Feline inflammatory bowel disease (IBD)

Symptoms an owner can spot at home

• Chronic or intermittent vomiting (more than once a week for weeks or months, not just occasional hairballs)
• Chronic soft stool, diarrhea, or blood or mucus in stool
• Gradual weight loss despite normal or increased appetite
• Decreased appetite in advanced cases
• Poor coat condition

When to see a vet

• Any cat vomiting more than once or twice a week over a period of weeks, 'my cat just has a sensitive stomach' has been the delayed presentation of many intestinal lymphoma diagnoses
• Progressive weight loss, particularly in a middle-aged or older cat
• Blood in vomit or stool, black tarry stool, or refusal to eat

What it is

IBD is a group of chronic enteropathies characterized by infiltration of the intestinal wall with inflammatory cells. The exact cause is unknown but involves an inappropriate immune response to normal gut microbiota and dietary antigens in genetically predisposed cats. Small-cell (low-grade) intestinal lymphoma is on the same clinical spectrum and often coexists, distinguishing the two requires full-thickness biopsy with immunohistochemistry and PARR clonality testing.

Vomiting hairballs 'occasionally' is normal; vomiting hairballs or bile weekly is not. The chronic vomiting narrative was normalized for decades and is now understood as a clinical sign requiring workup, not a species trait.

How vets diagnose it

Workup includes bloodwork with cobalamin and folate, urinalysis, T4 (rule out hyperthyroidism), fecal parasite testing, and abdominal ultrasound. Definitive diagnosis and differentiation from lymphoma requires biopsy, endoscopic biopsy is less invasive but samples only mucosa; surgical full-thickness biopsy is more diagnostic when muscularis or serosal involvement is suspected. A hydrolyzed or novel-protein diet trial for 6-8 weeks is often used early as both a diagnostic and therapeutic step.

Treatment overview

This is editorial overview, not a treatment plan. Management is stepwise: dietary elimination trial (hydrolyzed or novel protein) first, then vitamin B12 supplementation if cobalamin is low, then immunomodulatory drug class (corticosteroid, chlorambucil in more severe cases) added when diet alone is insufficient. Small-cell lymphoma is treated with a low-toxicity chlorambucil-based protocol and has a median survival often exceeding 2 years, which is why the distinction from IBD matters less than it once did but still guides prognosis.

What owners can do

• Do not normalize chronic vomiting; workup after 3-4 weeks of persistent weekly vomiting.
• Weigh your cat monthly, gradual weight loss is easy to miss visually in longhairs.
• Feed a stable diet and change flavors within a limited protein source if you must rotate.
• Address environmental stress (multi-cat conflict, litter box hygiene), stress worsens IBD flares.