SPLENOMEGALY SPLENUNCULI SCANNING

Splenomegaly
Enlargement of the spleen is a highly non-specific sign associated with numerous conditions, the most common being infection, portal hypertension, haematological disorders and neoplastic conditions. As with the liver, measurement of splenic volume is usually considered inaccurate due to variations in shape, and not reproducible. However, the length of the spleen is an adequate indicator of size for most purposes and provides a useful baseline for monitoring changes in disease status. The length of the normal adult spleen is less than 12 cm.

The spleen enlarges downwards and medially. Its inferior margin becomes rounded, rather than pointed, and may extend below the left kidney. Although the aetiology of splenomegaly may not be obvious on ultrasound, the causes can be narrowed down by considering the clinical picture and by identifying other relevant appearances in the abdomen. Splenomegaly due to portal hypertension, for example, is frequently accompanied by other associated pathology such as cirrhotic liver changes, varices or ascites.

Examples of causes of splenomegaly
● Portal hypertension
● Acute or chronic systemic infection, e.g. hepatitis, AIDS, infectious mononucleosis, sepsis
● Haemolytic anaemia, sickle cell disease, thalassaemia, pernicious anaemia, spherocytosis
● Malignancy—leukaemia, Hodgkin’s and non-Hodgkin’s lymphoma, myeloproliferative disorders
● Storage disorders
● Immunological diseases

Splenunculi
In around 10% of the population, a small accessory spleen, or splenunculus, may be located at the splenic hilum. These small, well-defined ectopic nodules of splenic tissue rarely exceed 2 cm in diameter. Splenunculi enlarge under the same circumstances as those which cause splenomegaly and may also hypertrophy in postsplenectomy patients. The importance of recognizing these lies in differentiating them from lymph nodes, left adrenal nodules or masses in the tail of pancreas. Colour Doppler may identify the vascular supply as being common to the main spleen.

Pitfalls in scanning the spleen
● In hepatomegaly, the left lobe of liver may extend across the abdomen, indenting the spleen. This can give the appearance of a homogeneous, intrasplenic ‘mass’ when the spleen is viewed coronally. A transverse scan at the epigastrium should demonstrate the extent of left hepatic enlargement and confirm its relationship to the spleen.
● Splenunculi may be mistaken for enlarged lymph nodes at the splenic hilum. Colour Doppler can confirm the vascular supply is shared by the spleen.
● The normal tail of pancreas may mimic a perisplenic mass.
● A left adrenal mass, or upper pole renal mass, may indent the spleen making it difficult to establish the origin of the mass.