Cholangitis in a cat is a bundle of 3 diseases sharing one drainage system. Neutrophilic cholangitis is the acute, often bacterial one; lymphocytic cholangitis is the slow, immune-driven one that usually travels with inflammatory bowel disease; and fluke-associated cholangitis is the geographic one. They overlap on a blood panel and on ultrasound, so the diagnosis rests on 4 tests in a fixed order.
Get the order wrong and you either suppress a bacterial infection or chase a liver value for 6 months while a fluke sits in the duct.
Type 1: neutrophilic, the acute one
Bacteria climb from the duodenum into the bile tree and inflame the ducts and periportal tissue. The cat is often 3 to 9 years old, eating poorly for 2 to 5 days, jaundiced, and running a fever above 39.5 C. Blood work shows a neutrophilia with a left shift, a rising total bilirubin, and an ALP that climbs faster than the ALT, often 3 to 10 times the upper limit. The gallbladder may be full of thick sludge.
Here a bile culture changes the plan, because the antibiotic must match the organism, not a guess.
Type 2: lymphocytic, the slow one
An older cat, 8 to 14 years, with weeks of dull appetite, weight loss of 300 to 600 g, and a bilirubin that drifts between 1 and 4 mg/dL. The ALP and GGT are up, the ALT may be normal, and the gamma globulins are often high. The gallbladder wall thickens past 1 mm, the common bile duct may sit at 2 to 3 mm, and the cat frequently has parallel changes in the pancreas and the small bowel, the pattern vets call triaditis.
Lymphocytic cholangitis is not an infection, so antibiotics do not fix it, and the biopsy is what separates it from small cell lymphoma of the liver.
Type 3: fluke-associated
Liver flukes live in the bile ducts, and the inflammation is a reaction to the flukes and their eggs. Geography does the work: a cat from an endemic region, or one that eats raw freshwater fish, moves up the list. Blood work can show eosinophilia, and ultrasound may show a dilated duct with echogenic material inside. Eggs are sometimes found on bile cytology or on a fecal sedimentation, but a negative sediment does not exclude the disease.
Test 1 and 2: blood, then ultrasound
The panel needs 6 values, not 3: ALP, GGT, ALT, total bilirubin, albumin and glucose. GGT is the value most often skipped and the one that best tracks the duct. Add a CBC, a cobalamin and a T4, because an older cat with a low cobalamin and a high T4 changes the plan. Bilirubin above 2 mg/dL usually means jaundice shows in the gums.
Ultrasound gives 4 numbers: common bile duct diameter, gallbladder wall thickness, sludge or mass, and the pancreatic duct. A duct at 2 mm or less is normal in most cats; 3 mm is equivocal; above 4 mm with jaundice points at obstruction and needs a surgeon the same week.
Test 3: the bile sample
Ultrasound-guided cholecystocentesis is the highest-yield single test for type 1 and the only one that gives a culture. It is also the one that can kill the cat, so the guardrails matter. Check platelets above 100,000, PT and aPTT inside reference, and systolic pressure under 160 mmHg. A 22 gauge needle, a transhepatic window, 1 pass, and no more than 2 to 3 ml of bile. If the gallbladder is packed with sludge or the duct is obstructed, many vets skip the needle and go to surgery.
Send the sample for cytology and for aerobic culture, and ask for a direct smear as well: a delay of 2 hours before culture reduces the recovery of fragile organisms. Results take 3 to 5 days. Watch for 24 hours for fever, a tense abdomen or a drop in blood pressure, because a bile leak causes peritonitis fast.
Test 4: biopsy, and the copper question
Histology separates lymphocytic cholangitis from lymphoma and copper-associated hepatopathy. A 14 to 16 gauge sample from 2 lobes suits most pathologists; a surgical wedge shows architecture better. Ask for a copper quantification as well; a dry weight copper above 1,500 ppm changes the management plan and is easy to miss on routine staining.
Four tests side by side
| Test | What it answers | Flag value | Turnaround |
|---|---|---|---|
| Blood panel | Cholestasis vs hepatocellular damage | ALP above 3 times the upper limit | 24 hours |
| Ultrasound | Duct width, wall, sludge, mass | Duct above 4 mm, wall above 1 mm | Same day, 2 to 4 hours |
| Bile cytology and culture | Bacteria, fluke eggs, neutrophils | Any growth, or 3+ bacteria per field | 3 to 5 days |
| Liver biopsy | Type, lymphoma, copper | Copper above 1,500 ppm dry weight | 5 to 10 days |
| Cobalamin | Gut involvement | Below the range on 2 draws | 24 hours |
Recheck schedule by type
Type 1: recheck bilirubin, ALP and GGT at 7 days, again at 4 weeks, and once more at 3 months. Fever that returns inside 72 hours means the antibiotic is wrong or a collection has formed.
Type 2: recheck at 4 weeks, then every 3 months for the first year, with a repeat ultrasound at 6 months. A cat that plateaus for 2 consecutive checks can move to every 6 months. Type 3: recheck at 6 weeks after treatment, then at 3 months; a repeat fecal sedimentation at 4 weeks tells you whether the fluke load dropped.
Emergency thresholds
Go now if the cat is jaundiced with a fever above 40 C, has a heart rate above 200 beats per minute, breathes more than 40 times a minute at rest, or has a temperature under 37.5 C with cold ears, which is sepsis until proven otherwise. A tense, painful abdomen within 24 hours of a bile sample means a leak. Head pressing, pacing, or a cat that does not recognise you points at hepatic encephalopathy and an ammonia problem; a head tilt or a cat that falls to one side is more often vestibular disease. Collapse, bleeding from the gums, or a bilirubin above 10 mg/dL all mean hospital, not a recheck.
Your next 7 days
- Ask for ALP, GGT, ALT, bilirubin, albumin, glucose and a CBC on day 1, not a liver panel alone, and price the workup with the cost calculator.
- Get a cobalamin level and a T4 at the same draw.
- Request an ultrasound report that states duct diameter in mm and wall thickness in mm.
- Before any bile sample, confirm platelets, clotting times and blood pressure in writing.
- Start a 7 day log of appetite, stool colour and jaundice in the gums, photographed in daylight.
Treatment follows the type and is prescription-only: antibiotics matched to a culture for type 1, immune suppression and bile acid support for type 2, and fluke treatment plus drainage for type 3. A cat that strains with an empty bladder is a separate emergency, covered under urinary blockage signs. What an owner controls is the timing of the 4 tests and the honesty of the recheck schedule.
Terms mentioned in this article
Frequently asked
Can ultrasound tell the 3 types apart?
Not reliably. Ultrasound measures duct width, wall thickness and sludge, and it can suggest obstruction or a mass, but neutrophilic, lymphocytic and fluke-related disease overlap on imaging. Bile cytology, culture and histology are what name the type.
How risky is a gallbladder sample?
It is the riskiest of the 4 tests because a bile leak causes peritonitis within hours. Platelets above 100,000, normal clotting times, controlled blood pressure, a 22 gauge needle and 1 pass keep the risk low. If the duct is obstructed, surgery is the safer route.
How often should a cat with cholangitis be rechecked?
Type 1 at 7 days, 4 weeks and 3 months. Type 2 at 4 weeks, then every 3 months for a year with an ultrasound at 6 months. Type 3 at 6 weeks and 3 months, with a repeat fecal sedimentation at 4 weeks.