Case scenario: You are presented with a 2 year old Labrador retriever with a history of 3 seizures in the past 1 month. The seizures are consistent with generalized seizures and last less than 1 minute. Further questioning of the client reveals the dog to have normal activity, appetite, and mobility at home between seizures. You perform a neurologic examination (yay!) and no abnormalities are found.

What is the likelihood of idiopathic epilepsy in this dog?

According to the International Veterinary Epilepsy Task Force, a diagnosis of idiopathic epilepsy can be made, at a Tier I level of confidence, if a dog is between the ages of 6 months and 6 years, has had 2 or more seizures, has a normal interictal neurologic examination AND has normal CBC, serum biochemistry and dynamic bile acid testing (that means pre and post feeding testing). We know Labs are commonly diagnosed with idiopathic epilepsy and that a genetic inheritance is known or suspected for most of the breed. So, do we really need to do a bile acid test?

First, a little background. Minimum data base (MDB) pseudohepatic function tests include glucose, BUN, albumin, ALP and ALT. A pre-prandial bile acid test alone, called a resting bile acid test, is different than a dynamic bile acid test which includes both pre and postprandial samples.

Do we Reallllly Need to Perform Dynamic Bile Acid Testing?

An article from England recently addressed this question in a publication in the Veterinary Record (DOI: 10.1002/vetr.2585).

Questions asked:
1. If a dog has a normal MDB, how likely are we to finding an elevated postprandial bile acid test?" Answer: 24 dogs out of 202 dogs

2. How likely is a dog with a normal MDB and a normal pre-prandial bile acid test to have an elevated postprandial bile acid test? Answer: about 9 out of 100 dogs

3. What is the prevalence of a clinically significant hepatopathy in a dog with a normal MDB and normal pre-prandial serum bile acid test (if we don't do a post-prandial bile acid test)? Answer: 1.29%

The authors compared this to the risk of missing a significant brain lesion in a dog less than 6 years of age with a normal neurologic exam in which an MRI is not performed. (About 2.2% of cases would have had a brain lesion missed.) The question always begs, how much of a risk taker are you, or your client?

Based on the information from this study, here is what I propose we do:

ALWAYS check CBC, serum biochemistry for every dog with a history of 2 or more seizures.
ALWAYS recommend a pre AND post bile acid test for every dog presenting with a history of 2 or more seizures, even if CBC and serum biochemistry are normal. When making this recommendation I suggest that we make clients aware of the less than 2% chance that their dog could have a significant hepatopathy that will be undiagnosed if we do not perform these tests. This hepatopathy may be the reason for their seizures or, and perhaps more importantly, it could affect how they metabolize many of the anticonvulsants that we use. I'm looking at you phenobarbital, zonisamide and diazepam! Poor hepatic function could result in poor metabolism of these anticonvulsant drugs even if the hepatopathy isn't severe enough to be the seizure etiology.
ALWAYS perform a neurologic examination to document any abnormalities before starting any medications for seizures. (Okay, so this wasn't part of the study but I still think this is a must!)

Thanks for reading! This was a very informative article so check it out for more detail!

Have a seizure patient that you need a little backup for? Seizure management is my passion so I'd love to help! Email me or hop on my website to schedule a consult. Have a great week!

Hepatic encephalopathy is caused by changes in hepatic metabolism that result in neuronal damage or swelling. Clinical signs can include neurological, gastrointestinal or urinary due to the abnormal metabolites or the formation of stones. As a neurologist, I see these patients when they have seizures, changes in mentation or behavior, or other neurological signs.

The preferred treatment is surgical correction with slow closing of the offending vessel. As many of us know, this doesn't always correct all clinical signs and some dogs require life-long treatment despite successful surgical closure.
Life-long medical management must provide a high quality protein source, but yet remain a low protein diet to avoid excessive amino acids.

There was an interesting article published recently (https://onlinelibrary.wiley.com/doi/full/10.1111/jvim.16135?campaign=woletoc) that outlined the changes in the different types of amino acids present in the body. There are two main types of amino acids that researchers watch: branched chain amino acids (BCAA) and aromatic amino acids (AAA). In normal animals, the ratio of BCAA to AAA is 3.0 to 4.0, whereas it is 1.5 in animals with a portosystemic shunt. The study goals were to evaluate what happened with the amino acids after shunt surgery.

Results

Interestingly, specific BCAA and AAA did not change a lot, nor were they all outside of the reference range to start. However, the ratio of BCAA to AAA did increase (improve) but did not return back to the normal range. Clinical improvement was noted in most of the dogs, however!

What does this mean? It means that functional recovery occurs faster than biochemical recovery and functional recovery may be more "complete". This also (probably) means that we still need to dig into the amino acids a bit more to see if there are specific amino acids to be more or less worried about.

Yes, I know, this was a very academic TidBit this week and I promised they would be clinically applicable...I'm sorry! I do try to keep it clinically relevant but every now and again I must deep dive into research with you. :)

Keep those consults coming! This has been a terrific few weeks, with interesting cases. I love working with you and your staff to help patients.

Thanks for reading and have a great week!

Bile Acid Testing For Dogs with Seizures

Hepatic Encephalopathy - UPDATE