Repercussions of Extensive Small Bowel Resections in Growing Rats N. Lanzoni, J.L. Martins, E.F.S. Montero, F.R.S. Patrı´cio, and Y. Juliano ABSTRACT Objective. To study the effects of extensive intestinal resection on growing rats, with regard to animal weight and histomorphometry of the remaining small intestine. Methods. Forty growing rats were allocated according to the extent of small intestine resection: 60%, 70%, 80%, or 90%. The animals were weighed every week and observed for 30 days. Following sacrifice the remaining small intestine was resected, fixed in 10% formol for 24 hours, embedded in paraffin, and stained using hematoxylin and eosin. The histological changes in the remaining small intestine were assessed for the length and thickness of villi, the thickness of the muscle layer, and the number of intestinal glands. Results. All growing rats showed a fall in body weight, although it was more significant with the largest intestinal resection (80% and 90%). Villus length and muscle thickness increased after 30 postoperative days in all rats, but the number of intestinal glands remained unaltered. Conclusion. Growing rats with greatest resection of small intestine (80% and 90%) had better intestinal adaptation and slower recovery of body weight. E XTENSIVE INTESTINAL RESECTION is a major problem in pediatric surgery because of the serious clinical alterations caused by short bowel syndrome. 1 Ad- vances in clinical treatment, especially prolonged parenteral nutrition, associated with adaptive morphological alter- ations in the remaining small intestine have improved the survival of these patients. 2 Considering that experimental animal studies are generally carried out in adults and evaluate only one or two levels of intestinal resection, we decided to perform a comparative study of the small intestine remaining after different degrees of intestinal resection in growing rats, evaluating body weight and histomorphometric characteristics. METHODS This study was approved by the Research Ethics Committee for animal experiments at UNIFESP-EPM (case no. 1475-98). Forty growing male Wistar rats of 35  5 days old and mean weight 216 g were allocated into four groups: group 60 (G60) rats underwent 60% resection; group 70 (G70), 70% resection; group 80 (G80), 80% resection; and group 90 (G90), 90% resection of the small intestine. The level of intestinal resection was calculated from the Treitz angle to the ileocecal valve (representing 100%). The resection was performed in an equidistant manner from the Treitz angle and ileocecal valve, with preservation of this valve, and a cross-sectional fragment of the jejunum was collected for morpho- logical study. The intestinal anastomosis was end-to-end with interrupted 6-0 nylon stitches. After the first operation, the rats were weighed every week and observed for 30 days. A second operation (euthanasia) was then performed to remove the remaining small intestine, which was processed in the same as the first sample for hematoxylin-eosin staining. The morphometric analysis (villi width and length, muscle From the Divisions of Pediatric Surgery (N.L., J.L.M.), Opera- tive Technique and Experimental Surgery (E.F.S.M.), Pathology (F.R.S.P.), and Biostatistics (Y.J.), Sa ˜ oPaulo Federal University– Paulista School of Medicine (UNIFESP-EPM), Sa ˜ o Paulo, Brazil. Address reprint requests to Edna Frasson de Souza Montero, Al Espada, 134, Alphaville 11, Santana de Parnaı´ba, 0654-395 Sa ˜ o Paulo, Brasil. E-mail: efsmontero.dcir@epm.br Table 1. Preoperative and Postoperative Body Weight (g) of Studied Rats Group Baseline Week 1 Week 2 Week 3 Week 4 G60 239 225 254 268 292 G70 225 213 229 247 265 G80 183 173 201 225 249 G90 216 184 198 215 226 Baseline: body weight before intestinal resection; week 1: postoperative day 7; week 2: postoperative day 14; week 3: postoperative day 21; week 4: postoperative day 30. © 2004 by Elsevier Inc. All rights reserved. 0041-1345/04/$–see front matter 360 Park Avenue South, New York, NY 10010-1710 doi:10.1016/j.transproceed.2004.03.048 Transplantation Proceedings, 36, 1009 –1011 (2004) 1009