The attending veterinarian will take a complete history from the dog’s owner and will perform a thorough physical examination. The initial data base usually will also include taking a blood sample for submission to a laboratory for a complete blood count and a serum biochemistry profile. The very first clue that a dog may have hepatitis is elevated liver enzymes in the blood. The serum chemistry panel is critical to identifying abnormal levels of circulating liver enzymes. A urine sample typically will also be taken and evaluated (a urinalysis). Abdominal radiographs (X-rays) may or may not be taken as part of the initial diagnostic work-up. Based on the results of these tests, more advanced diagnostics will probably be performed. These might include additional blood work to assess serum bile acid concentrations, plasma ammonia concentrations and blood coagulation function. Dogs with advanced chronic hepatitis usually have abnormal coagulation profiles, reflecting severe liver dysfunction.
Abdominal ultrasound is often quite useful to detect changes in the liver, especially in late-stage disease. A biopsy of the liver may be taken under ultrasound guidance. It can be taken through a process called laparoscopy, in which the veterinarian passes a sophisticated scope instrument through an incision in the body wall, enters the abdominal cavity and retracts tissue samples using the laparascope. A laparotomy can also be performed; this involves surgically opening the abdomen to take the sample directly. One advantage of this procedure is that it lets the veterinarian actually see most or all of the liver and to take multiple large samples from specific areas that look to be abnormal. A fine needle aspirate of liver tissue can also be taken, although this produces only a tiny sample and is not as reliable as the other methods. Regardless of the biopsy technique, the resulting tissue samples will be submitted to a pathology laboratory for microscopic evaluation through a process called histopathology. The samples can also be cultured, which is a process that uses special growth media to see whether microorganisms grow from the tissue.
Unexplained, abnormally elevated circulating liver enzyme levels usually are the very first evidence of liver disease, even in the very early stages. This is one of many reasons that it may be sensible to conduct routine baseline blood work from time to time, even if a dog is not showing any signs of illness. This is especially important as a dog advances in age.
Dogs with moderate to advanced liver disease are anesthetic risks. Many drugs used to induce or maintain anesthesia are metabolized by the liver; when it is damaged or failing, it cannot process those drugs properly.