Pseudotumor of the quadrate lobe in hepatic sonography: a sign of generalized fatty infiltration.

Sonograms of 43 patients demonstrated a focal area of decreased echogenicity in the medial segment of the left hepatic lobe (quadrate lobe). The shape ranged from ovoid to sheetlike, and the diameter ranged from 0.7 to 8.6 cm. The echogenicity of the right hepatic lobe was abnormally increased in 34 of 37 scans graded. In 20 patients with follow-up sonograms, 11 showed no change, six disappeared and three decreased in size. In 12 patients with unenhanced CT scans, 10 had decreased attenuation of the hepatic parenchyma and normal attenuation in the observed quadrate lobe focus. The hypoechoic focus in the quadrate lobe represents focal sparing in generalized fatty infiltration of the liver. When present, this focus represents a useful qualitative sign of generalized fatty infiltration in the rest of the liver.