Asplenia

Asplenia is the physiological absence of splenic function which causes:

Immunocompromise
Most importantly a vulnerability to encapsulated organisms. Infections that occur at an ↑ frequency include:
- S. pneumoniae
  Causes 50-90% of post-splenectomy sepsis.
- H. influenzae type B
- N. meningitidis
- Capnocytophaga canimorsus
- Salmonella
Thrombocytosis

Epidemiology and Risk Factors

Key splenic functions (which are lost) include:

Blood filtration
Exposure of blood to large numbers of phagocytes permits destruction of:
- Opsonised bacteria
  Can also occur in the liver.
- Poorly-opsonised bacteria
  Bacteria not susceptible to complement binding are removed in the spleen.
IgM memory B-cell maintenance
Significant ↓ in number following splenectomy.
Antibody production
Complement production
Haematopoiesis
Site of extramedullary haematopoiesis, which is important in infancy and in bone marrow failure.
Erythrocyte storage
Provides a reserve of red cells that can be recruited into the circulation during exercise or shock.

Bacterial capsules are a polysaccharide envelope that inhibits binding of complement. Encapsulated organisms include:

Causes include:

Splenic remnants may survive in the peritoneum (splenosis), and maintain reasonably normal splenic function.

History:

Exam:

Bedside:

Laboratory:

Blood film
Generally shows a selection of abnormal erythrocytes that would normally be removed by the spleen, including:
- Howel-Jolly bodies
- Target cells
- Pappenheimer bodies

Red cell abnormalities are covered in detail under Erythrocytes.

Imaging:

Other:

Preventative:

Immunocompromise
- Spleen registry referral
- Vaccination
  - Pneumococcal
  - H. influenzae type B
  - Meningococcal
  - Influenza
- Prophylactic antibiotics
Thrombosis
↑ Risk following splenectomy, management options include:
- Aspirin
- Hydroxyurea