Background/Aims: Anastomoses in previously irradiated intestine are prone to leakage, possibly due to an impeded blood supply. Whether or not chronic radiation damage actually predisposes to a disturbed blood flow in the vicinity of anastomoses was investigated in the rat small bowel. Method: A 2-cm segment of rat ileum was irradiated with a single dose (21 Gy). After 20 weeks an anastomosis was created in the irradiated segment and in the corresponding segment of controls. Another 4 days later local blood flow was studied with the ¹⁴C-iodoantipyrine autoradiography technique in 16 sectors around the circumference both in the anastomotic segment and in a segment 4 mm apart. Results: In the anastomotic segment, the average blood flow was reduced in irradiated compared with non-irradiated animals in the mucosal layer (p = 0.034), but not in the muscular layer (p = 0.08). In the mesenteric quadrant blood flow was reduced in irradiated compared with non-irradiated animals, both in the mucosal layer (p = 0.012) and in the muscular layer (p = 0.05). More irradiated than non-irradiated animals showed a blood-flow reduction to 15% or more in 13–16 sectors both in the mucosal (p = 0.015) and the muscular layer (p = 0.04). Conclusions: The results favor the hypothesis that anastomoses in previously irradiated intestine are vascularly compromized and thereby have an increased risk of leakage.

Anastomoses in an intestine with chronic radiation damage are prone to leakage, possibly due to a reduced blood supply induced by a reduced capillary bed. In an animal model, the numerical capillary density in the perianastomotic area was investigated in intestine with or without chronic radiation damage. A 2-cm segment of rat ileum received a single dose of 21 Gy. Twenty weeks later, when the chronic radiation-induced changes were established, an anastomosis was constructed in this segment and in a corresponding segment in control rats. In situ perfusion fixation of the intestine was done 4 or 7 days after construction of the anastomosis, sections of the intestine were removed surgically, the specimens were embedded in methacrylate plastic and sectioned at 2.5 microm, and capillaries were counted under a light microscope. The circumferential mucosal capillary density was lower in irradiated than in nonirradiated animals at both 4 and 7 days (P < 0.001 and P = 0.04, respectively). This reduction was greater in the mesenteric quadrant than in the other quadrants around the circumference. These results are indicative of a reduced capillary bed in the vicinity of anastomoses in intestine with chronic radiation damage, which might lead to an impeded blood supply and subsequent leakage.