Hyperintense liver lesions on hepatobiliary phase of gadoxetic acid-enhanced magnetic resonance imaging: clinical insights and significance.

Hepatobiliary (HB)-specific magnetic resonance imaging (MRI) contrast agents, particularly gadoxetic acid, are being increasingly utilized for liver imaging, with well-established clinical utility. The most distinctive feature of gadoxetic acid is HB phase imaging performed 20 min after administration. In clinical practice, most focal liver lesions lack gadoxetic acid uptake and appear hypointense against the background of normally enhancing liver parenchyma owing to the absence of hepatocyte function within the tumor tissue. Less commonly, various liver lesions show hyperintensity on HB phase imaging, which is a characteristic diagnostic feature. Hyperintense lesions in the HB phase are crucial diagnostic elements and imaging biomarkers. Hyperintense hepatocellular carcinoma (HCC) demonstrates lower malignancy and a generally good prognosis, but exhibits poorer response to immunotherapies, including anti-programmed cell death inhibitors. Heterogeneously hyperintense HCCs show poor treatment outcomes. Hepatocellular adenomas with β-catenin mutation exhibit HB phase hyperintensity with signal-intensity patterns capable of discriminating malignant transformation potentials based on exon 3 mutation. Focal nodular hyperplasia (FNH) and FNH-like lesions show HB phase hyperintensities with various signal-intensity patterns, significantly reducing unnecessary biopsies for diagnosis. Nodular regenerative hyperplasia and regenerative and multiacinar regenerative nodules also present hyperintensity or ring-like hyperintensity in the HB phase but no enhancement in the arterial phase. Cloud enhancement in intrahepatic cholangiocarcinoma serves as both a key differential diagnostic feature and a poor prognostic indicator. Liver metastases from colorectal, breast, and pancreatic adenocarcinomas occasionally contain mildly hyperintense areas that may correlate with a poor prognosis or lower chemotherapy response. Peritumoral hyperintensity can be identified in hypervascular lesions and relatively large tumors; however, its clinical significance has not yet been established. Understanding hyperintensity patterns in the HB phase aids in accurate imaging diagnosis and offers valuable prognostic and therapeutic biomarker information. This review explores the clinical significance, diagnostic implications, and prognostic value of hyperintense lesions on gadoxetic acid-enhanced MRI.