Focal fatty sparing usually does not arise in preexisting nonalcoholic diffuse homogeneous fatty liver

The purpose of this study was to investigate whether focal fatty sparing can arise in preexisting nonalcoholic diffuse homogeneous fatty liver and its clinical implications.

This prospective study consisted of 2 parts. In the first part, 8598 people (5202 men and 3396 women; mean age ± SD, 43.4 ± 28.3 years; range, 18-82 years) were consecutively evaluated with sonography for abnormal liver findings; in the second part, participants with diffuse homogeneous fatty liver were followed over approximately 3 years. Sonographic findings of the participants in the first year and findings of the participants with diffuse homogeneous fatty liver in the first and third years were analyzed.

In the first part, 778 of 8598 participants (9.05%) were found to have fatty liver, including 752 cases of nonalcoholic diffuse fatty liver (8.75%) and 26 cases of alcoholic fatty liver (0.30%). Of the 752 cases of nonalcoholic diffuse fatty liver, 301 participants had nonalcoholic diffuse homogeneous fatty liver, and 68 (9.04%) had focal fatty sparing. In the second part, the 301 participants with nonalcoholic diffuse homogeneous fatty liver (205 men and 96 women; mean age, 39.6 ± 10.4 years; range, 18-60 years) were followed. In the third year, 2 cases of fatty liver (0.67%) had resolved, 2 cases (0.67%) had inflammatory pseudotumors, and no focal fatty sparing was found (P < .001).

The findings of this study suggest that focal fatty sparing usually does not arise in preexisting nonalcoholic diffuse homogeneous fatty liver, and a newly emerging abnormality is more likely a true lesion.