US Screening for HCC in Cirrhosis: US LI-RADS v2024 ACR
Why the US LI-RADS Algorithm Changed
The ACR US LI-RADS Surveillance v2024 updated the previous ultrasound surveillance algorithm for high-risk HCC patients. The practical purpose of the update is to distinguish 'no lesion' from 'lesion might not have been visible' and to consider AFP as an independent trigger for diagnostic imaging.
For the ultrasound diagnostician, this means the screening protocol must include not only the US-1/US-2/US-3 category but also a visualization score, and if available, the AFP result. The final recommendation is formed at the patient level, not just based on the detected nodule.
Who US LI-RADS Surveillance Applies To
The algorithm is intended for ultrasound screening of hepatocellular carcinoma in adult patients at high risk, primarily with liver cirrhosis. It is not a definitive diagnostic system for HCC: a positive screening routes the patient to diagnostic contrast imaging, where appropriate LI-RADS diagnostic algorithms are applied.
In the screening report, it is important not to replace the category with the descriptive phrase 'no focal changes.' For clinical decision-making, three elements are needed: US category, visualization score, and in version v2024, AFP status.
Categories US-1, US-2, US-3 and Strategy
| Screening Situation | Category | v2024 Threshold | Typical Strategy |
|---|---|---|---|
| No observable lesions or only definitely benign findings | US-1 Negative | No suspicious lesion | With negative AFP and VIS-A/VIS-B — scheduled surveillance in 6 months |
| Lesion does not appear definitely benign but is too small for positive screening | US-2 Subthreshold | <10 mm | Short interval: repeat ultrasound in 3–6 months if no positive AFP and significant visualization limitations |
| Lesion does not appear definitely benign | US-3 Positive | ≥10 mm | Diagnostic multiphase CT or MRI with contrast; diagnostic CEUS may be used in appropriate context |
| New thrombus in a vein suspicious for tumor | US-3 Positive | Qualitative feature | Diagnostic contrast imaging without waiting for scheduled interval |
| Positive AFP with non-positive ultrasound | Positive screening at the patient level | AFP ≥20 ng/mL | Diagnostic contrast imaging, even if ultrasound category is US-1 or US-2 |
AFP in Version 2024: What Changes in the Report
The main numerical update for routing is the AFP threshold ≥20 ng/mL. In v2024, a positive AFP makes the screening positive at the patient level, even when ultrasound does not reveal a lesion ≥10 mm.
This is especially important in cirrhosis with nodular transformation, obesity, steatosis, or deep right lobe: absence of a visible lesion on ultrasound does not exclude early HCC. Therefore, it is advisable to explicitly state in the protocol: 'AFP not provided,' 'AFP negative,' or 'AFP positive' if the laboratory result is available at the time of interpretation.
Visualization Score: A, B, C
The visualization score describes the expected sensitivity of ultrasound for a specific patient. It is not an assessment of the physician's work quality but a clinical marker of how reliably this ultrasound is suitable for screening small lesions.
| VIS | Meaning | Clinical Significance |
|---|---|---|
| VIS-A | No or minimal limitations | Ultrasound is suitable for standard 6-month surveillance with a negative result |
| VIS-B | Moderate limitations | Small lesions may be less noticeable, but the study usually remains applicable for screening |
| VIS-C | Significant limitations | Ultrasound sensitivity is significantly reduced; alternative routing is required with non-positive ultrasound |
Typical reasons for VIS-C include significant ultrasound attenuation, coarse parenchymal heterogeneity, unfavorable body habitus, limited visualization of the dome and deep liver sections. It is important not to 'understate' VIS-C out of fear of excessive studies: this score informs the clinician that a negative ultrasound screening is not sufficiently reliable.
VIS-C with US-1 or US-2: Why This Is Not a Routine Negative Result
In the v2024 update, VIS-C affects the patient's pathway with non-positive ultrasound. If US-1 or US-2 category is obtained with significantly limited visualization, the conclusion should emphasize the low reliability of ultrasound screening. In such a situation, routing to an alternative observation method, often MRI or CT with contrast, is advisable, considering the clinical context and method availability.
A practical formulation might be: 'US-1, VIS-C: no lesions corresponding to positive ultrasound screening detected; significant visualization limitations reduce study sensitivity. Recommend alternative imaging according to ACR US LI-RADS v2024.'
How to Describe Lesions Less Than 10 mm
A lesion <10 mm that is not definitely benign is classified as US-2. This category is designed to reduce the number of immediate CT/MRI for very small nonspecific findings, but it does not mean 'normal.' The recommended follow-up interval is 3–6 months.
The description should include localization, size in millimeters, echogenicity, contours, presence or absence of Doppler signal, comparison with previous studies. If such a lesion persists, increases, or reaches 10 mm, further strategy shifts towards positive screening and diagnostic contrast imaging.
When Immediate Diagnostic CT or MRI Is Needed
Immediate diagnostic routing is indicated for US-3: a lesion ≥10 mm that is not definitely benign, or a new suspicious thrombus in a vein. According to v2024, the same principle applies with positive AFP ≥20 ng/mL, even if the ultrasound picture is non-positive.
The task of the ultrasound specialist is not to make a final HCC diagnosis based on grayscale screening but to correctly include the patient in the next diagnostic stage. The conclusion should not state 'probable HCC' without sufficient grounds; it is better to use the standardized category US-3 Positive and direct recommendation for diagnostic multiphase imaging.
Minimum Report Template
- Indication: HCC screening in a high-risk patient, e.g., cirrhosis.
- Liver: echostructure, signs of cirrhosis, technical limitations.
- Findings: none; definitely benign; lesion <10 mm; lesion ≥10 mm; suspicious venous thrombus.
- US category: US-1 Negative, US-2 Subthreshold, or US-3 Positive.
- Visualization score: VIS-A, VIS-B, or VIS-C.
- AFP: negative, positive ≥20 ng/mL, or not provided.
- Recommendation: 6 months, 3–6 months, diagnostic CT/MRI/CEUS, or alternative imaging with VIS-C.
Common Implementation Errors
The first error is not indicating VIS. Without it, the clinician does not understand how reliable the negative result is. The second is considering US-2 'positive' and automatically referring all patients with subcentimeter lesions for CT/MRI; v2024 maintains a short ultrasound follow-up of 3–6 months if there are no other triggers. The third is ignoring AFP: a value ≥20 ng/mL changes the patient's pathway even with US-1.
The optimal protocol is short but structured: category, VIS, AFP, and action. This form makes US LI-RADS v2024 a working tool for monitoring patients with cirrhosis and reduces the risk of missing HCC behind the phrase 'no focal lesions detected.'
Frequently asked questions
If the ultrasound is negative but AFP is 25 ng/mL, what is the category?
Based on US findings, it could be US-1 or US-2, but screening at the patient level is considered positive due to AFP ≥20 ng/mL. Diagnostic contrast CT or MRI is needed.
How does US-2 differ from US-3?
US-2 is a lesion not definitely benign <10 mm; usually, follow-up ultrasound in 3–6 months. US-3 is a lesion ≥10 mm or a new suspicious venous thrombus; diagnostic contrast imaging is required.
What to do with US-1 but VIS-C?
US-1 means no positive finding was detected, but VIS-C indicates significantly limited ultrasound sensitivity. In v2024, such a result requires alternative routing, usually MRI or CT, rather than a simple routine repeat of a poor ultrasound.