Hepatic attenuation on CT (reflected by Hounsfield values) depends on a combination of factors including the presence or absence (as well as phase) of IV contrast administration.
Several intrinsic liver pathologies can be attributed a diffuse change in liver attenuation with a amount of hepatic fat being the most prevalent.
http://radiopaedia.org/articles/hepatic-attenuation-on-ct

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Causes of diffusely decreased attenuation. diffuse fatty infiltration (diffuse hepatic steatosis); diffuse malignant infiltration; diffuse non malignant infiltrative ...


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A parallel phenomenon is the low hepatic attenuation seen in patients with liver steatosis. In the pre-contrast (native) CT, the attenuation of the incidentaloma is ...
https://books.google.com/books?id=3oW8BAAAQBAJ&pg=PA146&lpg=...
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Obese patient with low hepatic attenuation consistent with diffuse steatosis.

https://books.google.com/books?id=tE1QaGm9swUC&pg=PA160&lpg=...

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Contrast-enhanced CT scan shows low hepatic attenuation at portal venous phase suggestive of hepatic steatosis.
http://journals.lww.com/ultrasound-quarterly/_layouts/oaks.j...
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Obese patient with low hepatic attenuation consistent with diffuse steatosis. Areas of focal fatty sparing displaying normal attenuation values are recognized at ...
http://famona.sezampro.rs/medifiles/radiology/focal liver le...