The term splenomegaly generally denotes a palpably enlarged spleen. However, it may also refer to an enlarged spleen detected by an imaging test. Splenomegaly can be found in 3% of the normal population. 
It is difficult to create a stepwise algorithmic approach to the patient with splenomegaly.  Categorisation by presentations such as massive splenomegaly, isolated splenomegaly, or accompanying symptoms could be considered. However, these categories encompass diverse diagnoses. For example, thalassaemia, chronic myeloid leukaemia, Gaucher's disease, hairy cell leukaemia, myelofibrosis, and malaria may all present with a markedly enlarged spleen. Isolated splenomegaly is a feature of diagnoses such as splenic marginal lymphoma or benign splenic neoplasms. Accompanying symptoms such as fever are features of lymphomas, malaria, endocarditis, or infectious mononucleosis.
An average human spleen is 10 cm long and weighs 150 grams.  Abnormal enlargement of the spleen, splenomegaly, is usually determined by physical examination. It may be difficult to palpate an enlarged spleen in the settings of obesity, a muscular abdominal wall, or the inability to sufficiently relax the abdominal musculature. In these cases, spleen size may need to be determined by radiographical tests. It is not uncommon for a radiologist interpreting a chest x-ray to comment that the spleen seems enlarged (usually considered an incidental finding). If splenomegaly is suspected, an ultrasound of the left upper quadrant can be helpful, with the advantage of lack of exposure to radiation. Computed tomography and nuclear imaging (liver-spleen scan) may be complementary; the former may confirm an enlarged spleen, whereas a liver-spleen scan may contribute valuable information about the presence of colloid shift, signifying portal hypertension.
In selected patients, especially those with portal vein or splenic vein thrombosis, Doppler venous ultrasonography or magnetic resonance imaging studies may be necessary to determine whether veins draining the spleen are affected by clots (portal vein thrombosis, splenic vein thrombosis).
Fine-needle aspiration of splenic lesions can be accomplished in selected cases but may expose the patient to risk of splenic rupture. It should be performed only by an experienced interventional radiologist with surgical support in case of splenic laceration or rupture. Ultimately, some splenic lesions can be diagnosed only by splenectomy with pathological examination of the removed organ.
Assistant Professor of Medicine
Section of Hematology
Yale School of Medicine
Smilow Cancer Center at Yale-New Haven
TLP declares that she has no competing interests.
Dr Terri L. Parker would like to gratefully acknowledge Dr Alan E. Lichtin, the previous contributor to this monograph.
Bristol Haematology and Oncology Centre
PM declares that she has no competing interests.
Professor of Medicine
RAM declares that he has no competing interests.
Director of the Laboratory of Clinical Epidemiology
IRCCS Policlinico S. Matteo Foundation
GB declares that he has no competing interests.
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