Etiology of intestinal damage in gastroschisis. I: Effects of amniotic fluid exposure and bowel constriction in a fetal lamb model.

Gastroschisis is often complicated by damage to the herniated small bowel, resulting in motility and absorption disturbances and occasional intestinal necrosis and atresia. To study the pathophysiology of this process, a model of gastroschisis was developed in fetal lambs. At 80 days' gestation, the anterior abdominal wall was partially excised to create a small peritoneal cavity, and the small bowel was extruded through a Silastic ring to create a defect of uniform size. In one experimental group, a tie was placed around the herniated bowel at the level of the abdominal wall to provide gradual constriction as the fetus grew. In a second group, no tie was placed. Control animals had a simple laparotomy and no abdominal wall defect; some also had a constrictor placed around the base of the bowel. The animals were delivered near term, and the bowel was evaluated histologically and by an in-vitro bowel motility assay. Histologic examination showed normal ganglion cells in all groups and no evidence of ischemic injury. A fibrous peel was seen only in bowel exposed to amniotic fluid, with or without a constrictor. Lymphatic and venous dilation, smooth-muscle thickening, and focal mucosal blunting were seen in bowel subjected to chronic obstruction by a constrictor, regardless of whether it was exposed to amniotic fluid. Both constriction of the bowel and amniotic fluid exposure were associated with a decrease in motility; these two effects were independent and additive.(ABSTRACT TRUNCATED AT 250 WORDS)