An organ that removes worn-out and defective red blood cells from the circulation and helps to fight infection by producing some of the antibodies, lymphocytes, and phagocytes that destroy invading microorganisms. The spleen is a fist-sized, spongy organ in the upper left abdomen behind the lower ribs. The spleen enlarges in many diseases. These include infections such as malaria and infectious mononucleosis; blood disorders such as leukaemia, thalassaemia, and sickle cell anaemia; and tumours such as lymphomas. Enlargement of the spleen may be accompanied by hypersplenism. The spleen may be ruptured by a severe blow to the abdomen. This can cause potentially fatal haemorrhage, and an emergency splenectomy is needed.


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