REBOOT #293 The Best of Liver Tests with Dr. Elliot Tapper
Sep 4, 2023
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Dr. Elliot Tapper, liver expert, walks us through the best of liver tests. He discusses targeted labs for differentiating hepatocellular versus cholestatic injury, addresses isolated lab abnormalities, and reviews causes of severe acute liver disease and issues in pregnancy. Listen and learn what 'liver function tests' really mean!
Differentiating hepatocellular and cholestatic liver injury using ALT, AST, and ALP levels is crucial.
For hepatocellular injury, ruling out drug-induced liver injury and checking for acute viral hepatitis is recommended.
Differentiation between direct and indirect hyperbilirubinemia is important when evaluating chronic elevations in total bilirubin.
Deep dives
Differentiating hepatocellular injury from colostatic injury
To determine the type of liver injury, it is important to consider the levels of ALT, AST, and alkaline phosphatase (ALP). An ALT and AST that are several-fold higher than the upper limit of normal, along with a slightly elevated ALP, indicate hepatocellular injury. On the other hand, if the ALP is significantly elevated and the ALT and AST are only mildly elevated, it suggests colostatic injury. Additionally, using the R score (ALT divided by ALP), a value greater than five suggests hepatocellular injury.
Considering drug-induced liver injury as a potential cause
In cases of hepatocellular injury, it is important to rule out drug-induced liver injury. Checking for acute viral hepatitis (Hep B, Hep C, Hep A) is also recommended. If there is suspicion of bile duct obstruction, imaging such as ultrasound or MRCP may be necessary. For patients with isolated elevated ALP, monitoring over time may be sufficient, especially if symptoms are absent. However, if symptoms of itching and fatigue are present, further evaluation and testing for conditions like primary biliary cholangitis may be warranted.
Evaluating isolated hyperbilirubinemia and indirect hyperbilirubinemia
For patients with chronic elevations in total bilirubin, it is important to differentiate between direct and indirect hyperbilirubinemia. If the bilirubin is predominantly direct, further evaluation for conditions like drug-induced liver injury and primary biliary cholangitis may be necessary. On the other hand, if the bilirubin is predominantly indirect, causes such as Gilbert's syndrome and hemolysis should be considered. In cases of isolated hyperbilirubinemia without symptoms, repeating the bilirubin level and assessing factors like fasting, lack of sleep, and smoking can provide more insights.
Differential Diagnosis for Elevated Liver Enzymes
When evaluating elevated liver enzymes, it is important to consider different patterns of injury, such as hepatocellular, cholestatic, or mixed. Possible etiologies for severe hepatocellular injury include viral hepatitis, autoimmune hepatitis, drug-induced liver injury, and ischemic hepatitis. Additional tests, such as ANA and smooth muscle antibody, can help in diagnosing autoimmune hepatitis. Imaging tests, like ultrasound, can be useful for further evaluation.
Acute Liver Failure and Etiologies
Acute liver failure is characterized by severe acute liver injury, along with coagulopathy and hepatic encephalopathy. The most common etiologies of acute liver failure in the United States are drug-induced, particularly from acetaminophen toxicity, followed by viral hepatitis and other less common causes. Recognition of severe liver injury and prompt intervention are essential in managing acute liver failure.
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Take a walk through Liver Land with Dr. Elliot Tapper (@ebtapper on Twitter) as we stroll through the best of liver tests. Once differentiating a hepatocellular versus cholestatic injury picture, Dr. Tapper shares some targeted labs to help with etiology, as well as what to do with those pesky isolated lab abnormalities. On top of that, we review common causes of severe acute liver disease and issues in pregnancy. Join us, and you’ll be writing more accurate notes as Dr. Tapper schools us on what “liver function tests” really mean!
Cover Art and Infographic: Kate Grant MD; Elena Gibson MD
Hosts: Stuart Brigham MD; Matthew Watto MD, FACP; Paul Williams MD, FACP
Editor: Emi Okamoto MD (written materials); Clair Morgan of nodderly.com
Guest: Elliot Tapper MD
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Show Segments
Intro, disclaimer, guest bio
Guest one-liner
Definitions of liver enzymes, liver function tests
Patterns of acute liver injury
Drug-induced liver injury
Isolated alkaline phosphatase elevation
Isolated total bilirubin elevation
Livery Injury During Pregnancy
Acute liver failure
Outro
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