HCC within LR-M on CEUS LI-RADS: preliminary analysis of washout timing & intensity

Within LI-RADS categorization, LR-M nodules are probably or definitely malignant, but not specific for hepatocellular carcinoma (HCC). HCC is variably encountered within the LR-M category, representing 36 to 44% [1, 2]. We analyze CEUS imaging features within LR-M to determine their ability to predict the presence of HCC.

This single-centre preliminary retrospective study reviewed 100 CEUS examinations of LR-M nodules in at-risk livers going backwards from January 2025. CEUS arterial phase enhancement and washout features were documented and classified according to the CEUS LI-RADS v2017 algorithm. Reference standards for HCC diagnosis included histopathology or concordant findings on CT/MR. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each CEUS feature.

Within LR-M, rapid onset of weak washout before 1 min and persisting as weak to 5 min displayed the greatest diagnostic performance for identifying HCC within LR-M. This feature was present in 38/49 (77.6%) of HCCs and achieved a sensitivity of 77.6%, specificity of 64.7%, PPV of 67.9%, and NPV of 75.0%. When combined with non-rim arterial phase hyperenhancement (APHE), rapid onset of weak washout before 1 min increased specificity to 80.4% and reduced sensitivity to 61.2%, with a PPV of 75.0% and NPV of 68.3%. Rim APHE with late weak washout was observed in only 4/49 (8.2%) of HCCs and did not reach statistical significance. Other washout patterns in LR-M nodules proven to be HCC, including rapid marked and late weak washout, were infrequently encountered and demonstrated limited diagnostic value.

Rapid onset of weak washout prior to 1 min and sustained as weak to 5 min, in combination with non-rim APHE, is the most reliable CEUS feature for prediction of HCC within LR-M. Our additional observations for suspicion of HCC within this category facilitate decision-making and patient management. Future investigations should include a prospective, multi-centred effort.