Frequency and implication of focal fatty sparing in segmental homogeneous fatty liver at ultrasound

The purpose of this study was to investigate whether focal fatty sparing arises from preexisting segmental homogeneous nonalcoholic fatty liver (NAFL).

Patients with various patterns of fatty liver were recruited from among 16,127 people, and 132 participants with segmental homogeneous NAFL were followed during the second year. All participants underwent ultrasonography. The sonographic findings in segmental homogeneous NAFL were analyzed.

Of the 16,127 participants, 1,619 had fatty liver (10.0 %), and of these 1,568 had NAFL (9.72 %) and 51 had alcoholic fatty liver (0.31 %). Of the 1,568 patients with NAFL, 176 had homogeneous fatty liver with focal fatty sparing (11.2 %), 132 had segmental homogeneous fatty liver (8.42 %), and the rest had other patterns. At follow-up, of the 132 patients with segmental homogeneous fatty liver, 3 (2.3 %) were found to have a normal liver and 26 (19.7 %) diffuse homogeneous and heterogeneous fatty liver, and no focal fatty sparing was found (P < 0.001).

Focal fatty sparing usually does not arise in preexisting segmental homogeneous NAFL. This implies that newly appearing nodular hypoechogenicity in segmental homogeneous fatty liver is more likely to be a true lesion rather than focal fatty sparing.