Abnormal Liver Function Tests

Introduction

Welcome to the QBankMD MCCQE1 preparation guide on Abnormal Liver Function Tests. This comprehensive resource is designed to help Canadian medical students excel in their MCCQE1 exam, focusing on the critical topic of liver function tests within the field of Hepatology.

Overview of Liver Function Tests

Liver function tests (LFTs) are a panel of blood tests that provide valuable information about the health and function of the liver. In Canadian medical practice, these tests are routinely used for diagnosis, monitoring, and management of various liver conditions.

Common Liver Function Tests

Interpretation of Abnormal Liver Function Tests

Understanding how to interpret abnormal LFTs is a key skill for the MCCQE1 exam. Let's break down the common patterns of liver enzyme abnormalities:

1. Hepatocellular Pattern

Characterized by predominant elevation of AST and ALT.

2. Cholestatic Pattern

Marked by predominant elevation of ALP and GGT.

3. Mixed Pattern

Shows features of both hepatocellular and cholestatic patterns.

Specific Abnormalities and Their Implications

Canadian Guidelines for Liver Function Test Interpretation

The Canadian Association for the Study of the Liver (CASL) provides guidelines for the interpretation and management of abnormal liver function tests. Key points include:

1. Initial evaluation should include a thorough history, physical examination, and review of medications and alcohol use.
2. Ultrasound is recommended as the first-line imaging modality for evaluating abnormal LFTs in Canada.
3. Referral to a hepatologist is recommended for persistent unexplained LFT abnormalities or evidence of advanced liver disease.

Key Points to Remember for MCCQE1

• Know the normal ranges for all liver function tests
• Understand the patterns of liver enzyme abnormalities (hepatocellular, cholestatic, mixed)
• Be familiar with common causes of abnormal LFTs in the Canadian population
• Recognize the importance of AST:ALT ratio in differentiating alcohol-related liver disease
• Understand the role of imaging studies, particularly ultrasound, in evaluating abnormal LFTs
• Be aware of when to refer patients to specialists according to Canadian guidelines
• Consider the impact of medications, including over-the-counter drugs, on LFTs
• Recognize the importance of LFTs in assessing liver disease severity and prognosis

Sample MCCQE1-Style Question

A 45-year-old man presents to his family physician in Toronto with fatigue and mild right upper quadrant discomfort for the past month. He has no significant medical history and takes no medications. He drinks 2-3 beers daily. Physical examination reveals mild hepatomegaly. Laboratory results show:

• ALT: 120 U/L (normal <40)
• AST: 80 U/L (normal <40)
• ALP: 110 U/L (normal <120)
• GGT: 75 U/L (normal <50)
• Total bilirubin: 25 μmol/L (normal <20)

Which one of the following is the most appropriate next step in management?

• A. Refer for liver biopsy
• B. Start ursodeoxycholic acid
• C. Order abdominal ultrasound
• D. Prescribe prednisone
• E. Recommend abstinence from alcohol and repeat LFTs in 4-6 weeks

Explanation

The correct answer is:

• E. Recommend abstinence from alcohol and repeat LFTs in 4-6 weeks

This patient presents with mildly elevated liver enzymes showing a predominantly hepatocellular pattern (ALT > AST). Given his alcohol consumption and the pattern of LFT abnormalities, alcohol-related liver disease is a likely diagnosis. In Canada, the first step in management for such cases is to recommend alcohol cessation and repeat the tests after a period of abstinence.

Option A (liver biopsy) is too invasive as a first step. Option B (ursodeoxycholic acid) is used primarily for cholestatic liver diseases. Option C (abdominal ultrasound) may be considered if LFTs remain abnormal after alcohol cessation. Option D (prednisone) is not indicated without a specific diagnosis requiring corticosteroid treatment.

This question tests the candidate's ability to interpret LFTs, recognize patterns of liver disease, and apply Canadian guidelines for initial management of suspected alcohol-related liver disease.

References

1. Canadian Association for the Study of the Liver. (2018). Clinical Practice Guidelines for the Management of Non-Alcoholic Fatty Liver Disease. Canadian Journal of Gastroenterology and Hepatology.

2. Friedman, L. S. (2021). Approach to the patient with abnormal liver biochemical and function tests. UpToDate. Retrieved from https://www.uptodate.com/contents/approach-to-the-patient-with-abnormal-liver-biochemical-and-function-tests (opens in a new tab)

3. Canadian Liver Foundation. (2022). Liver Disease in Canada: A Crisis in the Making. Retrieved from https://www.liver.ca/wp-content/uploads/2017/09/Liver-Disease-in-Canada-A-Crisis-in-the-Making.pdf (opens in a new tab)

4. Giannini, E. G., Testa, R., & Savarino, V. (2005). Liver enzyme alteration: a guide for clinicians. Canadian Medical Association Journal, 172(3), 367-379.

5. Statistics Canada. (2021). Heavy drinking, by sex, provinces and territories. Retrieved from https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=1310009610 (opens in a new tab)