SPLENOMEGALY

Most occurrences of splenomegaly result from one of seven basic mechanisms.

• One of the most common of these mechanisms is hyperplasia of cells of the RES system or lymphoid lines. This occurs in many acute systemic infections, in autoimmune disease, viz. Felty's Syndrome and SLE, and in thyrotoxicosis. Common infectious causes of splenomegaly include infectious endocarditis, tuberculosis, infectious mononucleosis, and histoplasmosis.
• Passive congestive splenomegaly: most often this results from hepatic disease, especially cirrhosis (Banti's Syndrome), with portal hypertension. However, thrombosis of the splenic or portal veins and cor pulmonale can have the same effect. Reactive hyperplasia of the RES cells of the red pulp often occurs in congestive splenomegaly, adding further to the size of the spleen. Splenomegaly due to this mechanism is usually asymptomatic.
• Abnormal RBC morphology (especially hereditary spherocytosis, thalassemias, and early SSA), autoimmune hemolytic anemia, and polycythemia vera can cause trapping of erythrocytes in red pulp sinusoids. This produces congestive splenomegaly, and anemia as well. The finding of anemia alone does not make this diagnosis, however, since splenomegaly from most other causes is accompanied by increased splenic sequestration of RBCs (as well as other formed blood elements); further analysis is required.
• Splenic hematopoiesis occurs in states of bone marrow insufficiency, most commonly resulting from myeloid metaplasia and the myelophthisic syndromes. In such situations, anemia is generally found in addition to splenomegaly.
• Malignancies, either metastatic or primary to the spleen, constitute another major mechanism of splenomegaly. The most common primary splenic cancers are lymphomas (Hodgkin's and non-Hodgkin's), chronic lymphocytic and granulocytic leukemias, and the acute leukemias. