Causes of splenomegaly
The etiology of splenomegaly includes a wide variety of diseases. Almost all causes of the enlarged spleen are due to systemic disorders that affect organs of multiple systems. We will summarize the most common causes of splenomegaly into:
1- Infection is the most common cause of enlarged spleen. Spleen, as mentioned, is a lymphoid organ that plays an immunological role therefore infections may result in splenomegaly. Splenomegaly is caused by infection with different microorganisms. Viral infection such as mononucleosis which is caused by the Epstein bar virus is believed to cause splenomegaly.
Parasitic infections with toxoplasma and malaria are found to cause splenomegaly, particularly in developing countries. Kala-azar which is a type of tropical leishmaniasis is believed to be one of the most common causes of severe splenomegaly.
Acute typhoid infection is considered the most common bacterial infection causing splenomegaly. Syphilis and TB (tuberculosis) are also examples of bacterial infections that may cause spleen enlargement. Spleen abscess is one of the most serious causes of enlarged spleen, yet patients with spleen abscess usually complain first from splenic throbbing pain and fever.
2- Liver diseases are a well-known cause of splenomegaly. Spleen is connected with the liver by a splenic vein which takes part in forming a portal vein that pours in the liver. Diseases affecting the function of the liver such as liver cirrhosis or liver cell failure will subsequently affect the spleen drainage system leading to spleen congestion and enlargement.
3- Heart failure whether RSHF (right-sided heart failure) or congested heart failure will mostly cause splenomegaly as a part of systemic venous congestion.
4- Hemolytic anemia is a type of anemia characterized by an increased rate of RBCs destruction (hemolysis). Over loading, the spleen with many destroyed red blood cells forces it to be more functioning consequently larger in size. Other hematological disorders such as polycythemia, thalassemia, and spherocytosis could be presented with splenomegaly.
5- Malignancy is less common to primary develop in the spleen but it is often metastasis from a tumor of another organ that circulates in the blood to settle in the spleen to be called a secondary tumor. Spleen secondary tumor grows and proliferates into spleen tissue causing splenomegaly. Leukemia, malignancy of the blood-forming tissue in the bone marrow is documented to cause splenomegaly due to disturbance in the differentiation, maturity, and morphology of the blood cells.
6- Decreased flow (stasis) of the spleen venous drainage, as well as lymphatic drainage, could cause splenomegaly. Splenic venous stasis may be caused by portal hypertension, hepatic vein obstruction, and splenic vein obstruction.
7- Other causes of splenomegaly include sarcoidosis, rheumatic arthritis (felty syndrome), systemic lupus, amyloidosis, and collagen vascular diseases.
8- Idiopathic splenomegaly is defined as splenomegaly of unknown cause which is usually diagnosed by exclusion of the previously mentioned causes.
