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

Abstract

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. 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. 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. 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. 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.