Inflammation, things like hepatitis, I copied the following from webmd
Causes of an Enlarged Liver
An enlarged liver may occur as a result of one or more of these causes.
Inflammation or fatty liver may cause an enlarged liver and may result from:
An infection such as a from a virus or abscess
Certain medications
Toxins
Certain types of hepatitis, including alcoholic hepatitis
Autoimmune disease
Metabolic syndrome
Genetic disorders that cause fat, protein, or other substances to build up
Abnormal growths may cause an enlarged liver. This may result from:
Cysts
Tumors that start or spread to the liver
A problem with blood flow can cause the liver to enlarge. This may be due to a variety of conditions such as:
Congestive heart failure, a condition where the heart fails to pump blood well
Hepatic vein thrombosis, a blockage of veins in the liver
Veno-occlusive disease, a blockage of small veins in the liver
As you know your own medical history something may leap out as more likely.