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.
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)
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
Symptoms of an Enlarged Spleen
Most people don't know they have an enlarged spleen because symptoms are rare. People usually find out about it during a physical exam. These are the most common symptoms of an enlarged spleen:
Being unable to eat a large meal.
Feeling discomfort, fullness, or pain on the upper left side of the abdomen; this pain may spread to your left shoulder.
If you have pain that is severe or gets worse when taking a deep breath, see your doctor right away.
If you have an enlarged spleen, you may develop other signs or symptoms, too. These are related to the underlying disease. They may include signs and symptoms such as:
Your doctor will ask you questions and do a physical exam to diagnose an enlarged, painful spleen. This involves palpating (examining by touch) your spleen. You will also likely need diagnostic tests to confirm the cause of the swollen spleen. These may include blood tests, an ultrasound, or computerized tomography (CT) scan. In some cases, other tests may be needed.