Causes and PathogenesisTop
Splenomegaly is the term describing an enlarged spleen. In adults the spleen should not be palpable on physical examination; a palpable spleen is enlarged ≥1.5 times. The severity of splenomegaly is determined by the distance from its palpable border to the left costal margin.
1) Infections: Bacterial (tuberculosis, salmonella, brucella, infective endocarditis), viral (cytomegalovirus, viral hepatitis, infectious mononucleosis, herpesvirus type 6, HIV), protozoal (malaria, toxoplasmosis, leishmaniasis, schistosomiasis), abscess.
2) Malignancy: Myeloproliferative neoplasms (primary myelofibrosis, chronic myeloid leukemia, polycythemia vera, essential thrombocythemia), lymphoma, leukemia (acute or chronic), solid tumors (primary splenic or metastatic), multiple myeloma.
3) Autoimmune and systemic diseases: Rheumatoid arthritis (Felty syndrome), systemic lupus erythematosus (SLE), adult-onset Still disease, autoimmune thrombocytopenia, drug-induced reactions, sarcoidosis, primary or secondary amyloidosis.
4) Portal hypertension: Cirrhosis, Budd-Chiari syndrome, portal vein obstruction (thrombus, stenosis, congenital cavernous transformation, compression by lymph nodes and tumors), splenic vein obstruction (thrombus, stenosis, aneurysm, compression by pancreatic or other tumors).
5) Hemolytic anemia: Congenital or acquired (including autoimmune), sickle cell disease (in children).
6) Storage diseases: Gaucher disease, Niemann-Pick disease, mucopolysaccharidosis.
7) Other conditions (rare): Cysts (congenital, posttraumatic, postinfarction, hydatid), nonmalignant tumors of the spleen, hemophagocytic lymphohistiocytosis (HLH), use of granulocyte colony-stimulating factor (G-CSF).
Splenomegaly may lead to hypersplenism (sequestration and excessive destruction of blood cells by macrophages in the spleen). This usually affects all lineages but may be limited to 1 or 2. Features of hypersplenism are independent of the degree of spleen enlargement. If the enlargement is caused, for example, by amyloidosis or metastasis, hypersplenism does not occur. In the case of splenic enlargement in the course of lymphoproliferative neoplasms, the features of hypersplenism are not as pronounced as in the case of portal hypertension or Gaucher disease, even in patients with a large spleen.
A negative palpation result does not exclude splenomegaly and hypersplenism. However, splenomegaly is usually an incidental finding on ultrasonography or computed tomography (CT) imagining done for another reason; if marked, it could be detected during clinical examination.
Diagnostic studies depend on the suspected underlying condition. Ultrasonography and CT are used to assess spleen size, presence of focal lesions, and accessory spleens. Note that if the distance from the palpable border of the spleen to the left costal margin is >10 cm (this is usually equivalent to crossing the midline), it is most frequently a result of a hematologic disease.
Hypersplenism is confirmed by complete blood count (CBC) (cytopenia) and bone marrow aspiration (increased hematopoiesis). The most reliable study is radionuclide imaging using a technetium isotope, which shows increased activity of splenic macrophages.
Specific elements of history and physical examination may be helpful in the diagnostic process. For example, symptoms such as fevers, night sweats, and weight loss are suggestive of lymphomas, leukemia, or infective endocarditis. A family history of chronic diseases and ancestry play an important role in diagnosing rare genetic causes for splenomegaly, such as Gaucher disease in Ashkenazi Jews. Recent travel to malaria-endemic regions as well as a history of alcohol abuse or IV drug use may direct the diagnostic process.