The spleen, similar in structure to a large lymph node, acts as a blood filter. Current knowledge of its purpose includes the removal of old red blood cells and platelets, and the detection and fight against certain bacteria. It is also known to function as a site for the development of new red blood cells from their hematopoietic stem cell precursors, and particularly in situations in which the bone marrow, the normal site for this process, has been compromised by a disorder such as leukemia. The spleen is enlarged in a variety of conditions such as malaria, mononucleosis and most commonly in cancers of the lymphatics, such as lymphomas or leukemia.
It is removed under the following circumstances:
- When it becomes very large such that it becomes destructive to platelets/red blood cells
- For diagnosing certain lymphomas
- Certain cases of wandering spleen
- When platelets are destroyed in the spleen as a result of an auto-immune condition, such as idiopathic thrombocytopenic purpura.
- When the spleen bleeds following physical trauma
- Following spontaneous rupture
- For long-term treatment of congenital erythropoietic porphyria (CEP) if severe hemolytic anemia develops
- The spread of gastric cancer to splenic tissue
- When using the splenic artery for kidney revascularisation in renovascular hypertension.
- For long-term treatment of congenital pyruvate kinase (PK) deficiency
The classical cause of traumatic damage to the spleen is a blow to the abdomen during a sporting event. In cases where the spleen is enlarged due to illness (mononucleosis), trivial activities, such as leaning over a counter or straining while defecating, can cause a rupture.
Laparoscopy is the preferred procedure in cases where the spleen is not too large and when the procedure is elective. Open surgery is performed in trauma cases or if the spleen is enlarged. Either method is major surgery and is performed under general anesthesia. Vaccination for pneumococcus, H. influenza and meningococcus should be given pre-operatively if possible to minimize the chance of overwhelming post-splenectomy infection (OPSI), a rapid-developing and potentially fatal type of septicaemia. The spleen is located and disconnected from its arteries. The ligaments holding the spleen in place are dissected and the organ is removed. In some cases, one or more accessory spleens are discovered and also removed during surgery. The incisions are closed and when indicated, a drain is left. If necessary, tissue samples are sent to a laboratory for analysis.
Side effects 
As splenectomy causes an increased risk of sepsis due to encapsulated organisms (such as S. pneumoniae and Haemophilus influenzae) the patient should receive the pneumococcal conjugate vaccine (Prevnar), Hib vaccine, and the meningococcal vaccine; see asplenia. These bacteria often cause a sore throat under normal circumstances but after splenectomy, when infecting bacteria cannot be adequately opsonized, the infection becomes more severe.
An increase in blood leukocytes can occur following a splenectomy. The post-splenectomy platelet count may rise to abnormally high levels (thrombocytosis), leading to an increased risk of potentially fatal clot formation. There also is some conjecture that post-splenectomy patients may be at elevated risk of subsequently developing diabetes. Splenectomy may also lead to chronic neutrophilia. Splenectomy patients typically have Howell-Jolly bodies and less commonly Heinz bodies in their blood smears. Heinz bodies are usually found in cases of G6PD (Glucose-6-Phosphate Dehydrogenase) and chronic liver disease.
Partial splenectomy 
Much of the spleen's protective roles can be maintained if a small amount of spleen can be left behind. Where clinically appropriate, attempts are now often made to perform either surgical subtotal (partial) splenectomy, or partial splenic embolization. In particular, whilst vaccination and antibiotics provide good protection against the risks of asplenia, this is not always available in poorer countries. However as it may take some time for the preserved splenic tissue to provide the full protection, it has been advised that preoperative vaccination still be given.
See also 
- Frye R. (2006-03-02). "Porphyria, Cutaneous". eMedicine. Retrieved 2006-03-28.
- "Guidelines for the prevention and treatment of infection in patients with an absent or dysfunctional spleen. Working Party of the British Committee for Standards in Haematology Clinical Haematology Task Force". BMJ 312 (7028): 430–4. 1996. doi:10.1136/bmj.312.7028.430. PMC 2350106. PMID 8601117.
- J M Davies et al. (2001-06-02). "The Prevention And Treatment Of Infection In Patients With An Absent Or Dysfunctional Spleen - British Committee for Standards in Haematology Guideline up-date". BMJ. Full text.
- http://www.nytimes.com/2004/11/09/health/09diab.html?pagewanted=print&position= New York Times article
- synd/1596 at Who Named It?
- Katcher AL. Familial asplenia, other malformations, and sudden death. Pediatrics. 1980 Mar;65(3):633-5.
- Hematology: Clinical Principles and Applications. Rodak B, Fritsma, G and Doig, K.
- "Anemia in Children - October 15, 2001 - American Family Physician".
- Grosfeld JL, Ranochak JE (1976). "Are hemisplenectomy and/or primary splenic repair feasible?". J. Pediatr. Surg. 11 (3): 419–24. doi:10.1016/S0022-3468(76)80198-4. PMID 957066.
- Bader-Meunier B, Gauthier F, Archambaud F, et al. (2001). "Long-term evaluation of the beneficial effect of subtotal splenectomy for management of hereditary spherocytosis". Blood 97 (2): 399–403. doi:10.1182/blood.V97.2.399. PMID 11154215.
- Pratl B, Benesch M, Lackner H, et al. (2007). "Partial splenic embolization in children with hereditary spherocytosis". Eur J Haematol 80 (1): 76–80. doi:10.1111/j.1600-0609.2007.00979.x. PMID 18028435.
- Sheikha AK, Salih ZT, Kasnazan KH, et al. (October 2007). "Prevention of overwhelming postsplenectomy infection in thalassemia patients by partial rather than total splenectomy". Can J Surg 50 (5): 382–6. PMC 2386178. PMID 18031639.
- Kimber C, Spitz L, Drake D, et al. (1998). "Elective partial splenectomy in childhood". J. Pediatr. Surg. 33 (6): 826–9. doi:10.1016/S0022-3468(98)90651-0. PMID 9660206.