Editing Spleen (section)

== Clinical significance ==
[[File:Spleen after spleenectomy.jpg|alt=Surgically removed spleen of a child with thalassemia. It is about 15 times larger than normal.|thumb|[[Thalassemia]]-enlarged spleen taken after [[splenectomy]]]]

=== Enlarged spleen ===
{{Main|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 syndrome|Banti's disease]], [[hereditary spherocytosis]], [[cyst]]s, glandular fever (including [[Infectious mononucleosis|mononucleosis]] or 'Mono' caused by the [[Epstein–Barr virus]] and infection from [[Human betaherpesvirus 5|cytomegalovirus]]), and [[tumour]]s. Primary tumors of the spleen include [[hemangioma]]s and [[hemangiosarcoma]]s. 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 three to four 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 [[Human betaherpesvirus 5|cytomegalovirus]]. Other infections should be excluded if these tests are negative.

Calculators have been developed for measurements of spleen size based on [[CT scan|CT]], [[Ultrasound|US]], and [[Magnetic resonance imaging|MRI]] findings.

=== Splenic injury ===
{{Main|Splenic injury}}
[[trauma (medicine)|Trauma]], such as a [[traffic collision|road traffic collision]], can cause [[ruptured spleen|rupture of the spleen]], which is a situation requiring immediate medical attention.

=== Asplenia ===
{{Main|Asplenia}}

[[Asplenia]] refers to a non-functioning spleen, which may be [[genetic disorder|congenital]], or caused by traumatic injury, surgical resection ([[splenectomy]]) or a disease such as [[Sickle cell disease|sickle cell anaemia]]. Hyposplenia refers to a partially functioning spleen. These conditions may cause<ref name="Jia"/> a modest increase in circulating [[white blood cell]]s and [[platelet]]s, a diminished response to some [[vaccine]]s, 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 [[immunoglobulin M|IgM]] [[memory B cell]]s (a subtype of [[B cell]]s) in the [[marginal zone]] of the spleen.<ref>{{cite journal|last=Di Sabatino|first=A|author2=Carsetti, R |author3=Corazza, GR |title=Post-splenectomy and hyposplenic states|journal=Lancet|date=Jul 2, 2011|volume=378|issue=9785|pages=86–97|pmid=21474172|doi=10.1016/S0140-6736(10)61493-6|s2cid=30554953}}</ref><ref>{{cite journal|last=Carsetti|first=R|author2=Rosado, MM |author3=Wardmann, H |title=Peripheral development of B cells in mouse and man|journal=Immunological Reviews|date=February 2004|volume=197|pages=179–91|pmid=14962195|doi=10.1111/j.0105-2896.2004.0109.x|s2cid=20654498}}</ref>

A [[splenectomy]] (removal of the spleen) results in a greatly diminished frequency of memory B cells.<ref>{{cite journal|last=Kruetzmann|first=S |author2=Rosado, MM |author3=Weber, H |author4=Germing, U |author5=Tournilhac, O |author6=Peter, HH |author7=Berner, R |author8=Peters, A |author9=Boehm, T |author10=Plebani, A |author11=Quinti, I |author12=Carsetti, R|title=Human immunoglobulin M memory B cells controlling Streptococcus pneumoniae infections are generated in the spleen|journal=The Journal of Experimental Medicine|date=Apr 7, 2003|volume=197|issue=7|pages=939–45|pmid=12682112|doi=10.1084/jem.20022020|pmc=2193885}}</ref> 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.<ref>{{Cite journal|pmid=69206|doi=10.1016/S0140-6736(77)90132-5|title=Splenectomy and Subsequent Mortality in Veterans of the 1939–45 War|year=1977|last1=Dennis Robinette|first1=C.|last2=Fraumeni|first2=Josephf.|journal=The Lancet|volume=310|issue=8029|pages=127–29|s2cid=38605411}}</ref>

=== Accessory spleen ===
An [[accessory spleen]] is a small splenic nodule extra to the spleen usually formed in early [[human embryogenesis|embryogenesis]]. Accessory spleens are found in approximately 10 percent of the population<ref name=klmoore>{{cite book | last = Moore | first = Keith L. | author-link = Keith L. Moore | title = Clinically Oriented Anatomy | edition = 3rd | year = 1992 | publisher = Williams & Wilkins | location = Baltimore | isbn = 978-0-683-06133-8 | page = 187}}</ref> and are typically around 1 centimeter in diameter. ''[[Splenosis]]'' is a condition where displaced pieces of splenic tissue (often following [[physical trauma|trauma]] or splenectomy) [[autotransplantation|autotransplant]] in the abdominal cavity as accessory spleens.<ref>{{cite journal | author = Abu Hilal M |author2=Harb A|author3=Zeidan B|author4=Steadman B|author5=Primrose JN|author6= Pearce NW | date = January 5, 2009 | title = Hepatic splenosis mimicking HCC in a patient with hepatitis C liver cirrhosis and mildly raised alpha feto protein; the important role of explorative laparoscopy | journal = World Journal of Surgical Oncology | volume = 7 | issue = 1 | pmid = 19123935 | pmc = 2630926 | doi = 10.1186/1477-7819-7-1
| page = 1 |doi-access=free }}</ref>

[[Polysplenia]] is a congenital disease manifested by multiple small accessory spleens,<ref>{{DorlandsDict|seven/000085247|polysplenia}}</ref> 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|Splenic infarction}}

[[Splenic infarction]] is a condition in which blood flow supply to the spleen is compromised,<ref name="Chapman Bhimji 2018 p.">{{citation | last1=Chapman | first1=J | last2=Bhimji | first2=SS | title=Splenic Infarcts | chapter=article-29380 | publisher=StatPearls Publishing | location=Treasure Island (FL) | year=2018 | pmid=28613652 | url=http://www.ncbi.nlm.nih.gov/books/NBK430902/ | access-date=2019-02-27 }}</ref> leading to partial or complete [[infarction]] (tissue death due to oxygen shortage) in the organ.<ref name="pmid3764696">{{cite journal |vauthors=Jaroch MT, Broughan TA, Hermann RE |title=The natural history of splenic infarction |journal=Surgery |volume=100 |issue=4 |pages=743–50 |date=October 1986 |pmid=3764696 }}</ref>

Splenic infarction occurs when the [[splenic artery]] or one of its branches are occluded, for example by a [[blood clot]]. Although it can occur [[asymptomatic]]ally, the typical symptom is severe [[abdominal pain|pain]] in the [[left upper quadrant (abdomen)|left upper quadrant of the abdomen]], sometimes radiating to the left shoulder. Fever and chills develop in some cases.<ref>{{Cite journal |last1=Nores |first1=M1 |last2=Phillips |first2=EH |last3=Morgenstern |first3=L |last4=Hiatt |first4=JR |date=February 1998 |title=The Clinical Spectrum of Splenic Infarction |journal=[[The American Surgeon]] |volume=64 |issue=2 |pages=182–88 |pmid=9486895}}</ref> 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 [[fibrosis|fibrous]] [[hyaline]].<ref name=omd>[http://cancerweb.ncl.ac.uk/cgi-bin/omd?hyaloserositis "Hyaloserositis"]. ''Online Medical Dictionary''. Accessed on: June 21, 2008.</ref><ref>{{cite web |url=https://www.drugs.com/dict/sugar-coated-spleen.html |title=Sugar-coated spleen |publisher=Drugs.com }}</ref>