Abnormal liver tests occur frequently. Liver enzymes are frequently confused with liver function tests. This module will help distinguish the two. It is important to be able to assess the test results in light of the patient’s presenting complaint, risk factors and condition. This module will also cover an approach to patients with abnormal liver test results.
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Gastroenterology – Abnormal Liver Tests
Whiteboard Animation Transcript
with Kelly Burak, MD
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INTRODUCTION
Liver tests or liver enzymes, sometimes incorrectly call liver “function” tests, refer to AST, ALT, ALP, and may include GGT. Abnormal values are often found on routine blood tests and indicate liver injury. Bilirubin, albumin and prothrombin time (or INR) are better tests of the function of the liver and are the LFTs.
How to Interpret Abnormal Liver Tests
A patient with abnormal liver tests can present in a number of different ways or can be completely asymptomatic.1,2,3 While a clinical assessment focused on risk factors and stigmata of liver disease remains key, the pattern of liver enzyme elevation will guide the differential and workup.
1. Take a look at which enzymes are elevated.
A rise in ALT and/or AST that is proportionally higher than ALP indicates a hepatocellular pattern of injury,1 while
A rise in ALP, confirmed to be from liver by an abnormal GGT, indicates a cholestatic pattern.1
2. What is the pattern?
If the pattern of injury is cholestatic – that is the ALP (and GGT) rise > ALT or AST – you will need to obtain a dedicated ultrasound of the liver and biliary tree to look at the bile ducts
Dilated bile duct indicate extrahepatic cholestasis and an ERCP may be needed for diagnosis and therapy
Normal bile ducts indicate intrahepatic cholestasis, and a liver biopsy may be required if the cause is not identified by history or other investigations, such as an anti-mitochondrial antibody or MRCP
If the pattern of injury is hepatocellular – that is the ALT or AST rise is greater than ALP (and GGT) – determine severity using the ALT level
An ALT of <300 is mild and 300-1000 correspond to moderate liver disease.1 These can be acute or chronic and unfortunately the differential diagnosis is broad
Non Alcoholic Fatty Liver Disease (NAFLD) is the most common cause of mild elevation4,5
Alcoholic liver disease is associated with an AST that is often 2-3 times higher than the ALT, but alcohol or NAFLD rarely cause the ALT to be <3001,4,5
Further evaluation and testing will be guided by your history and clinical suspicion
If ALT >1000 there is SEVERE liver injury which is always acute and symptomatic. These patients are at high risk of acute liver failure.1,3
If you see these values, think and test for the following: Drugs – especially acetaminophen overdose; Viruses – Hepatitis A through E, HSV, CMV, VZV; Ischemia from Budd-Chiari Syndrome or shock; Autoimmune Hepatitis; Wilson’s Disease; and if the patient is pregnant or recently postpartum, HELLP syndrome or acute fatty liver of pregnancy (AFLP)1,3
Quick recognition and diagnosis can guide appropriate management in these patients
