At first glance, you might think this blog is a do it yourself piece on performing a biopsy. Not so fast. Veterinarians at the Animal Medical Center have at their disposal a wide array of medical equipment designed to collect a sample from your pet’s liver to determine the underlying cause of an abnormal liver. As your pet’s voice, the ultimate decision on the type of biopsy performed is yours; although your veterinarian will make a recommendation based on a full medical evaluation of your pet. This blog is composed to help you understand the methods for liver biopsy available to dogs and cats, as well as the pros and cons of each.
The Need for a Liver Biopsy
The recommendation for a liver biopsy typically comes after a full medical evaluation, which includes bloodwork, an ultrasound and often infectious disease testing. Sometimes, the liver is abnormal because of a systemic infection like leptospirosis, but that type of diagnosis can be made by testing for the presence of the infectious agent. Liver blood tests may be abnormal if there is a shunting liver blood vessel, but a liver shunt is commonly diagnosed with a special blood test called bile acids. In canine Cushing’s disease, the liver blood tests are frequently elevated, but other abnormalities discovered during a medical evaluation like hair loss, excessive drinking, and panting, clues your veterinarian into a diagnosis of Cushing’s disease. At AMC we can obtain samples from the liver via fine needle aspiration, percutaneous biopsy, laparoscopic biopsy, and exploratory laparotomy. Your veterinarian may not have as many options for obtaining a liver as we do at AMC, but every veterinarian will employ some of these liver biopsy methods.
Fine Needle Aspiration
This is the simplest and fastest method of sampling the liver. The pet is sedated lightly, then, using ultrasound guidance, a needle similar to one used for vaccination is inserted into the liver and cells are removed using the suction from a syringe. Only a few drops of cells are obtained, and they are squirted onto a microscope slide. In the laboratory, the cells are specially stained and a clinical pathologist examines the slide using a microscope and issues a report with their findings. The down side of this type of liver test is the small sample size.
Percutaneous Liver Biopsy
This biopsy method is similar to a fine needle aspiration since it requires only sedation and uses ultrasound guidance. But, percutaneous liver biopsy requires a larger, more specialized needle to get a sample of liver. The needle obtains a sample of the liver about one inch long and the width of a piece of angel hair pasta. Obviously, the sample is not very big and since the procedure occurs through the skin, it is more difficult to monitor for hemorrhage following the biopsy.
Laparoscopic Liver Biopsy
Laparoscopy is a minimally invasive method of obtaining a liver biopsy. Highly specialized equipment and expert training are required to perform this type of biopsy. Because the surgeon can see the biopsy site using the laparoscopic cameras, they can choose a representative area of the liver for biopsy and can easily monitor for bleeding. Pathologists like liver biopsies obtained via laparoscopy since the samples are about the size of a piece of Chicklet gum.
Liver Biopsy via Exploratory Laparotomy
For years, this was the only method of liver biopsy and if multiple organs are affected by the disease process, an exploratory surgery is a very efficient method to biopsy the liver as well as other abnormal abdominal organs. Like the laparoscopic liver biopsy, an exploratory laparotomy allows the surgeon to see all the abdominal organs and take adequate sized biopsies for pathologic evaluation. But, it is an abdominal surgery and most veterinarians will avoid this procedure if only a liver biopsy is necessary.
Choosing the Best for Your Pet
For most patients, we would want a larger rather than a smaller biopsy sample and thus veterinarians prefer laparoscopic liver biopsies over percutaneous liver biopsies. The larger sample helps the pathologist see if the abnormalities are a consistent finding throughout the liver or if different regions of the liver have different abnormalities. If the ultrasound shows only a single abnormal area, for example, a tumor, we might recommend an exploratory laparotomy. This procedure gives the surgeon the opportunity to not only biopsy the tumor, but to remove it as well in a single procedure. Because fine needle aspiration collects only cells, it is best when the working diagnosis is cancer. Malignant cells can be very easily identified by their abnormal appearance when viewed under the microscope. Aspiration cytology is less accurate if the working diagnosis is inflammation.
I hope your pet is never so sick as to need a liver biopsy, but if she does, you now have all the information necessary to make the best decision possible.