* When the craniocaudal length of the spleen is more than 12 or 13cm (varies depending on the race, gender etc) we call it a case of splenomegaly. Though the size of the spleen can be measured in both sagittal as well as coronal planes, i prefer taking the largest value in whichever plane it is.
* There are numerous causes of splenomegaly based on age and previous clinical history.
* The spleen could enlarge in size because its work (Spleen destroys and removes the defective RBCs from circulation) need has increased in view of more and more RBCs being defective like in diseases where the RBCs are spherical rather than biconcave (Hereditary Spherocytosis), or the RBCs are defective because of abnormal hemoglobin in them (Thalassemia) or other hemoglobinopathies.
* The spleen's work load could also increase as a reaction to infections like Infectious mononucleosis, AIDS, viral hepatitis, typhoid, malaria and many more diseases.
* Causes of disordered immunoregulation like Rheumatoid arthritis and SLE also can cause splenomegaly due to increased function of the spleen.
* Abnormal blood flow related to obstruction of the hepatic or portal or splenic vein obstruction can also cause splenomegaly.
* Sometimes the spleen is infiltrated with different kinds of substances causing it to increase in size like Gaucher disease and other glycogen storage diseases and also leukemias.
* Though the causes of splenomegaly are manifold, the causes of massive splenomegaly (that is the weight of the spleen measures more than a kilogram - A craniocaudal length criteria would be preferable i suppose) are only few :
1.Visceral Leishmaniasis.
2.Splenic marginal zone lymphoma.
3.CML
4.Myelofibrosis.
5.Malaria.
