Morphologic alterations observed during experimental ischemia of the equine large colon

Morphologic changes that develop sequentially in the large colon during experimentally induced ischemia were documented in 14 halothane-anesthetized horses. Colonic ischemia was induced by 4 types of vascular occlusion, 24 cm proximal and distal to the pelvic flexure. The effect of transmural (colonic wall) vascular compression combined with either venous occlusion (3 horses, group A) or venous and arterial occlusion (3 horses, group B) of the colonic vessels was studied for 1, 2, and 6 hours of occlusion. Also observed was the effect of reperfusion for 0.5 hour after release of the clamps for the 1- and 2-hour occlusions and for 1 hour after release of the clamps for the 6-hour occlusion. Effects of occluding only the colonic veins (4 horses, group C), or the colonic veins and arteries (4 horses, group D) were studied for 0.5, 1, 1.5, and 2 hours of occlusion and during reperfusion for 0.5 hour. Full-thickness intestinal biopsy specimens were obtained from the antimesenteric border of the pelvic flexure at 0, 0.25, 0.5, 0.75, 1, 1.5, and 2 hours during occlusion and at 0.5 hour after release of vascular occlusion. Biopsy specimens were obtained at hourly intervals from the 2 horses in which 6-hour occlusion was performed and at 1 hour after release of vascular occlusion. Macroscopic changes (serosal color, mucosal color, serum leakage) in the colon were recorded.(ABSTRACT TRUNCATED AT 250 WORDS)