Imaging description

Nodular regenerative hyperplasia is an increasingly recognized condition characterized by transformation of normal liver parenchyma into hyperplastic regenerative nodules in the absence of fibrosis (the absence of fibrosis distinguishes nodular regenerative hyperplasia from cirrhosis) [1,2]. The condition has been reported in up to 3% of unselected patients at autopsy [3]. From a radiological perspective, there appear to be two forms of the condition: a diffuse form in which the nodules are small and widespread, and a focal form in which the nodules are few in number, scattered throughout the liver, and measure up to a few centimeters in size. In the diffuse form, imaging findings can be subtle across all modalities [2, 4, 5]. At US, multiple masses that are hypo-, iso-, or hyperechoic may be seen (Figure 14.1). AT CT the lesions are usually hypodense with little enhancement. At MRI, nodular regenerative hyperplasia is usually of similar signal intensity to the liver on T1, T2, and post-gadolinium sequences. While the literature on this topic is limited, it seems the nodules may be more obvious on ultrasound than CT or MRI [4], and this has been my experience (Figures 14.1 and 14.2). A periportal distribution has been described [3]. In the focal form of nodular regenerative hyperplasia, multiple hypervascular masses are seen at CT or MRI (Figure 14.3).