Bile Acid Test

Bile Acids and Liver Function

If your veterinarian suspects that your dog suffers from liver disease or a congenital liver defect, he or she is likely to order various lab tests to assist in making the diagnosis. One of these is a bile acid test.

While liver enzyme readings can indicate damage to liver cells, the bile acid test tells us how well the liver is functioning.

Here's How it is Supposed to Work

The liver produces bile acids that are stored in the gall bladder. These bile acids play a critical role in the digestion process, specifically the breakdown of fats. When your dog consumes a fat-containing meal, the enzyme lipase is released into the small intestine to split the complex lipid molecules into simple fatty acid and glycerol molecules.

There's only one problem: The lipase can't penetrate past the surface of the congealed fat globules.

This is where the bile acids come in.

The gall bladder contracts to secrete bile acids into the small intestine where they emulsify the fat molecules so they can be broken down into fatty acids and glycerol.

When the digestion process has been completed, the bile acids are absorbed from the intestines and transported back to the liver through the bloodstream.

If the liver is working correctly, it will "recycle” the bile acids by removing them from the bloodstream and sending them back to the gall bladder, where they remain until needed again.

What Does the Bile Acid Test Measure and How Is It Performed?

The bile acid test measures the ability of your dog's liver to "recycle" the bile acids by removing them from the bloodstream.

You will be asked to fast your dog for twelve hours prior to the test to give the liver ample time to retrieve circulating bile acids.

When your dog arrives at the vet's office, blood will be drawn. This is the pre-meal test. Your dog is then fed, and two hours later another blood sample is collected for the post-meal test.

If your dog's liver is functioning properly, the pre-meal test will show very low bile acid levels and the post-meal levels will be no more than slightly higher, as two hours should be adequate time for a healthy liver to recapture the bile acids. Moreover, in a healthy animal, the bile acids remain largely contained within the portal circulation system, that is, the localized blood flow between the liver and the intestines.

Elevated post- and/or pre-meal bile acid levels in the systemic blood supply are indicative of impaired liver function. The higher the level of bile acids circulating in the bloodstream, the greater the impairment typically is.

Bile Acid Tests in Liver Disease Diagnosis and Prognosis

While higher bile acid test results generally suggest greater liver impairment, they are not necessarily indicative of a poorer prognosis.

Dogs with congenital portosystemic shunts, for example, typically have extremely elevated bile acid levels, but this condition can be corrected with surgery in many cases.

With canine liver disease, the prognosis is greatly dependent on the root cause of the illness, and the bile acid test result by itself is not enough for a definitive diagnosis.

That said, when more than a minute amount of bile acids can be detected in the body's general blood circulation, this is a sure sign that liver function is impaired. Your veterinarian will likely recommend further tests to determine the cause and severity of the problem.

But what about the reverse?

Does a normal bile acid test result mean that your dog's liver is healthy?

Unfortunately not always, though it is safe to say that the dog would have to be in the very early stages of liver disease, or the problem would have to be mild and/or affect only a small part of the liver in order for the bile acid test to show no signs of liver impairment.

If your dog has elevated liver enzymes but normal bile acid levels and is asymptomatic, your veterinarian may suggest monitoring your dog's condition and retesting in 3-6 months, giving liver cells time to regenerate.

If, however, the elevated enzyme values are accompanied by symptoms indicative of liver disease, other diagnostic tests will probably be recommended.