Two Experimental Models for Generating Abdominal Adhesions

Purpose: To develop dependable rat models for generating abdominal adhesions that allow for objective evaluation and quantification. Methods: Two adhesion models were devised and compared with conventional side-wall models involving cecal abrasion and peritoneal excision or abrasion. model T (tissue): removal of a 2.5 by 2.5 cm segment of full-thickness abdominal wall with overlying skin closure, exposing the viscera to subcutaneous tissue; model M (mesh): 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% and subcutaneous surface (T) 82%. In model T the mean involvement of the defect cut edge was 80% of the circumference. All model T animals had both intestinal and omental adhesions whereas there were no intestinal attachments in model M. Tenacity of adhesions did not differ significantly between animals or models. Conclusions: Adhesion models M and T are consistent, predictable, and dependable. They each yield extensive adhesion coverage to a defined site, which allow for standardized measurement.