Jaundice, Canine - contd.
The diagnosis of jaundice usually is based on the yellow discoloration of the skin or mucous membranes noted by the veterinarian upon physical examination. Bloodwork will document elevation of the serum bilirubin concentration, which in dogs is normally less than 1.0 mg/dl. Urinalysis will demonstrate an abnormal amount of bilirubin in the urine as well. Although elevated levels of bilirubin may be present in the blood and urine, jaundice may not become clinically evident until the serum bilirubin level reaches 2.0 mg/dl.
When jaundice is noted, additional tests will be needed to determine its cause. A complete blood count, or, at the very least, measurement of the packed cell volume, is typically done to rule out anemia. If anemia is present, then the jaundice may be due to red blood cell breakdown, a condition known as hemolysis, and additional tests will be needed to look for the cause of the anemia.
Jaundiced dogs that are not anemic most likely have liver or post-hepatic biliary tract disorders. A blood chemistry profile provides confirmation of elevated total serum bilirubin concentrations, and documentation of liver enzyme, serum electrolyte, and glucose levels and kidney function values. Urinalysis is important to confirm the presence of bilirubin in the urine. Small amounts of bilirubin can be found in the urine of many normal dogs, but large amounts are abnormal. Minor serum bilirubin elevations unaccompanied by jaundice or the presence of bilirubin in the urine may be incidental findings related to blood sample collection technique or recent ingestion of food, and therefore may not be significant.
Imaging studies provide important information in the diagnosis of hepatic and post-hepatic causes of jaundice. Abdominal radiographs, or x-rays, are routinely performed to assess liver size and to look for evidence of stones in the biliary tract. Abdominal ultrasound is the most readily available non-invasive diagnostic tool used to detect bile duct obstruction or primary gallbladder abnormalities not otherwise revealed by conventional radiographs. Ultrasound can also be used to guide needle biopsy of the liver. A liver biopsy provides tissue for microscopic detection of liver tissue abnormalities. This is typically done if anemia is not present and there is no evidence on ultrasound examination of bile duct obstruction or gallbladder disease. When the ultrasound study reveals obstruction, exploratory surgery is often necessary to identify and correct the obstruction's cause. Such surgery is also performed when a cause for the jaundice remains unclear after other diagnostic tests and procedures have been performed.
