Evaluation of the microcirculation of the equine jejunum and ascending colon after ischemia and reperfusion

Intramural vascular patterns of the jejunum and colon were evaluated during ischaemic strangulation obstruction (ISO, 70 min) and subsequent reperfusion (60 min) in 7 adult anaesthetized horses. Microvasculature of experimental and control segments was described by comparison of results from microangiography, light microscopy, and scanning electron microscopy of vascular replicas. Experimental and control segments with isolated vascular arcades were removed either immediately after the experimental period or after 60 min of reperfusion. Blood was flushed from the vascular system by use of isotonic NaCl, and the segments were divided. Half of each segment was perfused with a modified radiopaque medium for microangiographic evaluation, and half was perfused with dilute methyl-methacrylate to create a vascular replica to be studied by scanning electron microscopy. Microangiographic sections also were evaluated for histological changes. In jejunal ISO segments, intramural perfusion was redistributed away from the mucosa. In the villi, the central arteriole was short and convoluted and the subepithelial capillaries were not filled. The submucosal vessels and crypt capillaries were congested, compared with those of controls, and the serosal vessels were not filled in the ischaemic segments. Histological grade II-III mucosal lesion was seen in jejunal ISO segments. Reperfused jejunal segments had a transmural hyperaemic response, and previously unfilled capillaries were observed in all intestinal layers. After reperfusion, the mucosal lesion progressed to grade III-IV and a cellular infiltrate and oedema formation were observed in the serosa. The intramural vasculature of the ischaemic and reperfused colon remained unchanged. Minimum histological damage was observed in the colon after 70 min of ISO or after 60 min of reperfusion.