Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + THE SPLEEN Download Section PDF Listen +++ ++ The white pulp (lymphoid tissue) functions in antigen processing and antibody production. The red pulp (monocyte-macrophage system) serves as a filter, retaining defective blood cells and foreign particles. + HYPERSPLENISM (INCREASED SPLENIC FUNCTION) Download Section PDF Listen +++ ++ Hypersplenism is considered “appropriate” if it is an exaggeration of normal function, as in hereditary spherocytosis or idiopathic thrombocytopenic purpura, or “inappropriate” if the hyperfunction is a result of vascular congestion or infiltrative disease. It is usually associated with splenomegaly. It causes cytopenias with associated compensatory bone marrow hyperplasia. It usually is corrected by splenectomy, if indicated. Table 26–1 lists the causes of hypersplenism. Table 26–2 lists the causes of massive splenomegaly. ++Table Graphic Jump LocationTABLE 26–1CLASSIFICATION AND THE MOST COMMON CAUSES OF SPLENOMEGALY AND HYPERSPLENISMView Table||Download (.pdf) TABLE 26–1 CLASSIFICATION AND THE MOST COMMON CAUSES OF SPLENOMEGALY AND HYPERSPLENISM Congestive Right-sided congestive heart failure Budd-Chiari syndrome (hepatic vein thrombosis with or without inferior vena cava extension) Cirrhosis with portal hypertension Portal or splenic vein thrombosis Immunologic Viral infection Acute HIV infection/chronic infection Acute mononucleosis Dengue fever Rubella (rare except newborns) Cytomegalovirus infection (rare except newborns) Herpes simplex (rare except newborns) Bacterial infection Subacute bacterial endocarditis Brucellosis Tularemia Melioidosis Listeriosis Plague Secondary syphilis Relapsing fever Psittacosis Anaplasmosis (formerly ehrlichiosis) Rickettsial diseases (scrub typhus, Rocky Mountain spotted fever, Q fever) Tuberculosis Splenic abscess (most common organisms are Enterobacteriaceae, Staphylococcus aureus, streptococcus group D, and anaerobic organisms as part of mixed flora infections) Fungal Infection Blastomycosis Histoplasmosis Systemic candidiasis and hepatosplenic candidiasis Parasitic infection Malaria Kala-azar Leishmaniasis Schistosomiasis Babesiosis Coccidioidomycosis Paracoccidioidomycosis Trypanosomiasis (cruzi, brucei) Toxoplasmosis (rare except newborns) Echinococcosis Cysticercosis Visceral larva migrans (Toxocara infection) Inflammatory/autoimmune Systemic lupus erythematosus (SLE) Felty syndrome Juvenile rheumatoid arthritis Autoimmune lymphoproliferative syndrome (ALP syndrome) Hemophagocytic syndrome Common variable immunodeficiency Anti-D immunoglobulin administration Associated with hemolysis Thalassemia major and intermedia Pyruvate kinase deficiency Hereditary spherocytosis Autoimmune hemolytic anemia (rare) Sickle cell disease, more common in early childhood (splenic sequestration), hemoglobin C disease, and some other hemoglobinopathies Infiltrative Nonmalignant Splenic hematoma (splenic cysts are usually a late complication of a hematoma) Littoral cell angioma Disorders of sphingolipid metabolism Gaucher disease Niemann-Pick disease Cystinosis Amyloidosis (light-chain amyloid and amyloid A protein) Multicentric Castleman disease Mastocytosis Hypereosinophilic syndrome Sarcoidosis Extramedullary hematopoiesis Primary myelofibrosis Osteopetrosis (childhood) Thalassemia major Malignant Hematologic Chronic lymphocytic leukemia (especially prolymphocytic variant) Chronic myeloid leukemia Polycythemia vera Hairy cell leukemia Heavy chain disease Hepatosplenic lymphoma Acute leukemia (acute lymphoblastic leukemia/acute myeloid leukemia) Hodgkin and other lymphomas Nonhematologic Metastatic carcinoma (rare) Neuroblastoma Wilms tumor Leiomyosarcoma Fibrosarcoma Malignant fibrous histiocytoma Kaposi sarcoma Hemangiosarcoma Lymphangiosarcoma Hemangioendothelial sarcoma Iatrogenic Granulocyte colony-stimulating factor administration Erythropoietin administration Source: Williams Hematology, 9th ed, Chap. 56, Table 56–1. ++Table Graphic Jump LocationTABLE 26–2CAUSES OF MASSIVE SPLENOMEGALYView Table||Download (.pdf) TABLE 26–2 CAUSES OF MASSIVE SPLENOMEGALY Myeloproliferative disorders Primary myelofibrosis Chronic myeloid leukemia Lymphomas Hairy cell leukemia Chronic lymphocytic leukemia (especially prolymphocytic variant) Infectious Malaria Leishmaniasis (kala azar) Extramedullary hematopoiesis