PURPOSE: To analyze the small intestinal mucosa ultrastructure, and to characterize the enterocyte lesion severity caused by mechanical intestinal obstruction combined or not with an ischemia of the mesenteric marginal vessels arch. METHODS: It was used 47 Wistar rats divided into 4 groups as follows: Group 1- Control rats (C), Group 2- sham rats (S), Group 3- rats submitted to intestinal obstruction excluding marginal vessel (OEV), Group 4- Intestinal obstruction including marginal vessels (OIV). Rats of groups 3 and 4 were allotted into two subgroups for the removal of small intestinal tissue samples, one at the proximal (P), and the other at the distal (D) segments from the obstruction site. Samples of groups 2, 3, 4 were obtained 24, 48, and 72 hours after post operation care. Small intestinal tissue samples of group 1 were excised following laparotomy. Imaging in Light and Transmission Electronic Microscopy were used for morphological and morphometric studies. The results were analyzed by using the ANOVA and Newman-Keuls tests. RESULTS: No irreversible lesion was observed. In the 24 hours microvilli volume of group 3 turned down at the proximal site henceforth enlarging very slowly within the next 72 hours. At the distal site significant microvilli shrinkage was observed up to 48 hours. Then they recovered their volume after 72 hours. In the 24 hours microvilli volume of group 4 grew twice in comparison with the microvilli of group 1 rats but after 72 hours there was drastic volume shrinkage, shape alterations, and severe flatness, especially in the distal segments of the obstruction site. CONCLUSIONS: Terminal ileum mechanical obstruction with mesenteric marginal arch ischemia led to reversible ultrastructural alterations after 72 hours, and the injury is proportional to the persistence of the obstructive process. Furthermore the mesenteric vessels of the marginal arcade play an important role in the maintenance of mucosal integrity, when such obstructive disorder is present.
Microscopy Electron, Transmission; Intestinal Obstruction; Intestinal Mucosa; Intestine, Small; Animal Experimentation; Rats
