Feline Triaditis: Pancreatitis, Cholangitis and IBD

Triaditis is not one disease but three running at once: pancreatitis, cholangitis, and inflammatory bowel disease, found together often enough that most internists look for all three once one is confirmed. The ducts explain the pattern. In most cats the bile duct and the pancreatic duct open together into the duodenum, so inflamed gut has 2 short roads into the liver and the pancreas. Treatment then follows one rule: treat the branch that is worst, not the average of the three.

Why the three travel together

Anatomy does most of the work. A shared opening means duodenal contents, bacteria included, can reflux into the bile duct and the pancreatic duct at the same pressure that pushes food forward. Cats also mount a strong lymphocytic response in the gut, and lymphocytic cholangitis looks like the same immune reaction one organ upstream. That is why a cat with chronic vomiting and a low cobalamin often turns out to have all 3 problems on ultrasound, and why treating only the gut leaves the jaundice behind.

The practical consequence: when a cat is diagnosed with any one of the three, ask for a fasting bile acid or bilirubin, a folate and cobalamin panel, and an abdominal ultrasound before accepting a single-organ diagnosis.

The fPL number and the 200 µg/L question

Feline pancreatic lipase is the marker most often quoted and most often misread. The older fPL assay reported results where 200 µg/L was the cutoff for abnormal. The current Spec fPL reports on a much smaller scale: under 3.5 µg/L is normal, 3.5 to 5.4 is equivocal, and above 5.4 is consistent with pancreatitis. A printout showing 200 has to be matched to the assay before anyone acts on it, because 200 on the legacy scale and 3.5 on the current one mean roughly the same thing.

Add the liver side: ALT and ALP rising together, GGT up, and bilirubin above 2 mg/dL, which is where jaundice becomes visible in the gums. Cobalamin under about 300 ng/L points to disease in the last part of the small intestine, where IBD usually sits.

Treat the worst branch first

Rank by what will kill the cat in 48 hours, then work down.

• Pancreatitis, if the cat is vomiting and painful. Fluids at 2 to 3 mL/kg/h, maropitant at 1 mg/kg every 24 hours, buprenorphine at 0.01 to 0.02 mg/kg every 6 to 8 hours, and food within 24 to 48 hours. Withholding food for 3 days is the old approach and it makes the liver worse.
• Cholangitis, if bilirubin is climbing. Amoxicillin-clavulanate at 12.5 to 25 mg/kg every 12 hours, or metronidazole at 10 mg/kg every 12 hours, for 4 to 6 weeks. Ursodiol at 10 to 15 mg/kg once daily improves bile flow. Lymphocytic cholangitis gets prednisolone at 1 to 2 mg/kg a day instead of long antibiotics.
• IBD, once the other two are stable. A hydrolyzed or single-protein diet for a 4 to 6 week trial, plus prednisolone at 1 to 2 mg/kg a day, tapered by 25% every 4 to 8 weeks.

Branch, marker, and recheck interval

Branch	Key marker	First 48 hours	Recheck
Pancreatitis	Spec fPL above 3.5 µg/L	Fluids 2 to 3 mL/kg/h, opioid	4 to 6 weeks
Cholangitis	Bilirubin above 2 mg/dL	Antibiotic, ursodiol 10 to 15 mg/kg	2 to 4 weeks
IBD	Cobalamin under 300 ng/L	Hydrolysed diet from day 1	6 to 8 weeks
Bile duct obstruction	Bilirubin above 10 mg/dL	Surgery or stent within 72 hours	7 days
Concurrent diabetes	Glucose above 300 mg/dL	Start insulin at 1 U twice daily	7 to 14 days

Feeding a cat that will not eat

Appetite is the vital sign that matters most in week 1. Aim for 25% of the resting energy requirement on day 1, 50% on day 2, 75% on day 3, and full intake by day 4 or 5. Mirtazapine at 1.88 mg every 48 hours, a quarter of a 7.5 mg tablet, is a common appetite stimulant; it helps some cats and does nothing for nausea. If the cat takes under 50% of its requirement for 3 days running, a feeding tube goes in — a cat that goes 5 days without adequate calories is on the road to fatty liver, which is a far worse problem than the one being treated.

Keep the diet low in fat at 10 to 15% of dry matter while the pancreas is sore, then lift it after 4 weeks if the cat tolerates food well.

Relapse and the follow-up calendar

These cats flare again. A second episode within 12 months is common enough that owners should expect it, and each flare tends to be milder if the first one was treated fully. The calendar: a liver and pancreatic panel at 4 weeks and again at 8 weeks, Spec fPL at 4 to 6 weeks to confirm the number is falling, weight every 30 days, and ultrasound every 3 to 6 months for the first year. Cats with lymphocytic cholangitis that relapse on prednisolone alone are often switched to chlorambucil at 2 mg every other day, with a blood count every 2 weeks for the first 8 weeks.

Two flares in 12 months is the point where most vets stop tapering and settle on a maintenance dose, usually the lowest one that keeps the cat eating and the bilirubin normal.

When to go to the hospital

Jaundice plus 24 hours of not eating, vomiting more than 3 times in a day, weight loss over 10% in 3 months, fever at 40 C or above, fluid building in the abdomen, or any seizure, head pressing, or staring at a wall. Those last signs mean hepatic encephalopathy, and a cat with them is treated in hospital, not at home.

What to do this week

1. Ask which assay produced the lipase result, and get the number on the same scale as the 3.5 and 5.4 cutoffs.
2. Book an abdominal ultrasound plus a bile acid, cobalamin, and folate panel before starting steroids.
3. Start the diet trial on day 1, not after the antibiotics finish; the gut branch runs for 4 to 6 weeks.
4. Weigh the cat every 7 days and photograph the ribs monthly, since a 10% loss is easy to miss on a fluffy cat.
5. Write the recheck dates on the calendar now: 4 weeks, 8 weeks, then every 3 months.

Mouth inflammation often travels with this gut disease, and the chronic gingivitis pattern in /health/feline-fcv-chronic-gingivitis/ is worth checking at the same exam. Cats whose immune system cannot hold herpesvirus down tend to flare together, covered in /health/feline-herpes-long-term/, and /tools/cat-age/ gives the age band that changes how hard to push on biopsies.

Terms mentioned in this article

IBDFCV

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