QS69. Two Experimental Models for Generating Abdominal Adhesions

Abstract

Purpose: Students of experimental adhesion methodology have regularly noted discrepant results between laboratories, probably attributable to variable Methods for inducing adhesions and to different criteria for quantifying results. The purpose of these experiments was to develop dependable rat models for generating abdominal adhesions that allow for objective evaluation and quantification. Methods: Two new adhesion models were compared with classical side-wall models involving cecal abrasion and peritoneal excision or abrasion. Cecal Abrasion: The cecum was exteriorized and the medial surface abraded with dry gauze over a 1 by 2 centimeter area. A similar area of the adjacent side-wall peritoneum was abraded or was excised, leaving the underlying muscle exposed. MODEL T (tissue): a 2.5 by 2.5 cm segment of full-thickness abdominal wall was excised and the overlying skin incision closed, exposing the viscera to subcutaneous tissue; MODEL M (mesh): involved removal of an identical segment, replacing the defect with a 2.5 by 2.5 cm polypropylene mesh sewn to the cut edges. This exposed the viscera directly to the mesh surface. Seven days after operation the character and extent of the adhesions were assessed at autopsy. Results were expressed as the percent area of subcutaneous tissue involved (T) or of mesh surface involved (M). For model T the percent involvement of the circumference of the defect edge was also recorded. The extent of omental and intestinal adhesions were evaluated individually. Results: The classical side-wall models showed inconsistent patterns of adhesion formation and were difficult to evaluate. Every animal from both models M and T developed extensive adhesions. The mean coverage of mesh surface (M) was 93 percent and subcutaneous surface (T) 82 percent. In model T the mean involvement of the defect cut edge was 80 percent of the circumference. All model T animals had both intestinal and omental adhesions. Tenacity of adhesions did not differ significantly between animals or models. Conclusions: Adhesion models M and T are consistent and predictable. Each yields extensive adhesion coverage of a defined two dimensional site which allows for standardized measurement. Adhesion quality varies little among animals with these preparations. The relative ease of preparation and of assessment should make for ready comparison among laboratories and credible results regarding prevention strategies. Tabled 1Adhesion Involvement Adhesions to abdominal wall Adhesions to cecum Mean mesh or SQ surface, % area Mean cut edge, % circumference Structure(s) adhered Small bowel Omentum Cecal Abrasion + Peritoneal Abrasion 50% (7/14) 50% (7/14) NA NA 4 5 Cecal Abrasion + Peritoneal Excision 59% (13/22) 73% (16/22) NA NA 5 14 Model M NA NA 93% (39/39) NA 0 39 Model T NA NA 82% (15/15) 80% 15 15 SQ: subcutaneous, NA: not applicable. Open table in a new tab SQ: subcutaneous, NA: not applicable.