Hepatic lymphatics: anatomy and related diseases.

The liver normally produces a large amount of lymph. It is estimated that between 25% and 50% of the lymph received by the thoracic duct comes from the liver. In normal conditions, hepatic lymphatics are not depicted on cross-sectional imaging. They are divided in lymphatics of deep system (lymphatics following the hepatic veins and the portal tract) and those of superficial system (convex surface and inferior surface). A variety of diseases may affect hepatic lymphatics and in general they manifest as lymphedema, lymphatic mass, or cystic lesions. Abnormal distended lymphatics are especially seen in periportal spaces as linear hypoattenuations on CT or strong linear hyperintensities on heavily T2-weighted MR imaging. Lymphatic tumor spread as in lymphoma and lymphangitic carcinomatosis manifests as periportal masses and regional lymph node enlargement. Lymphatic disruption after trauma or surgery is depicted as perihepatic fluid collections of lymph (lymphocele). Lymphatic malformation such as lymphangioma is seen on imaging as cystic spaces of variable size.