American Board of Internal Medicine (ABIM) Certification Practice Exam

What diagnostic method is used to confirm Wilson disease presenting as acute liver failure?

1. Blood tests for liver function

2. Urinary copper measurement

3. Liver biopsy

4. Genetic testing

The correct answer is: Urinary copper measurement

Urinary copper measurement is the primary diagnostic method used to confirm Wilson disease, especially in a case of acute liver failure. Wilson disease is a genetic disorder leading to an accumulation of copper in the body, primarily affecting the liver and brain. In cases of acute liver failure, urine copper levels become significantly elevated due to the inability of the liver to properly excrete copper. Measuring urinary copper is particularly useful because it reflects the body's copper metabolism and provides insight into excess copper excretion. Elevated urinary copper levels, especially when coupled with low serum ceruloplasmin and high free copper in the serum, can confirm the diagnosis of Wilson disease in the setting of acute liver failure. While blood tests for liver function can indicate liver damage, they do not provide specific information regarding the underlying cause, such as copper metabolism. Liver biopsy can also be performed to assess copper accumulation in liver tissue, but it is more invasive and not the first-line diagnostic approach in acute cases. Genetic testing for Wilson disease can identify specific mutations in the ATP7B gene, but it is not typically used to confirm acute presentations; rather, it serves as a supportive tool once Wilson disease is suspected. Thus, urinary copper measurement stands out as the most direct and effective method to