Diverting colostomy induces mucosal and muscular atrophy in rat distal colon.

Abstract

The progress of adaptive changes in the left colon after diverting colostomy was studied in rats using stereological techniques. Standardised segments of left colon proximal and distal to the colostomy was examined after 0, 1, 2, 4, or 12 weeks. In excluded colon the mucosal weight was reduced by 37% (p<0-01) and the luminal surface area by 47% (p<0.01) after four weeks and reached a steady state at this point of time, as no further reduction was seen from 4 to 12 weeks. The number of proliferating crypt cells was determined immunohistochemically after in vivo labelling with bromodeoxyuridine and was compared with the total number of colonocytes. Total bowel rest leads to a reduction in the number of proliferating epithelial cells and not to a reduced average life span. The weight of the muscularis propria decreased by 32% after four weeks (p<0.01) and by 48% after 12 weeks (p<0.001), whereas the weight of the submucosa was unchanged. No adaptive changes were found in segments proximal to the colostomy. These results show that the wall composition of defunctioned colon in rats is radically changed resulting from a mucosal and muscular atrophy, and from a reduction in luminal surface area. (Gut 1994; 35: 1275-1281 Multistage procedures that include a temporary colostomy have become the standard approach in the surgical treatment of many emergency and some elective colonic conditions. Although the performance of a colostomy later followed by colostomy closure is regarded as a safe procedure, the latter is still associated with a significant rate of morbidity and mortality.1 2 The complications include anastomotic leak, faecal fistula, and anastomotic obstruction.3 When the faecal stream is surgically divided, the luminal environment and the mechanical stimulation of the colon is radically changed. Although complications after colostomy closure may be related to trophic changes in the defunctioned bowel wall only few studies have been performed to characterise the overall colonic response to surgical defunctioning.Luminal bulk is considered to be important for normal mucosal growth in the entire gastrointestinal tract. Profound mucosal hypoplasia has been found in biopsy specimens taken from the defunctioned rectum in humans,4 and in rat colon reductions in the mucosal cell proliferation and mucosal mass have been shown after total parenteral nutrition,5 fasting,6 and faecal diversion.7-9 The morphometric information in these studies was, however, obtained mainly from isolated crypts, and consequently they did not fulfil modem stereological requirements regarding uniform specimen sampling.'0 Blomquist et alhas shown a decrease in collagen synthesis and collagen content of the entire wall of excluded colon in rats.11 These data show that the atrophic changes occur in all layers after defunctioning the large bowel, but at the present no morphometric information exist to support these findings.The aim of this experimental study was, by means of new and unbiased stereological techniques, to investigate and quan...

Evaluation by computerized morphometry of histopathological alterations of the colon wall in segments with and without intestinal transit in rats

“…After the twelfth week, the thickness of this layer returned to values close to the six weeks values. These findings were in agreement with those of Kissmeyer-Nielsen et al 15 who found a 34% reduction in mucosal muscle layer weight after twelve weeks of intestinal deviation. In the present study it was not possible to demonstrate a linear correlation between the duration of exclusion and modifications to the thickness of the mucosal muscle layer.…”

“…They also observed that, in the segments without transit, the partial volume of the mucosa was significantly smaller in the group with deviation than in the control group. Kissmeyer-Nielsen et al 15 found that there were significant reductions in the weight of the colon mucosa, by 10% after one week, 21% after two weeks, 37% after four weeks and 31% after twelve weeks of intestinal transit exclusion. They observed that the atrophy of the mucosal layer reached significant levels two weeks after the deviation and reached a peak four weeks after the deviation, stabilizing thereafter 14 .…”

“…Although the microscopic structure of the intestinal wall in rats is similar to that of humans, studies evaluating histological changes have generally been carried out in humans and thus they have been subject to interpretational variations due to sample heterogeneity. The use of rats as an experimental model for DC has been proposed, although some authors have not considered this to be an ideal experimentation animal 10,11,15 .…”

“…SCFAs cause greater blood flow to the intestinal wall through diminishing the resistance of the arterioles of the colon and rectum. They promote adhesion between the colonocytes, increase sodium and water absorption, stimulate normal growth of the colon epithelial cells, influence motility and favor healing of intestinal wall lesions 15,16,17 . SCFAs play a protective role in relation to neoplasia development because their antiproliferative action interferes in the cell differentiation process, thereby favoring apoptosis 17,18 .…”

“…Computer-assisted analysis has been used with various objectives and, in relation to conventional methods, it has the advantage of enabling fast and objective quantitative evaluation of the microscopic structures 22,23 . Few studies have evaluated inflammatory alterations in the colon wall of intestinal segments that have been taken out of function, by means of morphometric analysis methods 9,11,15 .…”