🔍 What Is Histiocytic Ulcerative Colitis?

Histiocytic ulcerative colitis (HUC) is a rare inflammatory disease of the large intestine in cats, characterized by ulceration of the colon lining with infiltration of PAS-positive histiocytes—a subtype of macrophages—resulting in mucosal damage, diarrhea, and tenesmus :contentReference[oaicite:3]{index=3}.

⚠️ Causes & Risk Factors

• Unknown origin: Considered idiopathic, with suspected infectious (e.g. E. coli) or genetic triggers :contentReference[oaicite:4]{index=4}.
• Age & breed: Typically seen in young to middle-aged cats; occurrence isn’t limited to any specific breed, though boxer-like granulomatous colitis in dogs is well-known :contentReference[oaicite:5]{index=5}.

🚩 Clinical Signs

• Large-bowel diarrhea: Mucus, frank blood, urgency, increased frequency :contentReference[oaicite:6]{index=6}.
• Tenesmus: Straining to defecate, often with little output :contentReference[oaicite:7]{index=7}.
• Weight loss & debilitation: Occasionally seen in advanced cases :contentReference[oaicite:8]{index=8}.

🔬 Diagnostic Steps

1. Rule out common causes: Fecal tests, cultures, parasites, dietary intolerance :contentReference[oaicite:9]{index=9}.
2. Colonoscopy: Visualizes ulcers, granulation tissue, thickening and enables biopsy :contentReference[oaicite:10]{index=10}.
3. Histopathology: Tissue samples show PAS-positive histiocytes, ulceration, crypt distortion and mucosal inflammation :contentReference[oaicite:11]{index=11}.
4. Imaging: Abdominal ultrasound to assess colon wall thickening or lymph nodes :contentReference[oaicite:12]{index=12}.
5. Bacterial culture/PCR: Detects pathogens such as adherent invasive E. coli associated with colitis :contentReference[oaicite:13]{index=13}.

🛠️ Treatment & Management

A. Antibiotics

• Fluoroquinolones or TMP-SMX: Based on culture or empiric protocols—commonly used for several weeks to months :contentReference[oaicite:14]{index=14}.
• Long-term therapy: Many cats require extended courses for remission :contentReference[oaicite:15]{index=15}.

B. Anti-inflammatories & Immunosuppressives

• Sulfasalazine/prednisolone: Used when bacterial treatment alone isn’t fully effective :contentReference[oaicite:16]{index=16}.
• Chlorambucil or cyclosporine: For steroid-refractory or severe inflammatory patterns :contentReference[oaicite:17]{index=17}.

C. Dietary & Probiotic Support

• Moderately fermentable fiber diet: Supports colon health, regularity and stool form :contentReference[oaicite:18]{index=18}.
• Probiotics/fecal transplant (emerging): Combined with antibiotics to rebalance flora :contentReference[oaicite:19]{index=19}.

🏡 Home Care & Monitoring

• Monitor stool: color, consistency, presence of blood or mucus.
• Track weight, appetite, energy levels—record daily and report changes.
• Provide slow access to low-residue food; ensure hydration.
• Use soft bedding and low-stress routine—**Ask A Vet** app can help with reminders and remote checks.
• Stay consistent with diet, meds, follow-up biopsies or scope assessments.

📅 Prognosis & Follow-Up

• Short-term: many cats respond well; diarrhea and tenesmus decrease :contentReference[oaicite:20]{index=20}.
• Long-term: relapse is possible; management often required indefinitely :contentReference[oaicite:21]{index=21}.
• Regular rechecks: colonoscopy at 6–12 months to assess healing, adjust treatment.
• Bacterial cultures may guide therapy if flare-ups occur.

📝 Quick Reference Table