What is the recommended liver scanning protocol for ultrasound in radiology?

Liver Ultrasound Scanning Protocol

Pre-Procedure Preparation

For standard liver ultrasound, no specific patient preparation is required, but if elastography or liver stiffness measurements are planned, ensure the patient has fasted for a minimum of 3 hours, as meal ingestion falsely elevates stiffness values and overestimates fibrosis. 1

• Review any recent liver imaging obtained within the past 3 months before beginning the examination to identify anatomical variations, focal lesions, or contraindications that may affect your scanning approach 1

Equipment Selection

• Use a general-purpose curved array abdominal probe with a frequency range of 2-5 MHz for standard liver assessment 2
• Higher frequency probes may be used for superficial structures when image quality permits 2

Systematic Scanning Technique

Scan the liver systematically in real-time through all tissue planes in at least two orthogonal directions to ensure complete evaluation. 2

Subcostal Approach

• Place the probe high in the epigastrium and sweep laterally while holding it immediately adjacent to the costal margin 2
• For mid-clavicular line measurements, maintain the liver margin within the field of view and have the patient take and hold a deep breath to improve visualization 2

Intercostal Approach

• When the liver margin cannot be visualized below the costal margin, use an intercostal approach with the transducer oriented parallel to the ribs and the indicator directed toward the vertebral end of the rib 2
• Scan the entire extent of the organ in real-time in both long and short axes to avoid confusing the liver with fluid-filled tubular structures 2

Mandatory Anatomical Structures to Document

• Systematically evaluate and document the gallbladder in every liver ultrasound examination 1
• Assess liver size, contour, and echogenicity in multiple planes 1
• Evaluate the portal vein, hepatic veins, and hepatic artery using grayscale and Doppler imaging 3

Fatty Liver Assessment

When evaluating for hepatic steatosis:

• Use liver-to-kidney contrast as one parameter in a 5-parameter scoring system to improve diagnostic performance 1
• Assess vessel wall clarity as part of the scoring system 1
• Recognize that ultrasound has limited sensitivity for detecting steatosis below 12.5% liver fat content and cannot adequately discriminate between adjacent fibrosis stages 1

Focal Lesion Evaluation

When a focal lesion is identified:

• For lesions ≥1 cm, proceed to multiphasic contrast-enhanced CT or MRI as first-line imaging for definitive characterization 4
• Lesions between 1-2 cm require evaluation with two different imaging modalities showing classic arterial enhancement for non-invasive HCC diagnosis 3
• Lesions >2 cm require only one imaging modality showing classic arterial enhancement for HCC diagnosis 3
• Lesions <1 cm should be re-evaluated with triphasic CT, MRI, or contrast-enhanced ultrasound every 3-4 months, with enlarging lesions managed according to size-based protocols 3

Advanced Elastography Techniques

For fibrosis assessment:

• Vibration-controlled transient elastography (TE) is the most widely validated method for assessing fibrosis or cirrhosis 1
• Point shear wave elastography (pSWE) or 2D shear wave elastography (2D-SWE) serve as alternative methods 1
• Acoustic radiation force impulse (ARFI) is particularly useful in patients with obesity, ascites, or nonalcoholic fatty liver disease 1

Surveillance Protocols for High-Risk Patients

For patients with cirrhosis or chronic hepatitis B with risk factors, perform ultrasound examination every 6 months as the standard surveillance interval for hepatocellular carcinoma screening. 1, 4

• The combined use of ultrasound with alpha-fetoprotein (AFP) testing increases sensitivity while decreasing specificity and represents a reasonable option 4
• Ultrasound is the surveillance modality recommended by international guidelines in nearly all circumstances 3

Critical Pitfalls to Avoid

• Do not rely on ultrasound alone in patients with severe obesity, significant steatosis, or nodular cirrhotic livers—these patients require alternative imaging with multiphase CT or MRI for adequate assessment 3, 1
• Never perform elastography or stiffness measurements within 3 hours of meal ingestion, as this produces falsely elevated values 1
• Grayscale ultrasound and Doppler can diagnose cirrhosis but do so unreliably using morphologic features and cannot diagnose earlier, treatable stages of hepatic fibrosis 3
• Ultrasound is particularly limited for identifying hepatocellular carcinoma in patients with obesity, nonalcoholic fatty liver disease, and nodular cirrhotic livers—consider screening these patients with MRI or multiphase CT instead 3
• Use ultrasound guidance whenever possible when targeting focal lesions to minimize complications and improve diagnostic yield 1