Thalassemia major Infiltrative: Gaucher disease Source: Williams Hematology, 9th ed, Chap. 56, Table 56–2. +++ Pathophysiology ++ The normal spleen carries out filtration and elimination of aged and defective blood cells. This same process also removes red cells with hereditary abnormalities of red blood cell membrane and antibody-coated blood cells. An enlarged spleen may sequester and destroy normal blood cells, leading to symptomatic cytopenias. An expanded splenic (systemic) plasma pool may cause further anemia by dilution. Massively increased splenic blood flow, especially if there is decreased hepatic compliance, may cause portal hypertension, further splenomegaly, and associated gastroesophageal varices. Massive splenomegaly will cause early satiety, mediated by mechanical effects on the stomach. +++ Effect on Platelets ++ Normally, about one third of the platelet mass is sequestered in the spleen. Up to 90% of platelets may be sequestered temporarily by a very enlarged spleen. Platelets survive almost normally in the spleen and are available, albeit slowly, when needed. +++ Effect on Neutrophils ++ A large fraction of the circulating neutrophil pool may be marginated in an enlarged spleen. Neutrophils survive almost normally in the spleen and, like platelets, slowly become available on demand. +++ Effect on Red Blood Cells ++ Red blood cells are metabolically more vulnerable than leukocytes or platelets and may be destroyed prematurely in red pulp. Spherocytes may be formed during repeated or prolonged metabolic conditioning in the red pulp. +++ Symptoms of Splenomegaly ++ Splenomegaly may be asymptomatic. Very rapid enlargement of the spleen may cause some pain due to strain on the splenic capsule. Greatly enlarged spleens may cause abdominal discomfort, trouble sleeping on the left side, and early satiety. Splenic infarction may cause pleuritic-like left upper quadrant or shoulder pain, with or without a friction rub. In young patients with sickle cell anemia, the spleen may become acutely enlarged and painful due to obstruction of the splenic outflow, with sudden aggravation of anemia (sequestration crisis). +++ Estimation of Splenic Size ++ A spleen of normal size may be palpable in young and thin patients with low diaphragms. Otherwise, a palpable spleen should be considered to be enlarged. Splenic size can be assessed with abdominal ultrasound (Figure 26–1), computed tomography (CT) (Figure 26–2), or magnetic resonance imaging (MRI) examination. Cysts, tumors, or infarcts of the spleen may be identified by radionuclide colloid scanning, abdominal CT, or MRI. ++ FIGURE 26–1 A three-way composite of abdominal computed tomography. A. Normal spleen size. B. Enlarged spleen. C. Massively enlarged spleen at the level of mid-kidney. Normally the spleen would either not be visualized or only a small lower pole would be evident at the latter level. (White arrows mark the edge of the splenic silhouette.) (Used with permission from Deborah Rubens, MD, The University of Rochester Medical Center.) Graphic Jump LocationView Full Size||Download Slide (.ppt) ++ FIGURE 26–2 A two-way composite of ultrasonographic examination for spleen size. Patient’s head is to the left side of the longitudinal image. A. Image of echo indicating normal spleen size with cranial to caudal longitudinal dimension of 10.3 cm. B. Image of echo indicating enlarged spleen with cranial to caudal longitudinal dimension of 16.2 cm. (White arrows mark the edge of the splenic silhouette.) The normal spleen is usually less than 13 cm in length, but the examiner has to consider other dimensions in assessing spleen size (volume). (Used with permission from Deborah Rubens, MD, The University of Rochester Medical Center.) Graphic Jump LocationView Full Size||Download Slide (.ppt) +++ Hematologic Features of Splenomegaly ++ The blood concentration of erythrocytes, leukocytes, or platelets is reduced in the blood, with corresponding hyperplasia in the marrow. Cellular morphology is usually normal. +++ Splenectomy ++ This procedure may be required for severe, dangerous cytopenias and can lead to dramatic improvement of blood counts, sometimes to normal, in patients with hypersplenism. It may alleviate portal hypertension but is not the preferred primary treatment. It will alleviate painful splenic infarcts. After splenectomy, there may be