Granulomatous colitis in Boxers and French Bulldogs: treatment
2-year-old Boxer with 4 months of large bowel diarrhoea with blood and mucus, tenesmus and weight loss. No improvement on a hydrolysed diet or prednisolone. Colonic biopsies show ulcerative colitis with macrophages laden with PAS-positive material, and FISH shows E. coli within the mucosa.
What is the most appropriate treatment?
chevron_right Show answer and explanation
A. An antibiotic that penetrates macrophages, such as enrofloxacin for several weeks, chosen on the basis of biopsy culture and susceptibility
Correct. This is an adherent-invasive E. coli infection, not an immune-mediated disease. Fluoroquinolones clear the intracellular bacteria and usually achieve remission, but resistance is increasing: culture the mucosal biopsy before choosing the drug.
B. Increase the prednisolone and add azathioprine
Escalating immunosuppression worsens an invasive infection. Failure to respond to steroids is precisely a clue pointing to this disease.
C. Metronidazole and sulfasalazine as for idiopathic chronic colitis
They do not eradicate intracellular E. coli; they may improve signs somewhat without curing the disease, which progresses.
D. Subtotal colectomy, because the ulcerative lesions are not reversible
The lesions resolve with an appropriate antibiotic; surgery is not indicated for this disease.
lightbulb Key takeaway
In a young Boxer or French Bulldog with ulcerative colitis unresponsive to diet or steroids, request biopsies with PAS staining and mucosal culture. Avoid short empirical courses of fluoroquinolones: they promote resistance and relapse.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.