Background: Surgical neonates with complex intestinal conditions, such as enterocolitis, midgut volvulus with bowel loss and multiple atresias, often require temporary stomas. Little is known on the postsurgical response of the altered gut segments, although adaptation is an important consideration in neonatal postoperative care, particularly after stoma closure.
Materials and methods: Rats underwent bowel resection at a point 15 cm proximal to the ileocecal valve, and a split ileostomy was performed. On the 6th postoperative day the mucosal thickness was calculated with Soft Imaging System Analysis Pro, the rate of proliferation was measured following Ki67 immunohistochemistry and the apoptotic index was determined on sections stained with ApopTag Plus. The intestinal motor activity was recorded on isolated gut segments. Neuronal nitric oxide synthase (nNOS) expression and distribution was examined with NADPH-diaphorase histochemistry and Western blot analysis.
Results: An increased wet weight of the mucosa and a pronounced mucosal thickening were observed in the proximal functional bowel segment. Enterocyte proliferation rate was increased significantly, while the apoptotic index remained unchanged in the epithelial layer. The dilation of the gut lumen resulted in a morphological change in the nitrergic myenteric network with an overexpression of nNOS. As a consequence of the surgical procedure, the functional proximal gut segment showed strong and frequent contraction waves, with an enhanced responsiveness to cholinergic stimuli.
Conclusions: The dilated functional bowel segment was characterized by hyperplasic changes in the mucosa and stronger mechanical activity with overproduction of nNOS. Although early restoration of intestinal continuity is recommended, our observations on adaptive changes may partly explain intestinal motility disorders after early stoma closure, suggesting the need for a careful approach to a redo-laparotomy.