Pathology and causes
On physical examination in adults, the spleen should not be palpable. If it can be palpated, this indicates an enlargement of ≥1.5 times. The degree of spleen enlargement is determined by the distance from its well-defined edge to the left costal margin in centimeters.
Causes:
- infections: bacterial (tuberculosis, typhoid fever and paratyphoid fever, brucellosis, infective endocarditis), viral (infectious mononucleosis, cytomegalovirus, viral hepatitis), protozoan (malaria, toxoplasmosis, leishmaniasis);
- myeloproliferative neoplasms: primary myelofibrosis, chronic myeloid leukemia;
- lymphoproliferative neoplasms: hairy cell leukemia, splenic marginal zone lymphoma, chronic lymphocytic leukemia;
- autoimmune and systemic diseases: rheumatoid arthritis, Felty's syndrome, systemic lupus erythematosus, drug reactions, sarcoidosis, primary and secondary amyloidosis;
- portal hypertension: hepatic cirrhosis, Budd-Chiari syndrome, portal obstruction (thrombosis, narrowing, congenital cavernosity, compression by lymph nodes and tumors) or splenic vein obstruction (thrombosis, narrowing, aneurysm or compression by pancreatic tumors or other neoplasms);
- hemolytic anemias: congenital and acquired (including autoimmune);
- acute leukemia (usually a slight increase);
- accumulation diseases: Gaucher disease, Niemann-Pick disease, mucopolysaccharidosis;
- Other (rare): cysts (congenital, post-traumatic, post-infarction, echinococcal), abscesses, tumor metastases, benign and malignant tumors of the spleen, hemophagocytic lymphohistiocytosis.
An enlarged spleen can be the cause of hypersplenism, that is, sequestration and excessive destruction of blood cells (usually all, although it is limited to 1 or 2 cell lines) by splenic macrophages.
The signs of hypersplenism do not depend on the degree of spleen enlargement. If the enlargement is due to, for example, amyloidosis or tumor metastasis, then hypersplenism is not observed (hyposplenism may be present).
In the case of an enlarged spleen with lymphoproliferative neoplasms, the signs of hypersplenism, even with a large spleen, are not as pronounced as with portal hypertension or Gaucher disease.
Diagnostics
A negative palpation result does not rule out spleen enlargement and hypersplenism. Ultrasound and CT scans can assess spleen size, the presence of focal changes, and additional spleens. Diagnostic testing depends on the suspected underlying disease. Note: If the distance from the well-defined edge of the spleen to the left costal margin is >10 cm (generally the same as crossing the midline of the body), then the most common cause is a hematopoietic system disorder.
Hypersplenism is confirmed by a complete blood count (cytopenia) and a bone marrow aspiration biopsy (increased hematopoiesis). The most reliable test is scintigraphy with a radioactive isotope of technetium, which reveals increased splenic macrophage activity.