A standardized protocol for anal fistula induction in a rat model.

PURPOSE: To evaluate an experimental model of anal fistulas in rats, analyze the primary challenges associated with this model, and identify its key advantages.

METHODS

Twenty-six male Wistar rats underwent surgical induction of two anal fistulas each, using a metal seton. The setons remained in place for 30 days, after which they were removed. Animals were divided in two groups (n = 13 per group). Group 1 was euthanized two weeks post-seton removal, and Group 2 in four weeks post-seton removal. Two fistula tissue samples were collected from each animal for histopathological analysis.

RESULTS

All 26 animals tolerated the procedure well, with an average weight gain of 64.3 grams in 30 days. There was no animal loss during the experiment, but eight setons were lost due to poor fixation. One animal lost both setons and had to be excluded from the experiment, resulting in a 96% success rate. All 44 remaining fistulas could be identified by observing the scar on the external orifice, two and four weeks after the removal of the metal wire.

CONCLUSION

The two groups showed no differences. The experimental model in this work proved to be quite effective, economically viable and easy to reproduce.