Pediatric Clinics of North America - CIPERJ

PARTIAL SPLENECTOMY FOR HEREDITARY SPHEROCYTOSIS
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splenomegaly [1]. The major disadvantage of total splenectomy, however, in
this setting is the concern for developing overwhelming postsplenectomy
infection (OPSI), which is sepsis from encapsulated bacterial organisms
and often is fatal, particularly in young children. Unfortunately, total splenectomy
occasionally is recommended erroneously for young children who
have a mild clinical phenotype.
Contrary to the common misconception that total splenectomy rarely is
used in children who have HS, the incidence and public health impact of
children who have HS requiring total splenectomy is substantial. The
2003 Healthcare Cost and Utilization Project (HCUP) Kids Inpatient Database,
a robust and widely used measure of pediatric disorders, demonstrated
that the number of children who have HS ages 0 to17 who received total
splenectomy was estimated at 373 children per year (HCUP Kids’ Inpatient
Database, International Classification of Diseases, Ninth Revision, Clinical
Modification category) [22]. In addition to HS, total splenectomy is performed
in children for a variety of other indications, including other hematologic
disorders, such as sickle cell anemia or thalassemia, trauma, and
various acquired illnesses. In children less than 18 years of age, nearly
2000 splenectomy procedures are performed annually in the United States,
with aggregate hospital charges (a ‘‘national bill’’) for these procedures
exceeding $71,000,000 annually [22].
Considering the high incidence and potentially serious complications associated
with total splenectomy in children, the routine use of splenectomy
in children who have HS has an extensive financial and public health impact.
Therefore, examination of alternative surgical approaches, such as partial
splenectomy, has important and widespread implications for improving
the clinical care of children who have hematologic disorders, such as HS.
Immunologic complications of splenectomy and role of memory B cells
Total splenectomy leads to a wide range of immunologic deficits and
complications. The role of the spleen in protecting against infections is
based on complex and interrelated phagocytic and immune functions,
including filtration and phagocytosis of bacteria from the blood, removal
of foreign material, and production of opsonins: antigen-specific IgM, alternate
complement components, properdin, and tuftsin [23]. Therefore, an
intact and functioning spleen seems to have critical protective effects against
common childhood infections. Given the complexity of splenic-dependent
and splenic-independent immune responses involved in bacterial clearance,
determining whether or not and how much immune function is preserved
after partial splenectomy is essential before widespread acceptance of this
procedure.
Recently, a population of surface IgM bright IgD dull CD22 þ CD27 þ human
peripheral blood B cells, termed IgM memory B cells, has been described
that is similar to the murine B-1a B-cell subset producing natural antibodies