An enlarged spleen (splenomegaly) is not a disease in itself but the result of an underlying disorder. Many disorders can make the spleen enlarge. To pinpoint the cause, doctors must consider disorders ranging from chronic infections to blood cancers.
An enlarged spleen may outgrow its own blood supply. When parts of the spleen do not get enough blood, they may become damaged, causing them to bleed or die.
The spleen normally removes old and/or damaged red blood cells from the bloodstream. However, when the spleen enlarges, it traps and stores an excessive number of red blood cells, causing anemia. Sometimes, the spleen also destroys white blood cells and/or platelets. This process creates a vicious circle: the more cells the spleen traps, the larger it grows, and the larger it grows, the more blood cells it traps and destroys.
An enlarged spleen does not cause many symptoms, and the symptoms that it does cause may be mistaken for many other medical conditions. Because the enlarged spleen lies next to the stomach and sometimes presses against it, people may feel full after eating a small snack or even without eating. People may also have abdominal or back pain in the area of the spleen in the upper left part of the abdomen or the left side of the back. The pain may spread to the left shoulder, especially if parts of the spleen do not get enough blood and start to die.
If hypersplenism causes severe anemia, people may be tired and short of breath. People may also have frequent infections as a result of too few white blood cells, and the tendency to bleed as a result of too few platelets.
Doctors may suspect that the spleen is enlarged when people complain of fullness or pain in the upper left portion of the abdomen or back. Usually, doctors can feel an enlarged spleen during a physical examination. An x-ray of the abdomen may also show that the spleen is enlarged. In some cases, ultrasonography or computed tomography (CT) is needed to determine how large the spleen is and whether it is pressing on other organs. Magnetic resonance imaging (MRI) provides similar information and also traces blood flow through the spleen. Other specialized scanning techniques use mildly radioactive particles to assess the spleen's size and function and to determine whether it is accumulating or destroying large numbers of blood cells.
Blood tests show decreased numbers of red blood cells, white blood cells, and platelets. When blood cells are examined under a microscope, their shape and size may provide clues to the cause of the spleen enlargement. An examination of bone marrow (see Symptoms and Diagnosis of Blood Disorders: Bone Marrow Examination) may show cancer of the blood cells (such as leukemia or lymphoma) or an accumulation of unwanted substances (such as occurs in storage diseases). Blood protein measurement can determine whether other conditions are present that can cause the spleen to enlarge, such as amyloidosis, sarcoidosis, malaria, kala-azar, brucellosis, and tuberculosis. Liver function tests help determine whether the liver is also diseased.
Doctors cannot easily remove a sample of the spleen for examination because inserting a needle or cutting spleen tissue may cause uncontrollable bleeding. If an enlarged spleen is removed during surgery to diagnose or treat certain diseases, the spleen is sent to a laboratory, where the cause of enlargement can usually be determined.
When possible, doctors treat the underlying disorder that caused the enlarged spleen. People with an enlarged spleen should avoid contact sports because an enlarged spleen is more likely to tear, causing uncontrollable bleeding.
Surgical removal of the spleen (splenectomy) should be avoided whenever possible because it can cause problems, including an increased susceptibility to infections by certain bacteria. However, the risks are worth taking in certain critical situations:
As an alternative to surgery, radiation therapy can sometimes be used to shrink the spleen. People who have had their spleen removed need to be vaccinated against infections caused by Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. They should also make sure they receive the influenza vaccine every year, as is now recommended for all people.
Last full review/revision August 2012 by Harry S. Jacob, MD