Splenomegaly

Splenomegaly is defined as the enlargement of the spleen measured by weight or size. The spleen plays a significant role in hematopoiesis and immunosurveillance. The major functions of the spleen include clearance of senescent and abnormal erythrocytes and their remnants, opsonized platelets and white blood cells, and removal of microorganisms and antigens. The spleen also serves as a secondary lymphoid organ and is the site for the maturation and storage of T and B lymphocytes, playing an important role in the synthesis of immunoglobulin G (IgG) by mature B-lymphocytes upon interaction with the T-lymphocytes.  The spleen also synthesizes the immune system peptides properdin and tuftsin. Approximately one-third of circulating platelets are stored in the spleen. The normal position of the spleen is within the peritoneal cavity in the left upper quadrant adjacent to ribs 9 through 12. The normal-sized spleen abuts the stomach, colon, and left kidney. The size and weight of the spleen may vary and correlate with the weight, height, and sex of an individual, with larger spleen size seen in men compared to women and in heavier or taller individuals. A normally sized spleen measures up to 12 cm in craniocaudal length.  A length of 12 cm to 20 cm indicates splenomegaly and a length greater than 20 cm is definitive of massive splenomegaly. The normal weight of the adult spleen is 70 g to 200 g; a spleen weight of 400 g to 500 g indicates splenomegaly and a spleen weight greater than 1000 g is definitive of massive splenomegaly. The normal-sized spleen is usually not palpable in adults. However, it may be palpable due to variations in body habitus and chest wall anatomy. Splenomegaly may be diagnosed clinically or radiographically using ultrasound, CT imaging, or MRI.  Splenomegaly may be a transient condition due to acute illness or may be due to serious underlying acute or chronic pathology.