Asplenia

This article is about the medical condition. For the moth genus, see Armadini. For spleenwort ferns, see Asplenium.

Asplenia refers to the absence ('a-') of normal spleen function and is associated with some serious infection risks. Hyposplenism is used to describe reduced ('hypo-') splenic functioning, but not as severely affected as with asplenism.

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Causes

• Congenital asplenia (rare) may be due to genetic disorders, heterotaxy syndrome, or exposure to environmental factors during gestation.^[1]
• Acquired asplenia occurs for several reasons:
  • After splenectomy (surgical removal) e.g. after splenic rupture from trauma or because of tumor
  • After splenectomy with the goal of interfering with splenic function, as a treatment for diseases (e.g. ITP, thalessemia, spherocytosis) where the spleen's usual activity exacerbates the disease
  • Due to underlying diseases that destroy the spleen (autosplenectomy), e.g. sickle-cell disease.
• Functional asplenia occurs when splenic tissue is present but does not work well, e.g. sickle-cell disease, polysplenia; these patients are managed as if asplenic.

Partial splenectomy preservation of splenic function

In an effort to preserve some of the spleen's protective roles,^[2] attempts are now often made to preserve a small part of the spleen when performing either surgical subtotal (partial) splenectomy,^[3] or partial splenic embolization.^[4] This may be particularly important in poorer countries where protective measures for patients with asplenia are not available.^[5] However it has been advised that preoperative vaccination is advisable until the remnant splenic tissue can reestablish its function.^[6]

Risks

Asplenia increases the risk of septicaemia from encapsulated bacteria, and can result in a syndrome known as overwhelming post splenectomy infection (OPSI) which can kill within a few hours. In particular, patients are at risk from Pneumococcus, Haemophilus influenzae, and meningococcus. The risk is elevated as much as 350-fold.^[7]

The risk to asplenic patients has been expressed as equivalent for a child to die in home accident, and for adults dying in a road traffic accident (reference UK Splenectomy Trust Advice) - so sensible precautions are needed, but no panic.^[8]

Management

To minimise the risks, antibiotic & vaccination protocols have been established,^[9][10] but are often poorly adhered to by doctors and patients.^[11]

Antibiotic prophylaxis

Because of the increased risk of infection, physicians administer oral antibiotics as a prophylaxis after a surgical splenectomy (or starting at birth, for congenital asplenia or functional asplenia). The duration suggested varies: one suggestion is that antibiotics be taken for two years or until the age of sixteen years old is reached, whichever is longer.

Patients are also cautioned to start a full-dose course of antibiotics at the first onset of an upper or lower respiratory tract infection (for example, sore throat or cough), or at the onset of any fever.

Vaccinations

It is suggested that splenectomized persons receive the following vaccinations, and ideally prior to planned splenectomy surgery:

• Pneumococcal polysaccharide vaccine (not before 2 years of age). Children may first need one or more boosters of pneumococcal conjugate vaccine if they did not complete the full childhood series.
• Haemophilus influenzae type b vaccine, especially if not received in childhood. For those adults who have not been previously vaccinated, two doses given two months apart were advised in the new 2006 UK vaccination guidelines (in the UK may be given as a combined Hib/MenC vaccine).^[12]
• Meningococcal conjugate vaccine, especially if not received in adolescence. Previously vaccinated adults require a single booster and non-immunised adults advised, in UK since 2006, to have two doses given two months apart.^[12] Children too young for the conjugate vaccine should receive meningococcal polysaccharide vaccine in the interim.^[7]
• Influenza vaccine, every winter, to help prevent getting secondary bacterial infection.

Travel measures

In addition to the normal immunisations advised for the countries to be visited, Group A meningococcus should be included if visiting counties of particular risk (e.g. sub-saharan Africa). The non-conjugated Meningitis A&C vaccines usually used for this purpose give only 3 years coverage and provide less-effective long-term cover for Meningitis C than the conjugated form already mentioned.

Those lacking a functional spleen are at higher risk of catching malaria and dying from this. Travel to malarial areas will carry greater risks and may be best avoided. Travellers should take the most appropriate anti-malarial prophylaxis medication and be extra vigilant over measures to prevent mosquito bites.

The pneumococcal vaccinations may not cover some of the other strains of pneumococcal bacteria present in other countries. Likewise their antibiotic resistance may also vary, requiring a different choice of stand-by antibiotic.

Additional measures

• Surgical and Dental procedures - Antibiotic prophylaxis may be required before certain surgical or dental procedures.
• Animal bites - adequate antibiotic cover is required after even minor dog or other animal bites. Asplenic patients are particularly susceptible to infection by C. canimorsus and should receive a five day course of co-amoxiclav (erythromycin in patients allergic to penicillin).^[13]
• Tick bites - Babesiosis is a rare tickborne infection. Patients should check themselves or have themselves inspected for tick bites if they are in an at-risk situation. Presentation with fever, fatigue, and haemolytic anaemia requires diagnostic confirmation by identifying the parasites within red blood cells on blood film and by specific serology. Quinine (with or without clindamycin) is usually an effective treatment.^[13]
• Alert warning - Consider carrying a card, or wearing a special bracelet or necklet which says that you do not have a working spleen. This would alert a doctor to take rapid action if you are seriously ill and cannot tell them yourself.