Management of perianal fistulae in five dogs using azathioprine and metronidazole prior to surgery

Objective To evaluate combination therapy with azathioprine and metronidazo le in German Shepherd Dogs with perianal fistulae. Design Prospective study Procedure Five dogs (31.5 to 36.0 kg) with perianal fistulae were treated w ith azathioprine (50 mg per dog orally every 24 h) and metronidazole (400 m g per dog orally every 24 h). Patients were re-evaluated at 2 week interval s by inspection, palpation, photographs of the perineal region and assessme nt of white blood cell counts where possible. Treatment was continued until improvement in lesions reached a plateau. Surgical excision of residual fi stulae and anal sac remnants was then performed, with medical therapy conti nued for an additional 3 to 6 weeks. Result Signs attributable to anal irritation were reduced or eliminated in all dogs within 2 weeks, although visible healing of lesions progressed mor e slowly. Ulcerated lesions reduced in surface area and depth, and some fis tulae healed completely. Non-healing areas were usually associated with ana l sac rupture or chronic fibrosis. Visible improvement typically reached a plateau 4 to 6 weeks after commencing treatment. Immunosuppressive therapy continued for 5 to 24 weeks before surgical intervention to remove anal sac s (four dogs) and/or residual fistulae (five dogs). All dogs remain disease free 7 to 10 months postoperatively. No important complications of treatme nt were encountered. Conclusion Azathioprine with metronidazole effectively reduced perianal irr itation, and the severity and extent of lesions prior to surgery. Treatment was economical even in large dogs and associated with few untoward sequela e. The combined use of immunosuppressive and antimicrobial therapy followed by surgery minimised potential morbidity associated with aggressive use of either medical of surgical treatment alone.