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Everything you need to know about Computed Tomography (CT) & CT Scanning


MDCT of the Spleen: Splenomegaly

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Normal spleen size varies with patient age, size and underlying metabolic conditions. On average, the spleen measure 12 x 7 x 4 cm with a weight of 150 grams. Occasionally splenic index is used to estimate normal spleen size by multiplying the 3 dimensions. (Normal range 120-480 cm3). However, most radiologists eyeball the size of the spleen and approximate if it is with in normal limits. For example, the inferior tip of the spleen should not extend below the inferior tip of the right hepatic lobe. Also, the AP diameter of the spleen should be less than 2/3 of the abdominal diameter.

CT is useful for determining the degree of splenomegaly and whether the underlying cause is due to a focal or diffuse abnormality. CT also allows visualization of other abnormalities linking to primary to secondary disease and allowing a more precise diagnosis. For instance, patients with lymphoma usually have adenopathy in addition to focal splenic lesion. The source for splenic abscess may be found in other parts of the exam such as adjacent pancreatitis or endocarditis. And individuals with sickle cell disease may have an atrophic, calcified spleen in addition to classic osseous abnormalities.

A wide variety of conditions may produce splenomegaly. Alteration of blood flow patterns through the portal venous system is one of the most common causes of splenomegaly. Splenic enlargement occurs in patients with cirrhosis who develop portal hypertension. The spleen also increases in individuals with portal vein thrombosis altering flow patterns. Ancillary CT findings may consist of characteristic nodular hepatic appearance as with cirrhosis or development of venous collaterals indicating portal hypertension or portal vein occlusion. Isolated splenic vein thrombosis can also produce splenomegaly. This commonly occurs in patients with pancreatitis or pancreatic cancer inducing obstruction. Patient with congestive heart failure may also present with an enlarged spleen.

Infiltrating disease such as lymphoma and leukemia may result in diffuse splenic enlargement, and observers should search for additional abdominal adenopathy. Metabolic conditions including sarcoidosis and Gaucher's disease often produce splenomegaly due to infiltration. In sarcoidosis non-caseating granulomas infiltrate the spleen while in Gaucher's disease there is accumulation of ceramide.

A variety of infectious processes such as mononucleosis and granulomatous disease may cause splenomegaly. Further causes include hemolytic anemias, extramedullary hematopoeisis as with myelofibrosis, and collagen vascular diseases including systemic lupus erythematosis and rheumatoid arthritis.

The differential diagnosis for splenomegaly is extremely broad and imaging characteristics nonspecific. Therefore, clinical correlation is critical to determine underlying etiology of splenomegaly.

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