs were irradiated, the loss of strength was statistically significant (P=0.002). Irradiation damage scores were assigned using Blacket al.'s histologic scoring system. These scores were not significantly different between the irradiated segments. Inflammation and fibrosis scores for the anastomoses were also not significantly different. These results indicate that, in rats, anastomotic healing is impaired only when both limbs of the anastomosed intestine are irradiated. The normal strength of the anastomosis with only one limb irradiated cannot be explained by differences in inflammation, fibrosis, or radiation damage and is caused by an undetermined factor.