Review Question - QID 104607

In this patient with a conjugated hyperbilirubinemia and elevated alkaline phosphatase, a right upper quadrant ultrasound is the diagnostic modality of choice in distinguishing between intra- and extrahepatic biliary obstruction.

This woman's symptoms and laboratory results are consistent with biliary obstruction. Next, a right upper quadrant ultrasound is used to determine where this obstruction may lie. Ultrasound can be diagnostic for one of the major extrahepatic causes of obstruction: choledocholithiasis. This woman's history of scleroderma raises concern for the possibility of primary biliary cirrhosis (PBC), an intrahepatic cause of biliary obstruction that typically presents in middle-aged women. Fatigue and pruritus are common initial complaints, while jaundice is usually a later finding.

Roche and Kobos review the differential diagnosis for jaundice in the adult patient. In addition to PBC, another serious autoimmune disease that affects the biliary system is primary sclerosing cholangitis (PSC). Primary sclerosing cholangitis is also a rare disease and is more common in men. There is a strong association with inflammatory bowel disease.

Lindor et al. present practice guidelines for PBC. The authors, in describing the pathophysiology of the disease, note the high degree of specificity for the small intrahepatic bile ducts. They also remark on the utility of the anti-mitochondrial antibody (AMA) in confirming the diagnosis of PBC. The AMA is highly specific and is found in 90-95% of individuals with PBC and less than 1% of the general population.

Illustration A is an ultrasound of a patient with intrahepatic biliary obstruction. Note the diffusely dilated bile ducts throughout the liver parenchyma. This would be seen in isolation in the setting of PBC, but may be seen in addition to dilation of the extrahepatic biliary tree in choledocolithiasis.

Incorrect Answers:
Answer 1: If one has strong suspicion for PBC, several antibody tests can be useful including AMA (anti-mitochondrial antibodies), antinuclear (ANA) antibodies, and anti-smooth muscle (ASMA) antibodies. However, one must first determine if there is evidence of biliary obstruction and where the obstruction is located, using ultrasound.
Answer 3: A blood smear can be useful in patients with hyperbilirubinemia due to hemolysis. These patients have an unconjugated hyperbilirubinemia.
Answer 4: A CT may be helpful in diagnosing an obstructive malignancy, but is generally reserved for use after the right upper quadrant ultrasound.
Answer 5: A biopsy is ultimately necessary for the diagnosis of PBC. However, one must first determine if there is evidence of biliary obstruction on imaging and where the obstruction is located.