This study compared the severity of ischemic injury to the equine jejunal mucosa caused by arteriovenous obstruction (AVO) or venous obstruction (VO) with that caused by reperfusion after ischemia. The degree of mucosal damage and regeneration was scored according to a modified version of an established light microscopic classification for ischemic injury. Biopsy specimens taken after 3 and 4 hours of obstruction, and after 3 hours of obstruction and 1 hour of reperfusion, were compared. There were no changes in the severity of mucosal injury (characterized by epithelial sloughing, loss of villus architecture, and necrosis of crypt cells) at 4 hours of ischemia when compared with 3 hours of ischemia. The mucosal injury score increased by one grade in three of six and five of eight segments during reperfusion for the VO and AVO models, respectively; however, only the scores for the AVO model were significantly different from the injury caused by ischemia alone. Modification of reperfusion injury was attempted by the administration of intravenous (IV) allopurinol, dimethyl sulfoxide (DMSO), or intraluminal oxygen insufflation at the time of release of the AVO and VO. Treatments did not significantly alter either the severity of injury noted after 1 hour of reperfusion or the degree of mucosal regeneration after 48 hours of reperfusion. In this group of ponies, the severity of mucosal damage was greater after 1 hour of reperfusion for both AVO and VO.

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