a rapid, but temporary, increase in the platelet count, which can lead to thromboembolic complications, especially in the elderly or in bedridden patients. Chronic changes in the blood after splenectomy are listed below in “Hyposplenism, Laboratory Findings.” Splenectomy removes a protective filter bed and renders the patient vulnerable to bacteremia, especially due to encapsulated gram-positive organisms. Therefore, vaccination against such organisms (eg, Streptococcus pneumoniae, Haemophilus influenzae) should precede elective splenectomy by 2 to 3 weeks if at all possible. The procedure diminishes resistance to preexisting parasitic disease (malaria, bartonellosis, babesiosis) and transforms dormant infestation into active disease. Partial splenectomy has been used in special circumstances to decrease hypersplenism and prevent hyposplenism. The frequency of splenectomy for some disorders has decreased in recent years because of improved alternative therapies or a higher threshold for recommending the procedure. Splenectomy is still recommended under specific conditions for some disorders, as discussed in specific chapters (eg, Chap. 13, Erythrocyte Membrane Disorders; Chap. 22, Hemolytic Anemia Resulting from Warm-Reacting Antibodies; Chap. 47, Primary Myelofibrosis, and Chap. 73, Thrombocytopenia). However, as a result of higher risks of overwhelming infection, splenectomy should be postponed, if at all possible, until after age 5. + HYPOSPLENISM (DECREASED SPLENIC FUNCTION) Download Section PDF Listen +++ ++ Splenic function may be reduced by disease or surgical removal. Hyposplenism may or may not be associated with reduced splenic size. Impaired filtering causes mild thrombocytosis and increased risk of severe bloodstream infections. 99mTc sulfur colloid uptake is a reliable measure of the capacity of the spleen to clear particulates from the blood. Causes of hyposplenism are listed in Table 26–3. ++Table Graphic Jump LocationTABLE 26–3CONDITIONS ASSOCIATED WITH HYPOSPLENISMView Table||Download (.pdf) TABLE 26–3 CONDITIONS ASSOCIATED WITH HYPOSPLENISM Miscellaneous Surgical splenectomy Splenic irradiation Sickle hemoglobinopathies Congenital asplenia Thrombosis of splenic artery or vein Normal infants Gastrointestinal and hepatic diseases Celiac disease Dermatitis herpetiformis Inflammatory bowel disease Cirrhosis Autoimmune disorders Systemic lupus erythematosus Rheumatoid arthritis Vasculitis Glomerulonephritis Hashimoto thyroiditis Sarcoidosis Hematologic and neoplastic disorders Graft-versus-host disease Chronic lymphocytic leukemia Non-Hodgkin lymphoma Hodgkin lymphoma Amyloidosis Advanced breast cancer Hemangiosarcoma Sepsis/infectious diseases Malaria Disseminated meningococcemia Source: Williams Hematology, 9th ed, Chap. 56, Table 56–3. +++ Infectious Complications ++ Overwhelming sepsis is often fatal. The condition is usually caused by encapsulated bacteria, such as pneumococcus or H. influenzae. Risk greatest in very young and splenectomy usually contraindicated before age 4 years. Healthy adults with splenectomy because of accidental rupture of normal spleen are still at some increased risk. +++ Laboratory Findings ++ Slight to moderate increase in leukocyte and platelet counts Target cells, acanthocytes, and other misshapen erythrocytes Howell-Jolly bodies (nuclear fragment remnants) in one red cell per 100 to 1000 Pitted erythrocytes (wet preparation, using direct interference-contrast microscopy) Increased numbers of Heinz bodies on supravital examination Increased numbers of nucleated red cells in patients splenectomized for various hemolytic disorders +++ Treatment of Hyposplenic or Postsplenectomy Patient ++ Immunize with polyvalent pneumococcal vaccine before splenectomy. Vaccinate children against H. influenzae. Prophylactic penicillin is usually given to asplenic children. All febrile infections should be considered serious. Administer an appropriate antibiotic regimen immediately on onset of symptoms. Treat with broad-spectrum antibiotics at the time of all dental work (especially extractions). ++ For a more detailed discussion, see Jaime Caro and Srikanth Nagalla: Hypersplenism and Hyposplenism, Chap. 56 in Williams Hematology, 9th ed.
For a more detailed discussion, see Jaime Caro and Srikanth Nagalla: Hypersplenism and Hyposplenism, Chap. 56 in Williams Hematology, 9th ed.