Objectives: The purpose of this study was to investigate the stability of focal fatty sparing of the liver and its clinical implications.
Methods: This prospective study consisted of 2 parts. In the first part, patients who underwent sonography and computed tomography (CT) or magnetic resonance imaging (MRI) were selected, and abnormal findings including focal and diffuse liver abnormalities were documented. In the second part, patients with nonalcoholic hepatic steatosis and focal fatty sparing were included and underwent follow-up with sonography in the second and third years (study interval, 34-37 months; mean ± SD, 35.9 ± 1.14 months). Some cases of focal fatty sparing that were not appreciable on sonography in the third year were reevaluated with CT.
Results: A total of 6781 patients with nonalcoholic hepatic steatosis and focal abnormalities were found among 35,337 people undergoing liver sonography; 2133 underwent CT, MRI, biopsy, or a combination thereof. Eighty-nine of those patients (63 male and 26 female; mean age, 37.6 ± 17.5 years; range, 18-72 years) with hepatic steatosis and focal fatty sparing were finally included. In the second part of the study, focal fatty sparing was appreciable on follow-up sonography in 78 cases (87.6%) and 61 cases (68.5%) in the second and third years, respectively. The hepatic steatosis resolved in the third year in 4 patients, and 26 of 28 cases (92.8%) of focal fatty sparing that were not appreciable on follow-up sonography were found on CT in the third year.
Conclusions: Focal fatty sparing may change with fatty liver changes over time, and it is sometimes not appreciable on sonography, although it is often evident on CT. These findings imply that if differentiation between focal fatty sparing and a tumor is undetermined and follow-up is performed, should any change occur, then an abnormality that is no longer appreciable at follow-up is probably focal fatty sparing rather than a true tumor.
Keywords: computed tomography; focal fatty sparing; hepatic steatosis; magnetic resonance imaging; sonography.