Estudo morfológico e imuno-histoquímico do plexo mientérico das válvulas confeccionadas no colo de ratos submetidos à amputação abdominoperineal e colostomia perineal

Abstract

Definitive abdominal colostomy (DAC) following abdominoperineal amputation is an established surgical technique, but it is not free of morbidities. The technique proposed for avoiding DAC is abdominoperineal amputation with perineal colostomy, as it meets the current requirements for the treatment of rectal cancer because it does not interfere with the radicality of the proposed surgery, avoids the need for definitive abdominal colostomy, fills the pelvic hollow and is contentive. The valves constructed in the intestinal segment to make the perineal colostomy continent must be studied from a histological point of view. The goal is contribute towards the elucidation of the mechanisms that promote the retardation of the intestinal contents or partial continency. The aim is to study the morphological and immunohistochemical studies of the myenteric plexus of the valves manufactured and the third valve and the adjacent muscle layers and connective tissue of the intestinal wall adjacent to the third valve. A total of 36 rats were operated on, which were distributed into 3 groups. In the Simulated Group, 6 animals were subjected to a laparotomy. In the Amputated Group, 6 animals were subjected to the amputation of their sphincter structure and to perineal colostomy. In the Amputated Group with Valve, 24 animals underwent three seromyotomy procedures (section of the serous muscular, longitudinal, myenteric plexus and circular muscular layers) on the pulled-through colon, the amputation of the sphincter structure and perineal colostomy. On the 40th postoperative day the intestinal segment underwent morphological and immunohistochemical study in the following manner: descriptive microscopy (Hematoxylin and Eosin stain) on the segment operated on, at the site of the seromyotomy and upstream and downstream of the third valve; morphometric and immunohistochemical analyses (Protein Gene Product 9.5 which confirms the existence of the enteric nervous system elements) at the location of the seromyotomy and upstream and downstream of the third valve; Gomori trichrome stain and the linear measurement of the thickness of the serous, longitudinal muscular and circular muscular layers upstream and downstream of the third valve. The descriptive microscopy (Hematoxylin and Eosin stain) of the intestinal wall in the region of the valve reveals a chronic inflammation, cicatricial, with fibrous replacement tissue, restricted to the location, and a microscopic linear interruption of muscle layers, a region which presents deposits of collagenous and vascular conjunctive tissue, with an absence of enervation at the seromyotomy site. A systematic observation of the areas adjacent to the valve shows that the structural aspect of the longitudinal and circular muscular layers was preserved. Coloration with Gomori trichrome stain shows deposits of collagen mainly in the area near the surgical intervention, without revealing quantitative differences among the groups in the areas adjacent to the third valve. The thicknesses of the muscle layers, both longitudinal and circular, did not vary significantly in the samples studied. Immunoexpression of Protein Gene Product 9.5 demonstrates the total absence of nervous elements and of the myenteric plexus at the site of the valve. The density of the nervous elements of the circular muscular layer at sites adjacent to the 3rd valve was not statistically different. The conclusion of the morphological and immunohistochemical study of the valves constructed in the left colon of rats subjected to abdominoperineal amputation and perineal colostomy shows the denervation at the serotomy site, which contributes to the retardation of the intestinal flow and the preservation of the muscular elements, of the conjunctive tissue, of the nervous elements and of the myenteric plexus of the intestinal wall at the intervalvular sites