Fatty liver
- Focal fatty infiltration tends to have straight, well-defined margins between normal liver
- Fat infiltration is confined to segments and subsegments
- Similarly focal sparing can simulate mass lesions, but again is typically confined to segments and subsegments reflecting vascular flow
NECT
- Normal liver attenuation: 50-65 HU (8-10 HU more than spleen)
- Steatosis: Absolute liver attenuation ≤ 40 HU or at least 10 HU less than that of spleen
- Focal nodular fatty infiltration: Low attenuation
- Common location: Adjacent to falciform ligament
- Due to nutritional ischemia at vascular watershed area
CECT
- Attenuation measurements and comparisons are less reliable than NECT
- Dependent on timing relative to contrast administration
- On venous-phase or delayed CECT, steatotic liver is usually > 35 HU less dense than spleen
- Normal vessels course through fatty infiltration