Hepatic steatosis can be quantified using the absolute unenhanced CT
attenuation measured in Hounsfield units. Relative liver-spleen
Hounsfield unit difference can be used when iodinated contrast material
has been administered. An important pitfall to avoid is use of arterial
phases where the spleen enhances earlier than the liver, which could be
mistaken for hepatic steatosis using the spleen as the reference. CT
scans obtained in a patient (A) before and
(B–D) after contrast material administration in
the arterial (B), late arterial (C), and
portal venous (D) phases. No steatosis is seen on
unenhanced CT scan (65 HU) (A). CT scans obtained in early
(B) and late (C) arterial phase show liver
Hounsfield unit is 40 HU and 220 HU less, respectively, than that in the
spleen, mimicking steatosis. In portal venous phase (D),
attenuation of liver and spleen is essentially equal.