What does hepatic iron deposition look like on CT and MRI, and what are its major causes?
Iron deposition leads to diffusely increased hepatic attenuation >75 HU on CT and decreased T1-weighted and T2-weighted signal intensity of the liver on MRI, which is particularly accentuated on in-phase T1-weighted MR images.
In primary (genetic) hemochromatosis, an autosomal recessive condition, there is increased iron overload related to abnormally increased iron absorption through the duodenum and jejunum. As a result, iron is primarily deposited in the liver parenchyma, and to a lesser extent in the pancreas, myocardium, joints, endocrine glands, and skin, leading to organ damage. Iron deposition in the spleen and bone marrow is not seen. Cirrhosis occurs in one third of patients, and patients have an approximately 200-fold increased risk of HCC.
In secondary hemosiderosis, there is iron accumulation in the reticuloendothelial system, namely the liver, spleen, and bone marrow, secondary to either high dietary iron intake or chronic anemia with repeated blood transfusions. However, organ function is usually preserved.