INTRODUCTION: A temporary stoma is a relatively common procedure at the neonatal age for a number of disorders. At birth, the enteric nervous system (ENS) is not fully developed; temporary colostomy causes morphological changes in the ENS. We studied whether transection of bowel or deprivation of stool is responsible for these changes. Moreover, reversibility of the ENS changes after stoma closure was investigated. METHODS: Male Lewis rats aged 3 weeks were randomly divided into 3 groups. Group 1 (stoma group) received a stoma (t = 0), stoma closure 2 weeks later (t = 1), and were killed 2 weeks after stoma closure; group 2 (transection group) had a colon transection and immediate anastomosis (t = 0) and were killed 2 weeks afterward. Group 3 (sham group) had no operation. In all groups, the nerve/muscle fiber ratio (NMR) in the proximal and distal colon was assessed with full thickness biopsy specimens at operation or after killing. The NMR in the stoma, transection, and sham group at t = 1 were used to assess the effect of deprivation of passage of feces and transection itself on the development of the ENS of the colon. Results of the stoma group at t = 1 and t = 2 were compared to assess possible reversibility of ENS changes after stoma closure. RESULTS: There was a significantly higher NMR in the distal colon compared to the proximal colon in both the stoma and transection groups at t = 1 (2.0 +/- 0.38, P < .001 and 2.8 +/- 0.97, P < .001, respectively), whereas there was no significant difference in NMR ratio at t = 1 (1.1 +/- 0.18, P = .34) in group 3. In group 1, the NMR ratio increased further after stoma closure to 3.1 +/- 0.37, P < .001, at t = 2. CONCLUSION: Transection of the bowel rather than deprivation of fecal passage causes nerve fiber hypertrophy in the distal colon of neonatal rats. Restoration of bowel continuity does not result in recovery of these ENS changes. AD - Department of Surgery, University Hospital Maastricht, 6202 AZ Maastricht, The Netherlands.