Liver stiffness measurement in patients with nodular regenerative hyperplasia undergoing magnetic resonance elastography

Purpose Nodular regenerative hyperplasia (NRH) may mimic cirrhosis at imaging. We aim to investigate the effect of NRH on liver stiffness measurement (LSM) obtained with magnetic resonance elastography (MRE).Methods This retrospective, Institutional Review Board-approved study included 37 subjects with NRH (Group 1) and no or minimal fibrosis (F0-F1), a control group (Group 2) made of 30 subjects with non-advanced fibrosis (F0-F2), and a control group (Group 3) made of 30 subjects with advanced fibrosis (F3-F4), all with available MRE. LSM was measured in each subject along with assessment of hepatic morphological features of cirrhosis and signs of portal hypertension. The significance of the difference in mean LSM between Group 1 and 2 and between Group 1 and 3 was evaluated using the Mann-Whitney U test. The difference in distribution of imaging features among groups was assessed using the Pearson chi(2) or Fisher exact test.Results The mean +/- SD LSM in Group 1 (3.56 +/- 1.10 kPa) was significantly higher compared to Group 2 (2.91 +/- 0.52 kPa, P = 0.019) and significantly lower compared to Group 3 (7.18 +/- 2.08 kPa, P < 0.001). Twelve (32%) patients with NRH had LSM >= 4.11 kPa, and 6 (16%) patients had LSM >= 4.71 kPa. Surface nodularity (P = 0.032) and caudate lobe hypertrophy (P = 0.004) were more commonly visualized in Group 1 than in Group 2. At least one feature of portal hypertension was observed in 16 (43%) NRH subjects.Conclusion NRH may increase the LSM obtained with MRE and may represent a confounding factor when using liver stiffness for the non-invasive diagnosis of fibrosis.