Liver

The normal liver demonstrates diffuse FDG uptake (typically greater than or equal to the spleen).

Many readers consider the uptake in the liver to represent the “background metabolic activity” for an exam. 

For assessment of many lesions found in the body, the metabolic activity of the liver serves as the reference threshold by which to decide what is benign (uptake < liver) and what is malignant (uptake > liver). 

Focal increased FDG uptake in the liver is always highly suspicious for malignancy. Very commonly, these malignant lesions may be poorly delineated on the co-registered CT images due to the lack of intravenous contrast administration. 

Non-avid, low attenuation liver lesions are almost always benign (usually representing cysts, hemangiomas or fully treated malignant lesions), although some hepatocellular carcinomas can demonstrate only very mild metabolic activity.

The following liver topics are covered separately: 

• The Heterogeneous Liver  (here)
• Liver Ablation  (here)
• Primary Liver Malignancies  (here)
• Hypermetabolic Geographic Focal Fatty Infiltration  (here)
• Hepatic Adenoma  (here)