Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic enteropathy characterized by persistent GI inflammation with no identifiable underlying cause. It is a diagnosis of exclusion.

Clinical signs: Chronic vomiting, diarrhea (small or large bowel), weight loss, poor coat, flatulence, borborygmi.

Classification by histopathology:

• Lymphocytic-plasmacytic: Most common (50–70%)
• Eosinophilic: Less common; may involve stomach
• Neutrophilic: Uncommon; consider underlying infection

Food-responsive enteropathy (FRE): Approximately 50–60% of cats with chronic GI signs respond to a novel protein or hydrolyzed diet without additional medication. This is technically not IBD but falls under the chronic enteropathy umbrella.

Stage 1 — Rule out metabolic/extrinsic disease:

• CBC/Chem/UA (rule out CKD, hyperthyroidism, liver disease, diabetes)
• Fecal flotation + Giardia antigen
• Trial of deworming (fenbendazole) even if fecal negative

Stage 2 — Diet trial:

• Novel protein diet or hydrolyzed protein diet for 4–8 weeks
• Strict adherence — no treats, no table food, no flavored medications
• If response → FRE diagnosed; continue diet

Stage 3 — Imaging:

• Abdominal ultrasound: thickened bowel loops, loss of layering, mesenteric lymphadenopathy
• Radiographs: generally unhelpful for IBD

Stage 4 — Biopsy (gold standard):

• Endoscopic or surgical full-thickness biopsy
• Indicated if no response to diet + steroids, or if neoplasia (lymphoma) suspected

1. Diet:

• Novel protein or hydrolyzed diet (Hill's z/d, Royal Canin HP, Purina HA)
• Continue 8–12 weeks before declaring failure

2. Corticosteroids (if diet fails):

• Prednisolone: 1–2 mg/kg PO q12h initially, taper to q48h over 4–8 weeks
• Budesonide: Alternative with less systemic effects; expensive

3. Immunosuppressants (refractory cases):

• Chlorambucil: 2 mg PO q48-72h for lymphocytic-plasmacytic IBD or if lymphoma cannot be excluded

4. Cobalamin (B12):

• Many IBD cats have ileal disease → B12 malabsorption
• 250 mcg SC weekly x 6 weeks, then monthly

5. Probiotics: Limited evidence; may be beneficial as adjunct.