Regenerative liver nodule
Regenerative liver 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. When there is accumulation of iron in the nodules, they are called siderotic nodules.
RNs form in the setting of necrosis or RNs can be of three types 5:
- micronodules <3 mm
- macronodules >3 mm
- giant RNs > 5 cm (rare)
RNs appear as round, well-defined nodules (usually in the thousands) present throughout the liver with surrounding fibrosis 5.
On post-contrast CT and MRI RNs enhance similar to the normal liver parenchyma in both portal venous and hepatocellular/delayed phases, and thus may not be distinguishable in a cirrhotic liver. There is no arterial phase enhancement.
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.
CT arterial portography (CTAP)
Contrast injection into the superior mesenteric artery (after arterial vascular access). RNs are generally visualized as enhancing nodules surrounded by lower attenuation thin septa.
CT hepatic arteriography (CTHA)
Contrast injection into the common hepatic artery (after arterial vascular access). RNs are generally visualized as nonenhancing nodules surrounded by enhancing fibrous septa.
CTHA is considered more sensitive than the former in depicting regenerative nodules 4.
RNs are common in a cirrhotic liver:
- T1: variable
- T2: hypointense
- T2*: hypointense
They usually do not enhance, or enhance less than the liver parenchyma.