Mucosal morphology in experimental intestinal atresia: Studies in the chick embryo

Abstract

Lesions identical to those observed in human intestinal atresia (IA) have been experimentally reproduced in several mammal models by either mesenteric vessels or intestinal wall injury. The recent availability of an avian model led us to investigate whether the same lesions could be studied at less expense. An intestinal loop within the body stalk hernia was coagulated on the 12th incubation day in 427 chick embryos (group 3), the lesions were studied in survivors 4 days later under light and scanning electronmicroscopy (EM), and the findings were compared with those in 12 control embryos (group 1) and 14 sham-operated ones (group 2). Types I or II atresias were obtained in 61 (73.4%) of the 83 survivors in group 3. Seromuscular layers were normal at both ends of the lesion; there was some flattening of villi at the proximal, dilated end, and hyperplasia with apparently lengthened, branched villi at the distal, unused one. Mucosal pattern under light microscopy was strikingly close to that observed in human IA and in the fetal lamb experimental model. On the other hand, scanning EM showed that in this model there were no villi as such, but rather prominent mucosal folds that were regularly arranged in a tire-rubber pattern in the normal intestine, flattened and distended in the dilated one, and again roughly normal in the distal unused gut. High-power magnification scanning EM showed that enterocytes were normal at all levels but, in agreement with previous findings in the fetal lamb model, that intercellular spaces were widened in the dilated portion adjacent to the obstruction. It is concluded that the apparent hyperplastic aspect of distal atretic intestine could result from mucosal crowding within the unused lumen rather than from true villous enlargement. This study suggests that a chick embryo IA fetal model allows further investigation of the processes of intestinal adaptation after fetal insult at much lower prices than other experimental models.