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Splenomegaly

Diff.Dx:

1. Primary infiltration with malignant lymphoma, amyloidosis, & Gaucher's disease
2. Secondary infiltration with acute or chronic leukemia or metastatic solid tumors
3. Lymphoid hyperplasia in infectious diseases, such as bacterial endocarditis
4. Immunoregulatory disorders, such as Felty's syndrome (associated with rheumatoid arthritis and leukopenia)
5. Disorders associated with extramedullary hematopoiesis, such as myeloid metaplasia; in hemolytic states, such as thalassemia
6. Situations in which there is altered splenic blood flow, such as hepatic cirrhosis or splenic, hepatic, or portal vein thrombosis

Hypersplenism is diagnosed when there is evidence of splenic sequestration of one or more cell lines in the peripheral blood of a patient with splenomegaly and normal or hyperplastic cellularity of the bone marrow.

The diagnosis of decreased or absent splenic function is made in patients who have undergone splenectomy, had splenic irradiation, or had splenic infarction (for example, sickle cell anemia). Erythrocytes in the peripheral blood smear show dense blue inclusion granules (Howell-Jolly bodies). Patients with reduced or absent splenic function are susceptible to overwhelming infections with encapsulated organisms such as Streptococcus pneumoniae, type B Haemophilus influenzae, and Neisseria meningitidis, and should receive at least the pneumococcal vaccine.

ACP Library on Disk 2- (c) 1997 - American College of Physicians                                                             

REF: e-Medicine 2008

The causes of splenomegaly are diverse, but they may be conveniently grouped into the following categories:

1. Inflammatory splenomegaly:
   This is acute enlargement of the spleen that develops in association with various infections or inflammatory processes and results from an increase in the defense activities of the organ. The demand for increased antigen clearance from the blood may lead to increased numbers of reticuloendothelial cells in the spleen and stimulate accelerated antibody production with resultant lymphoid hyperplasia.
   
2. Infectious:
   Splenic filtering of blood-borne pathogens, especially encapsulated organisms, may lead to abscess formation. Because many splenic abscesses may be indolent in presentation, spleen size may be increased as the abscess enlarges. This is a relatively uncommon but important process to recognize and treat.
3. Infiltrative splenomegaly:
   In this setting, splenomegaly is the result of engorgement of macrophages with indigestible materials (eg, Gaucher disease, amyloidosis, metastatic malignancy).
   
4. Hyperplastic splenomegaly:
   In this setting, splenomegaly is thought to reflect work hypertrophy resulting from the removal of abnormal blood cells from the circulation (either cells with intrinsic defects or cells coated with antibody) or, in some cases, as the result of extramedullary hematopoiesis (ie, myeloproliferative disease).
5. Congestive splenomegaly:
   This condition develops as a result of cirrhosis with portal hypertension, splenic vein occlusion (thrombosis), or congestive heart failure (CHF) with increased venous pressure.