Differentiation of focal nodular hyperplasia from hepatocellular adenomas with low-mechanical-index contrast-enhanced sonography (CEUS): effect of size on diagnostic confidence.

PURPOSE: The purpose of this study was to assess the diagnostic performance of contrast-enhanced sonography (CEUS) for the differentiation of focal nodular hyperplasia (FNH) from hepatocellular adenoma (HCA) according to lesion size.

MATERIALS AND METHODS: Forty patients with a definite diagnosis of FNH or HCA who underwent CEUS were included in this institutional review board (IRB)-approved study. A total of 43 FNHs and 20 HCAs, including 15 inflammatory HCAs and five unclassified HCAs, were analysed. Two radiologists reviewed the diagnostic CEUS parameters separately and in consensus, including the presence or absence of centrifugal filling and central vessels. The sensitivity (Se), specificity (Sp), and inter-observer confidence (Kappa) of CEUS diagnostic parameters were assessed.

RESULTS: Inter-observer agreement of CEUS for FNH diagnosis was high (kappa = 0.81) with an overall Se of 67.4% [29/43 (CI 95%: 51.4-80.1 %)] and an Sp of 100% [20/20 (CI 95%: 81-100%)]. Significantly higher Se figures were found for lesions ≤ 35 mm than for lesions > 35 mm [respectively, 93 % (28/30) (CI 95%: 77.6-99.2) vs. 7.7% (1/13) (CI 95%: 0.2-36%), p = 0.002] with unchanged specificity.

CONCLUSION: CEUS is highly specific for the diagnosis of FNH, with very good inter-observer agreement, whatever the size, but its sensitivity is significantly reduced in diagnosing lesions larger than 35 mm.

KEY POINTS: • CEUS is highly specific for the diagnosis of FNH, regardless of lesion size • CEUS shows reduced sensitivity in diagnosing FNH lesions larger than 35 mm • The filling patterns of hepatocellular adenomas are not affected by lesion size.