Regenerative nodules in liver
Regenerative hepatic nodules (RNs) are a form of non neoplastic nodules that arise in a cirrhotic liver. This may be slightly different from the term nodular regenerative hyperplasia which are described histopathologically as regenerative nodules with little or no hepatic fibrosis and largely healthy hepatic architecture 1.
They can be of two types:
- micronodules <3mm
- macronodules >3mm
There may be accumulation of iron in the nodules when they are termed siderotic nodules.
Regenerative nodules are rarely visible on non-contrast CT unless they are siderotic. Siderotic regenerative nodules (containing iron) are hyperdense to liver on precontrast imaging and become isodense to liver on post contrast phases.
They enhance similar to the normal liver parenchyma and thus may not be distinguishable in cirrhotic liver. There is no arterial phase enhancement.
CT arterial portography (CTAP)
RNs are generally visualized as enhancing nodules surrounded by lower attenuation thin septa.
CT hepatic arteriography (CTHA)
RNs are generally visualized as non-enhancing nodules surrounded by enhancing fibrous septa.
CTHA is considered more sensitive than the former in depicting regenerative nodules 4.
About 25% of regenerative liver nodules have increased iron deposition (siderotic nodules) in comparison to normal hepatocytes, which is why they may be hypointense on T2 and T2*.
They usually do not enhance or enhance less than the liver parenchyma.
Imaging cannot reliably differentiate nondysplastic from dysplastic siderotic nodules. Depending on a nodule's overall imaging characteristics, it may be classified with LI-RADS as less likely or more likely to represent early hepatocellular carcinoma. A regenerative nodule that is probably benign meets LR2 cirrhosis-associated nodule criteria.
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