Multifocal nodular fatty infiltration of the liver mimicking metastatic disease on CT: imaging findings and diagnosis using MR imaging

The aim of this study was to describe the LR appearance of multifocal nodul ar fatty infiltration of the liver (MNFIL) using T1-weighted in-phase (IP) and opposed-phase (OP) gradient-echo as well as T2-weighted turbo-spin-echo sequences with fat suppression (FSTSE) and without (HASTE). Magnetic reson ance imaging examinations at 1.5 T using T1-weighted IP and OP-GRE with fas t low angle shot (FLASH) technique, and T2-weighted FSTSE, T2-weighted HAST E of 137 patients undergoing evaluation for focal liver lesions were review ed. Five were identified in whom CT indicated metastatic disease; however, no liver malignancy was finally proven. Diagnosis was confirmed by biopsy ( n = 3), additional wedge resection (n = 1) or follow-up MRI 6-12 months lat er (n = 5). Regarding the identified five patients, the number of focal liv er lesions was 2 (n = 2) and more than 20 (n = 3). The MR imaging character istics were as follows: OF-image: markedly hypointense (n = 5); IP image: i sointense (n = 2) or slightly hyperintense (n = 3); T2-weighted FSTSE-image : isointense (n = 5); T2-weighted HASTE image isointense (n = 1); slightly hyperintense (n = 4). OP images all lesions were sharply demarcated of almo st spherical configuration (n = 5). Further evaluation by histology or foll ow-up MR imaging did not give evidence of malignancy in any case. Histology revealed fatty infiltration of the liver parenchyma in three patients. Mag netic resonance follow-up showed complete resolution in two patients and no change in three patients. Multifocal nodular fatty infiltration can simula te metastatic disease on both CT and MR imaging. The combination of in-phas e (IP) and opposed-phase (OP) gradient-echo imaging can reliably differenti ate MNFIL from metastatic disease.