An autosplenectomy (from" 'auto-' "self," '-splen-' "spleen," '-ectomy' "removal) is a negative outcome of disease and occurs when a disease damages the spleen to such an extent that it becomes shrunken and non-functional. The spleen is an important immunological organ that acts as a filter for red blood cells, triggers phagocytosis of invaders, and mounts an immunological response when necessary. Lack of a spleen, called asplenia, can occur by autosplenectomy or the surgical counterpart, splenectomy. Asplenia can increase susceptibility to infection. Autosplenectomy can occur in cases of sickle-cell disease where the misshapen cells block blood flow to the spleen, causing fibrosis and eventual atrophy of the organ. Autosplenectomy is a rare condition that is linked to certain diseases but is not a common occurrence.

The most frequent cause of autosplenectomy is sickle cell anemia which causes progressive splenic hypofunction over time. Increased deoxygenation causes sickling of red blood cells, which adhere to the spleen wall and splenic macrophages causing ischemia. This ischemia can result in splenic sequestration, where large amounts of blood pool in the spleen but do not flow within vasculature. This lack of blood flow can cause atrophy in the spleen and can lead to autosplenectomy.

Enlargement of the spleen is known as splenomegaly. It may be caused by sickle cell anemia, sarcoidosis, malaria, bacterial endocarditis, leukemia, 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), 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 diseases include splenomegaly, where the spleen is enlarged for various reasons. On the other hand, a lack of normal spleen function is called asplenia.

Splenic infarction is a condition in which oxygen supply to the spleen is interrupted, leading to partial or complete infarction (tissue death due to oxygen shortage) in the organ.

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. It has to be differentiated from other causes of acute abdomen.

An abdominal CT scan is the most commonly used modality to confirm the diagnosis, although abdominal ultrasound can also contribute.

There is no specific treatment, except treating the underlying disorder and providing adequate pain relief. Surgical removal of the spleen (splenectomy) is only required if complications ensue; surgical removal predisposes to overwhelming post-splenectomy infections.

In one series of 59 patients, mortality amounted to 5%. Complications include a ruptured spleen, bleeding, an abscess of the spleen (for example, if the underlying cause is infective endocarditis) or pseudocyst formation. Splenectomy may be warranted for persistent pseudocysts due to the high risk of subsequent rupture.

Several factors may increase the tendency for clot formation, such as specific infections (such as infectious mononucleosis, cytomegalovirus infection, malaria, or babesiosis), inherited clotting disorders (thrombophilia, such as Factor V Leiden, antiphospholipid syndrome), malignancy (such as pancreatic cancer) or metastasis, or a combination of these factors.

In some conditions, blood clots form in one part of the circulatory system and then dislodge and travel to another part of the body, which could include the spleen. These emboligenic disorders include atrial fibrillation, patent foramen ovale, endocarditis or cholesterol embolism.

Splenic infarction is also more common in hematological disorders with associated splenomegaly, such as the myeloproliferative disorders. Other causes of splenomegaly (for example, Gaucher disease or hemoglobinopathies) can also predispose to infarction. Splenic infarction can also result from a sickle cell crisis in patients with sickle cell anemia. Both splenomegaly and a tendency towards clot formation feature in this condition. In sickle cell disease, repeated splenic infarctions lead to a non-functional spleen (autosplenectomy).

Any factor that directly compromises the splenic artery can cause infarction. Examples include abdominal traumas, aortic dissection, torsion of the splenic artery (for example, in wandering spleen) or external compression on the artery by a tumor. It can also be a complication of vascular procedures.

Splenic infarction can be due to vasculitis or disseminated intravascular coagulation. Various other conditions have been associated with splenic infarction in case reporters, for example granulomatosis with polyangiitis or treatment with medications that predispose to vasospasm or blood clot formation, such as vasoconstrictors used to treat esophageal varices, sumatriptan or bevacizumab.