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!
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