[Pathological studies on microvasculature of arteriovenous malformation in the intestinal tract].

Intestinal arterio-venous malformation (AVM) is one of the uncommon causes of gastrointestinal hemorrhage and is usually difficult to diagnose before pathological study. Five operated cases with the AVM were presented. The vascular lesions were studied by barium-gelatin injection and routine histological procedures. The AVM lesion was detected in the proximal jejunum and in the distal ileum in each one case, respectively. In two other cases the AVM lesion was observed as a protruded tortuous vascular plexus in colonic mucosa. By the microangiographical study, it was confirmed that the main lesion of AVM was located in submucosal layer with complicating minute AVM in lamina propria of intestinal mucosa. In the mucosal lesion of AVM it was disclosed that arterialization of precapillary arterioles was a remarkable finding. Thickened intimal layer and duplication of internal elastic lamina were recognized in these arteriolar lesions. Two kinds of intestinal AVM were classified, one is located in the submucosal layer and another one is located in mucosal layer. It was suggested that a marked ectasia of mucosal vessels seemed to be a secondary change of the submucosal AVM. The pathogenesis of the mucosal AVM was discussed.