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Regenerative and Dysplastic Nodules


KEY FACTS

Terminology

  • Localized proliferation of liver parenchyma within cirrhotic liver in response to liver injury

    • May progress to become dysplastic or even malignant [hepatocellular carcinoma (HCC)]

Imaging

  • Multiphasic gadoxetate (Eovist, Primovist)-enhanced MR, plus diffusion-weighted imaging is optimal imaging tool

    • Regenerative: Innumerable nodules in cirrhotic liver with decreased signal intensity on T2WI or GRE

      • –

        Hypovascular without washout or capsule

      • –

        Typically < 2 cm; retain Eovist on delayed phase (brighter than liver)

    • Dysplastic: Fewer, larger, hypovascular, hyperintense (bright) on T1WI and hypointense (dark) on T2WI

      • –

        Usually 2-4 cm in diameter; retain Eovist (bright) on delayed-phase imaging

      • –

        Lesion may have imaging features of both dysplastic and malignant (HCC) nodule; this nodule-in-nodule pattern often suggests malignant degeneration of dysplastic nodule

    • Malignant (HCC): Solitary or several; bright on T2WI and diffusion-weighted imaging

      • –

        Hypervascular with washout on venous and delayed phase; encapsulated

      • –

        Minimal uptake and retention of Eovist (usually)

  • CT: Effective in surveillance; detection and characterization of cirrhosis and HCC

    • Regenerative nodules (RNs): May be seen on NECT as hyperattenuating to surrounding liver

      • –

        CECT: RNs enhance slightly less than liver; disappear

    • Dysplastic nodules: Iso-/hyperattenuating in arterial phase; not hypervascular

    • HCC

      • –

        Hypervascular on arterial phase; washout ± capsule on venous or delayed phase

Top Differential Diagnoses

  • Hepatocellular carcinoma

    • Heterogeneously hypervascular on arterial phase with washout on venous or delayed phase

    • Variably hypointense on T1WI; hyperintense on T2WI (opposite of benign nodules)

  • Nodular regenerative hyperplasia

    • Focal form = " large regenerative nodules "

    • Distinct pathologic entity, associated with Budd-Chiari syndrome

  • Heterogeneously hypervascular on arterial phase with washout on venous or delayed phase is strongly indicative of HCC

  • Other characteristics of HCC: Heterogeneity, multiplicity, encapsulation, venous invasion

Diagnostic Checklist

  • Substantial overlap in imaging appearance of regenerative and dysplastic nodules, and even HCC

  • Imaging allows confident diagnosis of lesions larger than ~ 2 cm

Axial NECT in a 54-year-old woman with primary biliary cirrhosis shows innumerable small, hyperdense, regenerative nodules
surrounded by lace-like fibrosis.

Axial CECT in the same patient demonstrates that the nodules disappear into the background cirrhotic liver, owing to minimal enhancement of the nodules and persistent enhancement of the fibrotic bands. Also noted is prominent porta hepatis lymphadenopathy
, another typical feature of primary biliary cirrhosis.

Axial contrast-enhanced T1WI MR in a 61-year-old woman with cirrhosis shows a nodular liver with widened fissures, typical for cirrhosis. There are innumerable small, hypointense, cirrhotic regenerative nodules
, but these are not very evident.

Axial T2WI MR in the same patient shows the cirrhotic nodules more clearly, as subcentimeter, hypointense ("dark") lesions
, a characteristic appearance of benign regenerative nodules.

TERMINOLOGY

Synonyms

  • Cirrhotic nodules

Definitions

  • Localized proliferation of liver parenchyma within cirrhotic liver in response to liver injury

    • May progress to become dysplastic or even malignant

IMAGING

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