Diagnostic performance of contrast-enhanced US in small liver nodules not conclusively characterized after MRI in cirrhotic patients.

Objective: In patients at risk of hepatocellular carcinoma (HCC), new focal liver lesions identified at ultrasound screening require further characterization by CT or MRI. If these techniques cannot conclusively characterize a lesion, a biopsy or an alternative imaging modality such as contrast-enhanced ultrasound (CEUS) is considered. We aimed to determine the diagnostic yield of CEUS in a sequential noninvasive diagnostic strategy for solitary nodules ≤ 20 mm detected in cirrhotic patients during US surveillance characterized as inconclusive on MRI.

Methods: Post hoc analysis of a single-center prospective cohort of high-risk patients (Child A or B) with no prior history of HCC and new liver nodules (≤ 20 mm) detected on screening US who underwent CEUS after inconclusive MRI (LI-RADS-2, LI-RADS-3, LI-RADS-4, or LI-RADS-M) between January 2006 and February 2017. We compared the characterization of nodules by LI-RADS v.2018 alone vs characterization after considering subsequent CEUS-LR v.2017 against the final diagnosis by biopsy or follow-up.

Results: Of the 75 nodules included, CEUS upgraded 45 (63.4%); of these, 13 nodules classified as LR3 or LR4 at MRI were classified as CEUS-LR5. Altogether, 15 (21.1%) nodules inconclusive on MRI were classified as CEUS-LR5. CEUS yielded 37.5% (95% CI: 22.73‒54.20%) sensitivity and 100% specificity (95% CI: 88.78-100%) for HCC.

Conclusion: Adding CEUS to the workup of liver nodules with inconclusive MRI findings demonstrated high specificity for HCC, particularly benefiting nodules categorized as LR3 at MRI.

Key Points: Question MRI's limited sensitivity in diagnosing small HCCs in cirrhotic patients results in inconclusive classification of a high proportion of screening-detected lesions. Findings Adding CEUS to the work-up for inconclusive liver nodules at MRI yielded 100% specificity (95% CI: 88.78-100%) and 37.5% (95% CI: 22.73-54.20%) sensitivity for the HCC diagnosis. Clinical relevance CEUS is a valuable problem-solving tool in the work-up of small liver nodules with inconclusive MRI findings in cirrhotic patients.