From the Guidelines
The first imaging study to obtain for a patient with elevated liver enzymes is an abdominal ultrasound, as it is a non-invasive, readily available, and relatively inexpensive test that can evaluate the liver parenchyma, biliary system, and surrounding structures 1. This recommendation is based on the American College of Radiology's (ACR) Appropriateness Criteria for abnormal liver function tests, which suggests that ultrasound is usually appropriate as the initial imaging modality for patients with hepatocellular predominance and mild aminotransferase increase 1. The ACR criteria also note that ultrasound can be used in combination with other imaging modalities, such as CT or MRI, for patients with moderate or severe aminotransferase increase or cholestatic predominance 1. Ultrasound is particularly useful for detecting fatty liver disease, gallstones, biliary obstruction, liver masses, and hepatomegaly, which are common causes of liver enzyme elevation 1. Additionally, ultrasound can help identify both hepatocellular and cholestatic patterns of liver injury, which can guide further management decisions 1. If the ultrasound findings are inconclusive or additional information is needed, more advanced imaging such as CT, MRI, or MRCP may be subsequently ordered based on the clinical scenario and initial ultrasound results 1. It is essential to note that the choice of imaging modality may depend on the specific clinical scenario and the presence of underlying conditions, such as nonalcoholic fatty liver disease (NAFLD) or cirrhosis 1. In patients with suspected NAFLD, a stepwise approach using noninvasive tests, such as the Fibrosis 4 Index (FIB-4) and vibration-controlled elastography (VCTE), can be used to assess the risk of advanced hepatic fibrosis and guide further management 1.
From the Research
Initial Imaging Modality for Elevated Liver Enzymes
- The initial imaging modality for a patient with elevated liver enzymes is typically an abdominal ultrasound 2.
- Abdominal ultrasound is widely used for screening asymptomatic patients with an incidental elevation of liver enzymes, but it cannot detect small amounts of hepatic steatosis and cannot establish the diagnosis of nonalcoholic steatohepatitis (NASH) or stage of hepatic fibrosis 2.
- If non-invasive serologic studies remain inconclusive, ultrasound, mini-laparoscopy, and liver biopsy may help to establish the final diagnoses 3.
- Magnetic resonance cholangiopancreatography (MRCP) may be useful in patients with elevated liver enzyme levels, particularly those with inflammatory bowel disease, but it does not contribute markedly toward the evaluation of the cause of elevated enzyme levels in most patients 4.
- In patients with significantly elevated liver enzymes, a combination of serum biomarkers and radiologic modalities may provide the best diagnostic approach, and liver biopsy can be safely deferred in most patients 5.
Diagnostic Approach
- The diagnostic approach for patients with elevated liver enzymes typically involves repeating the test to confirm the result, followed by non-invasive serologic tests to differentiate between a predominant "necrotic pattern" and a predominant "cholestatic pattern" 3.
- The choice of initial imaging modality may depend on the clinical presentation and laboratory results, as well as the availability and expertise of the diagnostic modalities 6, 4.
Imaging Modalities
- Abdominal ultrasound is a commonly used initial imaging modality for patients with elevated liver enzymes due to its wide availability and non-invasive nature 2.
- MRCP may be used as a secondary imaging modality, particularly in patients with suspected biliary disease or inflammatory bowel disease 6, 4.
- Endoscopic ultrasound (EUS) may be used in certain cases, such as evaluating common bile duct dilatation, but its yield is low in patients with normal serum liver enzymes 6.