Obstruction of appendix vermiformis causing acute appendicitis. An experimental study in the rabbit.

In an experimental model using the rabbit, the role of obstruction in the pathogenesis of acute appendicitis was studied. Twenty-one animals were anaesthesized and underwent laparotomy. The appendices were obstructed by a balloon catheter introduced via a caecostomy. Pressures inside the obstructed appendices were measured by a balloon at the tip of the catheter. The abdominal cavity was closed, anaesthesia was continued, and pressure were registered regularly up to 12 hours afterwards in those animals which remained alive during this period. The animals were then sacrificed, and at autopsy evidence of obstruction, distention and inflammatory changes, both gross and microscopic, was registered. In a total of 15 rabbits, experimental obstruction of the appendix resulted in inflammatory changes in the wall of the appendix, which histologically in all respects were similar to appendicitis in man. In the remaining 6 rabbits, either spontaneous release of obstruction or death early during the experiment occurred. Our experimental data suggest that obstruction is an important agent in the causation of acute appendicitis.