Evaluation of the microcirculation of the equine small intestine after intraluminal distention and subsequent decompression

Effects of intraluminal distention (25 cm of H2O, 120 min) and subsequent decompression (60 min) on intramural vascular patterns of the small intestine was evaluated in 7 anaesthetized horses. Intraluminal distension (25 cm of H2O, 120 min) was created in 2 jejunal segments in each horse. Experimental and control segments were removed either immediately after the experimental period or after 60 min of decompression. The vascular system of experimental and control jejunal segments was lavaged with NaCl, then injected with a blue-coloured radiopaque medium for microangiography or with a diluted methyl methacrylate for scanning electron microscopy of microcorrosion vascular casts. After angiographic evaluation, tissue sections were prepared for light microscopic evaluation to assess vascular filling and tissue morphology. The distended segments had short villi, which were separated by expanded crypts, and had mesothelial cell loss, neutrophil infiltration, and oedema in the seromuscular layer. The number of perfused vessels was significantly decreased in the seromuscular layer and, to a lesser extent, in the mucosal layer of the distended segments, compared with controls. After decompression, the morphological lesions progressed in mucosal and serosal layers and the number of observed vessels increased in all intramural layers; however, vascular density did not return to the predistention state. It was concluded that these results identify altered intramural vascular patterns in the equine jejunum during luminal distention and subsequent decompression.