Randomized controlled trial of cyclosporine for treatment of perianal fistulas in dogs.

OBJECTIVE

To evaluate efficacy of cyclosporine for treatment of perianal fistulas in dogs.

DESIGN

Randomized, controlled trial.

ANIMALS

20 German Shepherd Dogs with naturally developing perianal fistulas.

PROCEDURE

10 dogs were treated with cyclosporine; the other 10 dogs were given a placebo. Overall improvement and change in total surface area of involvement and depth of the deepest fistula were determined after 4 weeks. Thereafter, cyclosporine-group dogs were treated for an additional 12 weeks and control-group dogs were treated with cyclosporine for 16 weeks.

RESULTS

All cyclosporine-group dogs, but none of the control-group dogs, were subjectively improved after 4 weeks. Mean total surface area and mean fistula depth decreased 78 and 62%, respectively, in the cyclosporine-group dogs but increased 29 and 11%, respectively, in the control-group dogs. After 16 weeks of cyclosporine treatment, fistulas had healed in 17 (85%) dogs. However, fistulas recurred in 7 of 17 dogs, and additional cyclosporine treatment or anal sacculectomy and surgical excision of fistulas was necessary.

CLINICAL IMPLICATIONS

Cyclosporine appeared to be effective in dogs with perianal fistulas. Even in dogs in which fistulas were not completely healed, cyclosporine administration appeared to be beneficial, because the surgical procedures that were required were less extensive than those that would have been necessary if cyclosporine had not been given.