An
overwhelming post-splenectomy infection (
OPSI) is a rare but rapidly fatal
infectionAn infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply, usually at the expense of the host. The infecting organism, or pathogen, interferes with the normal functioning of the...
occurring in individuals following removal of the
spleenThe spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells, holds a reserve in case of hemorrhagic shock, especially in...
. The infections are typically characterized by either
meningitisMeningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
or
sepsisSepsis is a serious medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection.
, and are caused by encapsulated organisms including Streptococcus pneumoniaeStreptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, bile soluble aerotolerant anaerobe and a member of the genus Streptococcus. A significant human pathogenic bacterium, S...
.
The risk of OPSI is 0.23-0.42% per year, with a lifetime risk of 5%. Most infections occur in the first few years following splenectomyA splenectomy is a procedure that involves the removal of the spleen by operative means.-Indications:Indications of splenectomy can be divided into general and specific indications. For general indications, they include the following:-Procedure:...
, but the risk of OPSI is lifelong.
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An
overwhelming post-splenectomy infection (
OPSI) is a rare but rapidly fatal
infectionAn infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply, usually at the expense of the host. The infecting organism, or pathogen, interferes with the normal functioning of the...
occurring in individuals following removal of the
spleenThe spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells, holds a reserve in case of hemorrhagic shock, especially in...
. The infections are typically characterized by either
meningitisMeningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
or
sepsisSepsis is a serious medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection.
, and are caused by encapsulated organisms including Streptococcus pneumoniaeStreptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, bile soluble aerotolerant anaerobe and a member of the genus Streptococcus. A significant human pathogenic bacterium, S...
.
The risk of OPSI is 0.23-0.42% per year, with a lifetime risk of 5%. Most infections occur in the first few years following splenectomyA splenectomy is a procedure that involves the removal of the spleen by operative means.-Indications:Indications of splenectomy can be divided into general and specific indications. For general indications, they include the following:-Procedure:...
, but the risk of OPSI is lifelong. OPSI is nearly uniformly fatal without treatment, and modern treatment has decreased the mortality to approximately 40-70%. Individuals with OPSI are most commonly treated with antibioticIn common usage, an antibiotic is a substance or compound that kills or inhibits the growth of bacteria...
s and supportive care. Measures to prevent OPSI include vaccination and prophylactic antibiotics.
Mechanism
The spleenThe spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells, holds a reserve in case of hemorrhagic shock, especially in...
contains many macrophages (part of the reticuloendothelial systemThe reticuloendothelial system , part of the immune system, consists of the phagocytic cells located in reticular connective tissue, primarily monocytes and macrophages. These cells accumulate in lymph nodes and the spleen...
), immune cells which phagocytose (eat) and destroy bacteriaThe bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
. In particular, these macrophages are activated when bacteria are bound by IgG antibodies (IgG1 or IgG3) or complementIn many different fields, the complement of X is something that together with X makes a complete whole—something that supplies what X lacks.Complement may refer to:...
component C3b. These types of antibodies and complement are immune substances called opsonizers, molecules which bind to the surface of bacteria to make them easier for macrophages to phagocytose and destroy the bacteria.
When the spleen is gone, IgG and complement component C3b are still bound to bacteria, but they cannot be removed from the bloodBlood is a specialized bodily fluid that delivers necessary substances to the body's cells — such as nutrients and oxygen — and transports waste products away from those same cells....
circulation because the spleen, which contained the macrophages, is gone. The bacteria therefore are free to cause infectionAn infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host's resources to multiply, usually at the expense of the host. The infecting organism, or pathogen, interferes with the normal functioning of the...
.
Patients without spleens often need immunizationImmunization, or immunisation, is the process by which an individual's immune system becomes fortified against an agent ....
s against pathogenA pathogen , infectious agent, or germ, is a biological agent that causes disease or illness to its host....
s that normally require opsonization and phagocytosis by macrophages in the spleen. These include common human pathogens with capsuleThe word capsule, or encapsulation, may refer to:* Capsule , a cover or envelope partly or wholly surrounding a structure.* Capsule , a type of dry fruit like the poppy, iris or foxglove...
s (Streptococcus pneumoniaeStreptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, bile soluble aerotolerant anaerobe and a member of the genus Streptococcus. A significant human pathogenic bacterium, S...
, Salmonella typhi, Neisseria meningitidisNeisseria meningitidis is a heterotrophic gram-negative diplococcal bacterium best known for its role in meningitis and other forms of meningococcal disease such as meningococcemia. N...
, E. coli, Hemophilus influenzae, Streptococcus agalactiaeStreptococcus agalactiae is a beta-hemolytic gram-positive streptococcus.-Identification:...
, Klebsiella pneumoniaeKlebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines. It is clinically the most important member of the Klebsiella genus of Enterobacteriaceae; it is closely...
). Capsules ( made of polysaccharidePolysaccharides are polymeric carbohydrate structures, formed of repeating units joined together by glycosidic bonds. These structures are often linear, but may contain various degrees of branching. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit...
s [sugars]) are an evolutionary development by bacteria to evade phagocytosisPhagocytosis is the cellular process of phagocytes and protists of engulfing solid particles by the cell membrane to form an internal phagosome...
by macrophageMacrophages are white blood cells within tissues, produced by the division of monocytes. Human macrophages are about in diameter...
s alone, since only proteinProteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues...
s are directly recognized by macrophages in phagocytosis. Humoral immunity in the form of IgG and complement proteins is the answer of the human immune system to allow these pathogens marked for destruction.