A Novel Laparoscopic Surgery Model with a Device to Expand the Abdominal Working Space in Rats: The Influence of Pneumoperitoneum and Skin Incision Length on Postoperative Inflammatory Cytokines

Purpose: Experimental models of laparoscopic surgery generally use large animals owing to a sufficient abdominal working space. We developed a novel laparoscopic surgery model in rats. We performed intestinal anastomosis to demonstrate the feasibility and reliability of this model. Materials and Methods: We designed a device for rats that expanded the abdominal working space and allowed us to manipulate the intraperitoneal organs by hand under direct vision with pneumoperitoneum. We performed small bowel resection and intestinal anastomosis in rats using this model. To elucidate the effects of pneumoperitoneum and skin incision length, rats were randomly divided into four groups with differing surgical techniques: small incision group, large incision group, small incision + pneumoperitoneum group, and large incision + pneumoperitoneum group. Intraoperative abdominal pressure and postoperative cytokines were measured. Results: One experimenter completed small bowel resection and hand-sewn anastomosis under direct vision without any difficulties or assistance. Carbon dioxide pneumoperitoneum was maintained at 8-10 mmHg during surgery in both pneumoperitoneum groups. Necropsies revealed no evidence of anastomotic leakage at 24 h after surgery. The interleukin-6 and C-reactive protein concentrations were significantly greater in large incision group than in small incision group, but were not significantly different between small incision + pneumoperitoneum group and small incision group. These cytokines concentrations were the greatest in large incision + pneumoperitoneum group. Conclusions: Our laparoscopic surgery model in rats is a simple and reliable experimental model. The length of skin incision might be a more influential determinant of surgical invasiveness than pneumoperitoneum.