DESCRIPTION

• Asplenia is the absence of the spleen due to either a congenital anomaly or a surgical procedure.
• Hyposplenia is the reduced or absent function of the spleen, impairing the capacity to prevent bacterial infections.

EPIDEMIOLOGY

• The exact incidence is not known.
• Asplenia is present in about 3% of neonates with structural heart disease.
• Isolated asplenia is most often recognized at autopsy.

PATHOPHYSIOLOGY

• The spleen is a major component of the reticuloendothelial system; it is important both for antibody synthesis and for clearance of opsonized organisms by phagocytosis.
• Antibody-mediated phagocytosis is the primary mechanism to destroy encapsulated microbes, such as pneumococcus, meningococcus, and Haemophilus.
• In the absence of the spleen’s phagocytic pathway, the polysaccharide-rich capsules of these bacteria protect them from destruction and permit them to effect systemic bacterial infection that may lead to overwhelming sepsis.
• For patients <4 years of age in whom few alternate routes of bacterial clearance exist, significant pathology can result from impaired splenic function.

ETIOLOGY

• Surgical splenectomy
• Congenital asplenia
• In association with certain diseases or conditions (see “Differential Diagnosis”)

ASSOCIATED-CONDITIONS

• Besides splenectomy, when asplenia is known, patients with certain diseases are at risk of asplenia or hyposplenia (see “Differential Diagnosis”).
• Asplenia or hyposplenia should be suspected in any patient with overwhelming infection with an encapsulated organism.

HISTORY

• Any patient with a condition known to be associated with asplenia/hyposplenia (see “Differential Diagnosis”) deserves evaluation for splenic function.
• In the apparently healthy child with no identified risk factors who presents with an overwhelming infection with an encapsulated organism, a blood smear should be examined for signs of hyposplenism (see “Initial Tests (screening, lab, imaging)”).

PHYSICAL-EXAM

• The spleen may be normal, large, or nonpalpable. Therefore, the size of the spleen cannot be used as an indicator of splenic function.
• The size is most closely linked to the underlying etiology.
  • Portal hypertension or complete splenic replacement by cysts, neoplasm, or amyloid can lead to splenomegaly.
  • Sequestration crises such as those associated with sickle cell disease and malaria clog the spleen with cellular debris, which may also result in increased spleen size.
  • Patients with sickle cell disease typically have splenomegaly early in life, as the spleen tends to sequester the abnormal red cells. With time, the spleen slowly autoinfarcts and eventually becomes nonpalpable.

DIFF-DIAGNOSIS

Diminished splenic function is associated with the following:

• Congenital
  • Isolated congenital asplenia
  • Heterotaxy syndrome
• Hematologic
  • Sequestration crises (e.g., sickle hemoglobinopathies, essential thrombocytosis, malaria)
  • Sickle cell disease
  • Hereditary hemoglobinopathies
• Autoimmune
  • Glomerulonephritis
  • Systemic lupus erythematosus
  • Rheumatoid arthritis
  • Sarcoidosis
  • Sjögren syndrome
  • Graves disease
  • Graft-versus-host disease
• GI/hepatic
  • Celiac disease
  • Inflammatory bowel disease
  • Chronic liver disease/portal hypertension
• Space-occupying lesions
  • Tumors, such as lymphoma
  • Amyloidosis
  • Cysts
• Postsplenectomy
  • Trauma
  • β-Thalassemia
  • Hereditary spherocytosis
• Vascular
  • Splenic artery occlusion
  • Splenic vein thrombosis
• Miscellaneous
  • Normal infants
  • Elderly
  • Bone marrow transplant
  • HIV infection
• Splenic irradiation

TESTS

GENERAL-MEASURES

• Immunization with pneumococcal, meningococcal, and Haemophilus vaccines should be carried out in all patients with asplenia/hyposplenia.
• In those patients who will be undergoing a scheduled splenectomy, the pneumococcal, meningococcal, and Haemophilus vaccines should be given at least 14 days prior to the operation.
• All children between 6 weeks and 59 months of age should receive the 4-dose series of the 13-valent pneumococcal conjugate vaccine (PCV13).
  • In children 2 to 5 years of age with asplenia/hyposplenia, the 23-valent pneumococcal polysaccharide vaccine (PPSV23) should be administered following the 4-dose series of PCV13.
  • A repeat of the PPSV23 should be administered 5 years after the initial dose.
• Infants between 2 and 23 months of age with asplenia/hyposplenia should receive a 4-dose series of the meningococcal groups C and Y, Haemophilus influenzae b, and tetanus toxoid conjugate vaccine (Hib-MenCY-TT) or the meningococcal groups A, C, W, and Y and diphtheria protein CRM (MenACWY-CRM).
  • Children >19 months should wait until 2 years of age and then receive the 2-dose series of the quadrivalent meningococcal conjugate vaccine with diphtheria toxoid (MenACWY-D).
  • Children should receive first booster of either MenACWY-CRM or MenACWY-D 3 years after completion of primary series.
  • Revaccination is recommended every 5 years (MenACWY-CRM or MenACWY-D).
  • Vaccination against serogroup B for adolescents and young adults is recommended by the Centers for Disease Control and Prevention (CDC).
• Children should also receive the H. influenzae type b vaccine if not completed as above.
• Antimicrobial prophylaxis should be strongly considered in all children with asplenia/hyposplenia.
  • Penicillin or amoxicillin is most commonly used; however, with increasing penicillin resistance, it may be replaced by amoxicillin-clavulanic acid, fluoroquinolones, or cefuroxime.
• Patients with sickle cell disease have impaired splenic function at all stages and should receive antimicrobial prophylaxis.

IN-PATIENT-CONSIDERATIONS

Any patient with asplenia/hyposplenia with a febrile illness should be evaluated for systemic bacterial illness. Blood culture with broad-spectrum antibiotic coverage should be strongly considered.

PATIENT-TEACHING

• Patients should be counseled regarding the risk of bacterial infection and considerations in setting of febrile illness.
• MedicAlert bracelets/necklaces can be used to indicate splenic function and risk of sepsis.

COMPLICATIONS

Bacteremia

• For asplenic or hyposplenic patients, risk of bacteremia is highest in younger children and in the years immediately following splenectomy.
• The most common pathogens causing bacteremia are the encapsulated organisms, Streptococcus pneumoniae, H. influenzae, and Neisseria meningitidis.
• There is also an increased risk of infection with Babesia microti and Plasmodium falciparum (intraerythrocytic parasites) and Capnocytophaga canimorsus (via dog bites).

ICD9

• 759.0 Anomalies of spleen
• V45.79 Other acquired absence of organ
• 289.59 Other diseases of spleen

ICD10

• Q89.01 Asplenia (congenital)
• Z90.81 Acquired absence of spleen
• D73.89 Other diseases of spleen

SNOMED

• 93030006 Congenital absence of spleen (disorder)
• 23761004 Hyposplenism (disorder)