Randomized controlled trial demonstrates nutritional management is superior to metronidazole for treatment of acute colitis in dogs.

To describe the outcome of dietary management of canine noninfectious acute colitis with or without concurrent oral administration of metronidazole using a randomized controlled clinical trial. 59 client-owned dogs with noninfectious acute colitis. Dogs with acute noninfectious colitis were enrolled in a 30-day diet trial after exclusion of parasitic infectious etiologies (fecal centrifugation floatation, Giardia/Cryptosporidium antigen testing) and systemic disease (CBC, biochemistry, urinalysis). Dogs were randomized into 3 placebo-controlled groups: group 1, easily digestible diet + placebo tablet; group 2, easily digestible diet + metronidazole tablet; and group 3, psyllium-enhanced easily digestible diet + placebo tablet. Dogs were evaluated serially using fecal scoring for time to remission, average fecal score, relapse after remission, and dysbiosis index. Median remission time was significantly different among the 3 groups (P < .01) with median times of 5 days (range, 4 to 10) for group 1, 8.5 days (range, 7 to 12) for group 2, and 5 days (range, 3 to 6) for group 3. Metronidazole addition affected the fecal dysbiosis index negatively at days 7 to 10. No adverse effects or complications were noted throughout the study. For canine noninfectious acute colitis, dietary management with an easily digestible diet with or without psyllium enhancement proved a superior management strategy compared to metronidazole. The omission of metronidazole reduced the adverse impact significantly on intestinal microbiota. Longitudinal clinical trials are necessary to compare the long-term response, stability, and complications associated with dietary management alone versus combined dietary and antimicrobial therapy for canine acute colitis.