Clinical significance
Thalassemia enlarged spleen taken after splenectomy
Enlarged spleen
Main article: Splenomegaly
Enlargement of the spleen is known as splenomegaly. It may be caused by sickle cell anemia, sarcoidosis, malaria, bacterial endocarditis, leukemia, polycythemia vera, pernicious anemia, Gaucher's disease, leishmaniasis, Hodgkin's disease, Banti's disease, hereditary spherocytosis, cysts, glandular fever (mononucleosis or 'Mono' caused by the Epstein–Barr virus, infection from cytomegalovirus), and tumours. Primary tumors of the spleen include hemangiomas and hemangiosarcomas. Marked splenomegaly may result in the spleen occupying a large portion of the left side of the abdomen.
The spleen is the largest collection of lymphoid tissue in the body. It is normally palpable in preterm infants, in 30% of normal, full-term neonates, and in 5% to 10% of infants and toddlers. A spleen easily palpable below the costal margin in any child over the age of 3–4 years should be considered abnormal until proven otherwise.
Splenomegaly can result from antigenic stimulation (e.g., infection), obstruction of blood flow (e.g., portal vein obstruction), underlying functional abnormality (e.g., hemolytic anemia), or infiltration (e.g., leukemia or storage disease, such as Gaucher's disease). The most common cause of acute splenomegaly in children is viral infection, which is transient and usually moderate. Basic work-up for acute splenomegaly includes a complete blood count with differential, platelet count, and reticulocyte and atypical lymphocyte counts to exclude hemolytic anemia and leukemia. Assessment of IgM antibodies to viral capsid antigen (a rising titer) is indicated to confirm Epstein–Barr virus or cytomegalovirus. Other infections should be excluded if these tests are negative.
Splenic injury
Main article: Splenic injury
Trauma, such as a road traffic collision, can cause rupture of the spleen, which is a situation requiring immediate medical attention.
Asplenia
Main article: Asplenia
Asplenia refers to a non-functioning spleen, which may be congenital, or caused by traumatic injury, surgical resection (splenectomy) or a disease such as sickle cell anaemia. Hyposplenia refers to a partially functioning spleen. These conditions may cause[6] a modest increase in circulating white blood cells and platelets, a diminished response to some vaccines, and an increased susceptibility to infection. In particular, there is an increased risk of sepsis from polysaccharide encapsulated bacteria. Encapsulated bacteria inhibit binding of complement or prevent complement assembled on the capsule from interacting with macrophage receptors. Phagocytosis needs natural antibodies, which are immunoglobulins that facilitate phagocytosis either directly or by complement deposition on the capsule. They are produced by IgM memory B cells (a subtype of B cells) in the marginal zone of the spleen.[22][23]
A splenectomy (removal of the spleen) results in a greatly diminished frequency of memory B cells.[24] A 28-year follow-up of 740 World War II veterans whose spleens were removed on the battlefield showed a significant increase in the usual death rate from pneumonia (6 rather than the expected 1.3) and an increase in the death rate from ischemic heart disease (41 rather than the expected 30), but not from other conditions.[25]
Accessory spleen
An accessory spleen is a small splenic nodule extra to the spleen usually formed in early embryogenesis. Accessory spleens are found in approximately 10 percent of the population[26] and are typically around 1 centimeter in diameter. Splenosis is a condition where displaced pieces of splenic tissue (often following trauma or splenectomy) autotransplant in the abdominal cavity as accessory spleens.[27]
Polysplenia is a congenital disease manifested by multiple small accessory spleens,[28] rather than a single, full-sized, normal spleen. Polysplenia sometimes occurs alone, but it is often accompanied by other developmental abnormalities such as intestinal malrotation or biliary atresia, or cardiac abnormalities, such as dextrocardia. These accessory spleens are non-functional.
Infarction
Main article: Splenic infarction
Splenic infarction is a condition in which blood flow supply to the spleen is compromised,[29] leading to partial or complete infarction (tissue death due to oxygen shortage) in the organ.[30]
Splenic infarction occurs when the splenic artery or one of its branches are occluded, for example by a blood clot. Although it can occur asymptomatically, the typical symptom is severe pain in the left upper quadrant of the abdomen, sometimes radiating to the left shoulder. Fever and chills develop in some cases.[31] It has to be differentiated from other causes of acute abdomen.
Hyaloserositis
The spleen may be affected by hyaloserositis, in which it is coated with fibrous hyaline.[32][33]