What are the steps for a standard ultrasound liver scan protocol?

Liver Ultrasound Scanning Protocol

A standardized, systematic approach to liver ultrasound should be followed every time to ensure complete examination and minimize missed findings, beginning with proper patient preparation and proceeding through sequential anatomical assessment. 1, 2

Pre-Procedure Preparation

• Ensure the patient has fasted for at least 3 hours before the examination, particularly if liver stiffness measurements or elastography will be performed, as meal ingestion falsely elevates liver stiffness values and leads to overestimation of fibrosis. 1

• For basic liver ultrasound without elastography, no specific preparation beyond the fasting consideration is required. 1

• Review any recent liver imaging obtained within the past 3 months before beginning the scan to identify anatomical variations, focal lesions, or potential contraindications. 1

Equipment Setup and Transducer Selection

• Select the appropriate transducer based on patient body habitus and the specific examination goals—this is critical for optimal image acquisition. 2

• Adjust equipment settings including gain, depth, and focal zones before beginning the systematic scan. 2

Systematic Scanning Approach

Use a structured, standardized scanning technique every time to develop pattern recognition and ensure completeness. 2

• Begin with a comprehensive survey of the entire liver in multiple planes (longitudinal, transverse, and oblique views). 2

• Systematically evaluate and document the gallbladder as part of every liver examination. 1

• Assess the liver parenchyma for echogenicity, focal lesions, and architectural distortion. 3

• Evaluate major vascular structures including the portal vein, hepatic veins, and hepatic artery. 2

• Document the liver size and contour, noting any nodularity suggestive of cirrhosis. 3

Assessment of Specific Liver Conditions

Fatty Liver Evaluation

• Use a 5-parameter scoring system that includes liver-to-kidney contrast and vessel wall clarity to improve diagnostic performance for steatosis. 1

• Recognize that ultrasound has limited sensitivity for detecting steatosis below 12.5% liver fat content. 1

Focal Lesion Detection

• When focal lesions are identified, document their size, location, echogenicity, and relationship to vascular structures. 4

• Ultrasound guidance should be used whenever possible when targeting focal lesions to minimize complications and improve diagnostic yield. 1

Advanced Techniques for Fibrosis Assessment

• Vibration-controlled transient elastography (TE) is the most widely validated method for assessing liver fibrosis or cirrhosis. 1

• Point shear wave elastography (pSWE) or 2D shear wave elastography (2D-SWE) serve as alternative methods when TE is not available. 1

• Acoustic radiation force impulse (ARFI) is particularly useful in patients with obesity, ascites, or nonalcoholic fatty liver disease. 1

• Apply the vendor-neutral "rule of four" for interpretation of ARFI techniques to simplify results and improve clinical relevance. 5

Surveillance Protocols

• 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

• Ultrasound with or without alpha-fetoprotein is the recommended imaging modality for hepatoma surveillance based on cost-effectiveness and historical evidence of impact on outcomes. 6

Critical Pitfalls to Avoid

• Never perform elastography or stiffness measurements within 3 hours of meal ingestion, as this causes falsely elevated values that overestimate fibrosis stage. 1

• Recognize that ultrasound cannot adequately discriminate between adjacent fibrosis stages and has inherent limitations. 1

• In morbidly obese patients, those with significant ascites, or nodular cirrhotic livers, image quality may be suboptimal—consider alternative imaging with CT or MRI in these cases. 1, 4

• Do not rely solely on ultrasound findings for definitive diagnosis of malignant lesions; consider the full differential diagnosis and use additional imaging modalities when indicated. 4

• When ultrasound provides inadequate visualization of liver parenchyma or reveals indeterminate lesions, pursue alternate imaging modalities such as contrast-enhanced CT or MRI rather than accepting an incomplete examination. 6