Asplenia/Hyposplenia The 5 Minute Pediatric Consult
Barbara Haber
DEFINITION
Hyposplenia and asplenia are defined by the
functional capacity of the spleen to filter blood and perform immunogenic
functions.
PATHOPHYSIOLOGY
- Hyposplenia/asplenia occurs in association with a number of illnesses and
after splenectomy.
- Most patients with hyposplenism process antigens without difficulty.
- If the spleen is minimally functional, an inability to handle infections
results from defective antibody synthesis and removal of opsonized organisms.
- Encapsulated microorganisms, such as Pneumococcus, Meningococcus,
and Haemophilus, are usually handled by this mechanism.
- Under the age of 4 years, significant morbidity and mortality can result
for the patient with impaired splenic function.
However, the asplenia syndrome should be viewed
separately. Asplenia syndrome is characterized by complex congenital heart
disease, asplenia, and abdominal heterotaxy. Common associated anomalies include
atrioventricular canal defects, conotruncal anomalies, anomalous systemic
pulmonary venous connections, and visceroatrial situs inversus. Its morbidity is
distinctly unfavorable.
GENETICS
- Most causes of hyposplenia or asplenia are not inherited.
- A disturbance in embryogenesis in the fifth week of gestation results in
bilateral right-sidedness with abnormal pulmonary lobation in 80% of patients
and abdominal heterotaxy in 72%. An autosomal recessive inheritance pattern is
suggested based on family studies and mouse models of heterotaxy. A review of
519 autopsy cases calculated survival to be 2.6 months, with death typically
resulting from cardiorespiratory failure or infection.
Diminished splenic function is found
in/with:
- Normal infants
- Congenital asplenia
- Asplenia syndrome
- Old age
- Sequestration crises (sickle cell hemoglobinopathies, essential
thrombocytosis, malaria, thrombosis of the splenic vessels)
- Autoimmune disorders (glomerulonephritis, systemic lupus erythematosus,
rheumatoid arthritis, graft-versus-host disease, and sarcoidosis)
- Gastrointestinal disorders (celiac disease [30%–50% are hyposplenic],
Crohn disease, ulcerative colitis, dermatitis herpetiformis)
- Space-occupying lesions (tumors, amyloid, cysts)
- Splenic irradiation
- Postsplenectomy
HISTORY
- Has there been an underlying disease such as sickle cell disease or Crohn
disease?
- Is there a history of recurrent fevers?
- Physical examination may reveal that the spleen may be normal, large, or
atretic and cannot be used as an index of splenic function.
- The size of the spleen is most closely linked to the underlying etiology.
- Complete splenic replacement by cysts, neoplasm, or amyloid are examples
of hyposplenic splenomegaly.
- Sequestration crises such as that associated with sickle cell disease and
malaria clog the spleen with cellular debris, resulting in an increased spleen
size and decreased function.
- In the apparently healthy child with no identified risk factors who
presents with an overwhelming infection with an encapsulated organism, the
hematologic smear should be examined.
- Reduction or absence of splenic function can be determined by specific
hematologic changes.
- Nonspecific changes include a modest increase in WBC and platelet count.
Target cells, Howell-Jolly bodies (nuclear fragments that normally are removed
in the spleen), and pitted erythrocytes can be visualized on peripheral blood
smear.
- Pits or pox on the red-cell surface are the most sensitive indicator of
hyposplenism.
- These are submembranous vacuoles that can be seen only in wet
preparations of red cells using direct interference–contrast
microscopy.
- 51Cr-labeled, heat-damaged red blood cells
can be used to measure the capacity of the spleen to clear particulate matter
from the bloodstream.
- The size of the spleen can be determined by either ultrasound or computed
tomography (CT) scan.
- Immunization with a polyvalent pneumococcal vaccine should be carried out
in all patients with hyposplenism.
- Those who will be undergoing splenectomy should receive the vaccine prior
to the operation.
- No revaccination is needed according to the present recommendations.
- Children should also receive Haemophilus influenzae
vaccine.
PITFALLS
Under the age of 4 years, splenectomy is
contraindicated because of the risk of developing bacterial
infection.
| COMMON QUESTIONS
AND ANSWERS |
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|
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Q: What should I do if my child has a
fever?
A: In hyposplenic patients, especially those under the age of 4
years, all fevers should be taken seriously. If the child is not on prophylactic
penicillin, he/she should be treated for all symptomatic infections.
Q: Are there any special times I need to worry
about infections?
A: In these patients, dental work, especially tooth
extraction, should always be preceded by a course of prophylactic
antibiotics.
ICD-9-CM 459.0
Phoon CK, Neill CA. Asplenia syndrome: insight into
embryology through an analysis of cardiac and extracardiac anomalies. Am J
Cardiol 1994;73:581–587.
Phoon CK, Neill CA. Asplenia syndrome—risk factors
for early unfavorable outcome. Am J Cardiol 1994;73:1235–1237.
Copyright
© 2000 Lippincott Williams & Wilkins
M. William
Schwartz, Louis M. Bell, Jr., Peter M. Bingham, Esther K. Chung, David F.
Friedman and Andrew E. Mulberg, The 5 Minute Pediatric Consult