Jaundice is not a diagnosis and the cause should always be sought. The two most useful tests are the viral markers and an ultrasound examination. The liver biochemistry confirms the jaundice and may help in the diagnosis. Investigations include:
1 Viral markers for HAV and HBV (antibodies to ncv develop late).
2 An ultrasound should always be performed to exclude an extrahepatic obstruction unless the patient is young and the diagnosis of viral hepatitis is suspected. An ultrasound will demonstrate:
SIZE OF THE BILE DUCTS which are dilated in extrahepatic obstruction
LEVEL OF THE OBSTRUCTION
CAUSE OF THE OBSTRUCTION in virtually all tumours and in 75% of patients with gallstones The diagnosis of any mass lesion can be made by fineneedle aspiration cytology (sensitivity approximately 60%) or by needle biopsy using a spring-loaded device (sensitivity approximately 90%).
A flow diagram for the general investigation of the jaundiced patient is shown
In hepatitis the serum AST tends to be high early in the disease with only a small rise in the serum AP. Conversely, in extrahepatic obstruction the AP is high with a smaller rise in AST. These findings cannot, however, be relied on alone to make a diagnosis in an individual case. The PT is often prolonged in long-standing liver disease, and the serum albumin is also low.
These are helpful in a case of haemolytic jaundice. A raised white count may indicate infection, e.g. cholangitis. A leucopenia often occurs in viral hepatitis, while abnormal mononuclear cells suggest infectious mononucleosis and a Monospot test should be performed.
Other blood tests These include tests to exclude unusual causes of liver disease, e.g. cytomegalovirus antibodies, autoimmune antibodies, e.g. AMA for the diagnosis of primary biliary cirrhosis, and o-fetoprotein for a hepatocellular carcinoma.