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SplenectomyA splenectomy is the surgical procedure where the spleen is removed. The spleen plays a part in maintaining a healthy immune system and cleans the blood of foreign matter. It helps eliminate the platelets that have antibodies bound to them. Theoretically, if the spleen is removed, the platelets will stay. Splenectomies have been used to treat ITP since 1913. The published success rates vary between 50-60% although the measurement criteria for success is not standard. Splenectomized patients are at an increased risk for infections. As the time since splenectomy increases, the positive response to the procedure decreases. There is no effective method to predict a patient's response to a splenectomy. There are two types of splenectomies, laproscopic and open. The laproscopic splenectomy is becoming more popular since the healing time is reduced and it has the same rate of success as the open spelenctomy. About ten percent of the population develop an accessory (extra) spleen. Occasionally a second surgery is required if a patient develops one of these. About the Spleen ITP occurs when antibodies bind to platelets resulting in their clearance from circulation. In some instances, the antibodies may develop following an infection. Sometimes, antigen-antibody complexes adhere to platelets nonspecifically. In other cases, antiplatelet antibodies are autoantibodies. Why the antiplatelet antibodies develop is not entirely clear; however, some investigators have suggested that defects in T-cells may be involved. Alternatively, elimination of self-reactive B cells resulting in the production of autoantibodies may be involved. No matter what the mechanism, the close proximity of the B and T cells of the spleen to the circulating blood allows for exposure of platelet antigens to the immune system. This creates a continual immune response reaction resulting in the constant production of antiplatelet antibodies. These antibodies can attach to their platelet-specific antigens as the blood goes through the spleen and thus destroy the platelets. Therefore, the spleen fulfills a dual role in ITP: production of antiplatelet antibodies and removal of platelets from circulation. One of the primary functions of the spleen is filtering the blood. The filtering ability of the spleen also plays an important role in immune surveillance and response. The spleen is a meshwork of arteries, veins and reticular cells. The lymphocytes of the spleen consist of a mixture of B and T cells. The entire blood volume passes through the splenic filtration beds during the course of the day. The circulation of the spleen is unique; however, the exact details of the blood flow remain under investigation. The spleen is a secondary lymph organ and a major site of immune response to antigens. Each day the entire blood volume travels through the spleen along the intermediate/slow pathways allowing for extensive exposure of foreign and self-antigens to the immune system. The red pulp of the spleen plays an important role in removal of bacteria, foreign material, and tumor cells. The splenic B cells bind with circulating antigens. The splenic sinuses trap and destroy metastatic tumor cells. The ability of the spleen to remove bacteria is evident by the tendency of patients without spleens to be more prone to infection. A major consideration for patients with ITP is that anti-body coated platelets are removed in the red pulp of the spleen. Anti-body coated platelets may also be removed in the liver, making it difficult to predict the outcome of a splenectomy. Predicting Splenectomy Success Age as Predictor: A study reported in the British Journal of Haematology in March 2001 found "the only positive predictive factor for the long-term response to splenectomy was age <40 years." See British Journal of Haematology, March 2001, p637. Indium Screening Test as Predictor: Researchers in the UK and France feel that an indium screening test has some value in predicting whether a splenectomy will successfully raise your platelet counts. The test determines whether your spleen, liver or a combination of both is responsible for your platelet destruction. The test is performed at Barts and the Royal London Hospital in London, UK. See http://www.itppeople.com/eluise.htm for a personal account. To schedule a test in London contact Dr. Drew Provan at a.provan@virgin.net. Include your name, date of birth, address, phone number and potential test dates. To take the platelet lifespan study in Paris contact: Dr. Gil Tchernia, hôpital Bicètre-Paris, France, e-mail: gilbert.tchernia@bct.ap-hop-paris.fr To take the indium screening test in London contact Dr. Drew Provan at a.provan@virgin.net Include your name, date of birth, address, phone number and possible procedure dates. Najean, Y., Dufour, V., Rain, J.D. & Toubert, M.E. (1991) The site of platelet destruction in thrombocytopenic purpura as a predictive index of the efficacy of splenectomy. British Journal of Haematology, 79, 271-276. Najean, Y., Rain, J.-D. & Billotey, C. (1997) The site of destruction of autologous 111In-labelled platelets and the efficiency of splenectomy in children and adults with idiopathic thrombocytopenic purpura: a study of 578 patients with 268 splenectomies. British Journal of Haematology, 97, 547-550. Related Web Sites: |
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