Chronic Active Hepatitis (CAH) in Dogs
Dr. Bari Spielman
The clinical signs associated with CAH are rather vague and nonspecific, so your veterinarian may not be able to make a presumptive diagnosis without performing certain diagnostic tests. A complete history and thorough physical examination are important initial steps to take. The following tests are then considered to rule out other disorders and to confirm a diagnosis of CAH: A complete blood count (CBC) may be within normal limits. It may also reveal a mild anemia, an elevation in white blood cell count, and a low circulation protein level.
A biochemical profile usually reveals elevations in liver enzymes. Other abnormalities may be seen, such as an elevated bilirubin (evidence of jaundice), low circulating proteins, low blood sugar, low blood urea nitrogen, and low cholesterol. Electrolyte abnormalities such as low potassium, low chloride and high sodium levels are also common.
A urinalysis helps assess the kidneys and level of hydration of the patient and may sometimes detect bilirubin in the urine.
Serum bile acids are usually elevated, which denotes an inability of the liver to function normally. Measurement of bile acids may be performed in patients who have normal bilirubin levels.
A clotting profile, as clotting disorders are common with chronic liver disease. In addition, biopsies of the liver become more dangerous if the blood cannot clot properly.
Blood tests to detect abnormal ammonia levels in the blood may be useful, particularly if the animal is depressed, disoriented, and has seizures or other signs of hepatic encephalopathy.
Abdominal radiographs (X-rays) may be within normal limits, although they may reveal fluid in the abdomen (ascites), enlarged liver (hepatomegaly) or small liver (microhepatica).
Abdominal ultrasonography is recommended in most cases. It is very helpful in evaluating all of the abdominal organs, including the liver. It is equally important to rule out other disorders or diseases that may initially be difficult to differentiate from CAH. With the guidance of ultrasound, it is often possible to obtain a sample of the liver for evaluation and culture/sensitivity. A clotting profile should be performed first, and tissue should only obtained if the clotting parameters are within normal limits. Your veterinarian may refer your dog to a specialist in veterinary internal medicine or veterinary radiology to perform this procedure.
Your veterinarian may recommend additional tests to exclude or diagnose concurrent conditions and to confirm the diagnosis of CAH. These tests are not necessary in every dog, so are selected on a case-by-case basis:
Laparoscopy is a procedure that allows visualization and sampling of abdominal structures via a small scope introduced into the abdomen through a tiny incision. It is more invasive than an ultrasound-guided biopsy, but it allows the veterinarian to look directly at the liver and its associated structures. It helps ensure that the biopsy is taken from an area of the liver that is clearly abnormal. It requires that the animal be placed under general anesthesia, and usually requires referral of the animal to a veterinary facility with the appropriate specialized instruments.
Laparotomy is an abdominal exploratory surgery. It allows close inspection of the entire liver and other abdominal structures. It allows large biopsy samples to be obtained and may be indicated in cases where an biliary obstruction needs to be relieved and diverted. It also provides a mechanism for the removal of certain masses and tumors that may be responsible for the clinical signs.