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Experimental surgery in infrarenal aorta and sigmoid ischemia.

AIM
Colon ischemia is a rare but serious complication in surgery of the infrarenal aorta, due to ligation of the inferior mesenteric artery and the ischemia-reperfusion syndrome. In order to investigate the degree of intestinal damage, we employed experimental surgery in pigs, applying the usual protocol for elective repair of the infrarenal aorta (AAA or Y graft).


METHODS
Three groups of pigs were operated on. In Group A (n=4, 21-25 kg, mean 22.6) a sham operation was performed. In Group B (n=6, 21-26 kg, mean 24) the infrarenal aorta was cross-clamped along with the internal and external iliac arteries and a longitudinal incision was performed in the aorta, while in Group C (n=5, 20-27 kg, mean 23.8) a Pruitt-Inahara shunt was used to allow flow from the infrarenal aorta towards the iliac arteries and the inferior mesenteric artery during cross-clamping. The duration of cross-clamping was two hours (Group B and C). In all groups we evaluated sigmoid histology after reperfusion under light microscopy.


RESULTS
The pathologic examination of the sigmoid revealed increased postischemic injuries in Group B, while the protective effect of the shunt was obvious in Group C. The tissue samples of Group B presented hyperemia, submucosal edema, dilatation of the lymph vessels and severe inflammatory infiltration of the mucosa, muscularis propria and serosa, with cells showing acute and chronic inflammatory responses. In Group C all specimens presented hyperemic vessels and a slight inflammatory reaction of mucosa. In conclusion, Group B, presented the most severe inflammatory changes, involving all layers, while in Group C congestion and slight inflammatory reactions of the mucosa were observed. In Group A, no significant changes in normal histology were observed.


CONCLUSION
The importance of these findings is evident, because in the clinical situation patients have variable degrees of arteriopathy, thus even short periods of ischemia might prove disastrous and this could occur in repair of the infarenal aorta as well as in other cases of inevitable risk, such as in surgery of the thoraco-abdominal aorta.