Bile acids in cats and dogs

What it shows

Bile acids circulate in a loop: liver, bile, gut, portal vein and back to the liver. More than 90% are reabsorbed in the gut, and liver cells extract over 95% of what arrives in the portal blood (eClinPath), so very little remains in the general circulation. A meal makes the gallbladder contract and sends a wave of bile acids around this loop — a natural workload test for the liver.

That is why the test is usually a pair: one sample before a meal and another 2 hours after it. A healthy liver keeps both values low, the second only slightly higher. The test shows whether the liver copes with its workload, not the cause, severity or reversibility of a problem (VCA).

Higher than reference — what it may be a sign of

• Reduced liver function: loss of working liver cells, which can neither produce nor recapture bile acids properly.
• Blood bypassing the liver: a portosystemic shunt, or portal vein hypoplasia (formerly called microvascular dysplasia) in small dog breeds. With a shunt the after-meal value is usually markedly high, while the before-meal value may be in range (Merck).
• Bile flow problems: when bile cannot drain, bile acids flow back into the blood.
• Outside the liver: Cushing’s disease in dogs can raise them. If your pet gets ursodeoxycholic acid, a bile acid medicine, tell the vet: it raises the result (Merck).
• Sample: lipemia can falsely raise the result (eClinPath).

Lower than reference

Low values are expected in health, but some conditions make the test less sensitive: very long fasting, poor absorption in the gut, rapid passage through the gut, slow emptying of the stomach, or a gallbladder that does not contract well. Hemolysis falsely lowers the result. In about 15–20% of dogs and 5–10% of cats the before-meal value is higher than the after-meal one (Merck); this alone is not a problem, and the higher of the two values is the one that is read (eClinPath).

Look at together with

• ALT, ALP, GGT — abnormally high liver enzymes are a common reason to order bile acids (VCA).
• Albumin, glucose, urea, cholesterol — substances the liver makes; a severe loss of liver function may lower them (VCA).
• Bilirubin — when jaundice is not caused by hemolysis, bile acids are redundant: they are already high (Merck).
• Ammonia, ultrasound, biopsy — possible next steps when a shunt or liver disease is suspected.

Units and conversion

Bile acids are reported in µmol/L, on Russian forms мкмоль/л; these are the same unit, and no conversion is needed. Forms usually list two results — before and after the meal, sometimes labelled fasting and postprandial. Each result is read on its own; they are not added together.

Reference range

The reference range is on your lab’s form, often separately for the two samples. The Merck Veterinary Manual considers a value above 25 µmol/L in dogs or above 20 µmol/L in cats, in either sample, as abnormal; eClinPath gives similar cut-offs. The result depends on the protocol: fasting before the first sample, the meal and exact timing of the second sample all matter. VCA advises a 12-hour fast, while Merck notes that fasting is not required — follow your clinic’s instructions. A normal result does not rule out mild or localised liver disease.

Cats and dogs

Sources

1. eClinPath (Cornell University) — Bile acids
2. Hepatic Function Tests in Small Animals. Merck Veterinary Manual
3. VCA Animal Hospitals — Bile Acid Test
4. VCA Animal Hospitals — Testing for Liver Disease
5. Clinical Biochemistry. Merck Veterinary Manual