Overwhelming postsplenectomy infectionD73.0

King and Shumacker 1952

Overwhelming postsplenectomy infection is a rare condition but is associated with a high mortality. It is defined as septicemia and/or meningitis that is usually fulminant but not necessarily fatal. The prevalence of OPSI has increased recently because splenectomy was a clinically effective treatment for hepatitis C virus-associated thrombocytopenia before the introduction of interferon/ribavirin combination therapy. The interval between splenectomy and onset of OPSI ranges from less than 1 week to more than 20 years.

Splenectomized patients pose a significant risk of infection because the spleen is the largest collection of lymphoid tissue in the body. Excessive postplenectomy infection (OPSI) is a serious fulminant process that has a high mortality rate (Styrt B 1990; Lortan JE 1993).

Important factors in stratifying risk include the age at which splenectomy is performed, the subsequent time interval after splenectomy, the reason for splenectomy, and the overall immune status of the patient REF. Infants acquire specific antibodies to encapsulated organisms relatively late in the development of antibody responses. It is recommended that all asplenic patients receive optimal counseling regardless of the underlying etiology as well as protection from OPSI, as the increased risk of severe sepsis after splenectomy has been shown to be lifelong (White BP et al (1991).

Splenectomy due to hematologic disease, including thalassemia, hereditary spherocytosis, autoimmune hemolysis, immune thrombocytopenic purpura, or lymphoma, appears to carry a higher risk for OPSI than splenectomy due to trauma (Weintraub LR 1994). In addition, patients with hematologic and autoimmune diseases or lymphoma have impaired immunity, and patients undergoing treatment such as chemotherapy often show decreased serum immunoglobulin levels.

Protein-energy malnutrition (PEM) is commonly observed in cirrhotic patients and results in a reduced immune response in patients. In this respect, more careful management for OPSI should be applied in cirrhotic patients after splenectomy.

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Pathogens in OPSI: Outside the splenic circulation, polysaccharide antigens are only mildly immunogenic compared to protein antigens. This contributes to the fact that polysaccharide-coated bacteria evade the immune response and subsequent phagocytosis. Host defense against bacteria is therefore critically dependent on humoral immunity and the production of type-specific antibodies. While Kupffer cells of the liver clear the usually well-opsonized bacteria, encapsulated organisms resist antibody binding and are primarily cleared by the spleen. Sepsis in asplenic patients can occur with any organism; bacteria, viruses, fungi, or protozoa are causative. Encapsulated bacteria such as Streptococcus pneumoniae are particularly resistant to phagocytosis. Without the spleen, prompt antibody production against an emerging antigen is impaired and the bacteria multiply rapidly. Therefore, the risk of invasive pneumococcal disease is 12-25 times higher in patients without a spleen than in the general population (Aavitsland P et al (1994). The following encapsulated pathogens can preferentially cause OPSI in the asplenic patient: Streptcoccus pneumoniae (50-90%), Neisseria meningitides, Hemophilus influenzae and Streptococcus pyogenes (25%).

OPSI can occur at any age. Children are at greater risk of developing OPSI, especially children < 2 years of age (Walker W 1976). However, estimates of the incidence and timing of OPSI vary widely in the literature. Some authors report the greatest risk of developing OPSI in the first two years after splenectomy.

In the early stages of OPSI, nonspecific, mild physical symptoms of postplenectomy occur. These include fatigue, discolored skin, weight loss, abdominal pain, diarrhea, constipation, nausea, and headache (Brigden ML 1992). Pneumonia and meningitis are common, more severe associated symptoms. The clinical course can rapidly lead to coma and death within 24 to 48 h because of the high incidence of shock, hypoglycemia, marked acidosis, electrolyte abnormalities, respiratory distress, and disseminated intravascular coagulation (Chaikof EL et al 1985).

The mortality rate is 50-70% despite aggressive therapy (this includes intravenous fluids, antibiotics, vasopressors, steroids, heparin, red cell concentrates, platelets, cryoprecipitates and fresh frozen plasma) (Green JB et al 1986).

The subsequent clinical course often reflects the symptomatology of Waterhouse-Friderichsen syndrome (WFS). Bilateral adrenal hemorrhage may be found at autopsy. The mechanism linking splenectomy to Waterhouse-Friderichsen syndrome is unknown. Other possible causes of OPSI include loss of phagocytic function of the spleen, decreasing serum immunoglobulin levels, suppression of lymphocyte sensitivity, or alteration of the opsonin system (Shatz DV 2005) .

Summary clinical features of OPSI

• Cryptic infection (no obvious focus)
• Brief, nonspecific prodromal symptoms
• Massive bacteremia with encapsulated bacterial species
• Septic shock with disseminated intravascular coagulation
• Pronounced virulence: 50% to 70% mortality
• Death occurs within 24 to 48 h

Situation-adapted intensive measures.

Prevention: Prevention in immunocompromised patients who have undergone splenectomy is extremely important. Functionally or anatomically asplenic patients are at increased risk of infection by encapsulated organisms compared with the general population. Available vaccines for the most common organisms include the 23-valent pneumococcal polysaccharide vaccine, a 7-valent protein-conjugated pneumococcal vaccine, the Hemophilus influenzae type B vaccine, and the meningococcal vaccine. The polysaccharide-based pneumococcal vaccine is recommended for all adults at increased risk for pneumococcal infection, especially patients with asplenia (Musher DM et al 2005).

The Centers for Disease Control and Prevention in the United States (booster vaccination every 6 years) and the Committee for Standards in Haematology in the United Kingdom (booster vaccination every 5-10 years) recommend booster vaccination to prevent OPSI, but at the same time emphasize that shorter intervals between booster vaccinations are often necessary to maintain antibody levels at a level that is most likely to be sufficient to provide protection.

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