Splenomegaly is an enlarged spleen The spleen is located on the left side of the abdomen just beneath the diaphragm If you place your left palm flat on your abdomen with the middle finger touching the umbilicus and pointing to your right hip, the heel of your palm is approximately in the spot where your spleen is Splenomegaly occurs when the spleen has a disease, or when portal hypertension develops due to liver disease Splenomegaly often occurs during the disease mononucleosis (called the "kissing disease")