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Enlarged Spleen: Causes, Symptoms, and Treatments

What is the spleen and what causes an enlarged spleen (splenomegaly)?

The spleen sits under your rib cage in the upper left part of your abdomen toward your back. It is an organ that is part of the lymph system and works as a drainage network that defends your body against infection.

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White blood cells produced in the spleen engulf bacteria, dead tissue, and foreign matter, removing them from the blood as blood passes through it. The spleen also maintains healthy red and white blood cells and platelets; platelets help your blood clot. The spleen filters blood, removing abnormal blood cells from the bloodstream.

A spleen is normally about the size of your fist. A doctor usually can't feel it during an exam. But diseases can cause it to swell and become many times its normal size. Because the spleen is involved in many functions, many conditions may affect it.

An enlarged spleen is not always a sign of a problem. When a spleen becomes enlarged, though, it often means it has been doing its job but has become overactive. For example, sometimes the spleen is overactive in removing and destroying blood cells. This is called hypersplenism. It can happen for many reasons, including problems with too many platelets and other disorders of the blood.

Causes of an Enlarged Spleen

An enlarged spleen can be caused by infections, cirrhosis and other liver diseases, blood diseases characterized by abnormal blood cells, problems with the lymph system, or other conditions.

Here are some common causes of an enlarged spleen:


  • Viral infections, such as mononucleosis
  • Parasitic infections, such as toxoplasmosis
  • Bacterial infections, such as endocarditis (an infection of your heart's valves)


Other causes of an enlarged spleen include:

  • Inflammatory diseases such as sarcoidosis and rheumatoid arthritis
  • Trauma, such as an injury during contact sports
  • Cancer that has spread (metastasized) to the spleen
  • A cyst, a noncancerous fluid-filled sac
  • A large abscess, a pus-filled cavity usually caused by a bacterial infection
  • Infiltrative diseases such as Gaucher's disease, amyloidosis, or glycogen storage diseases

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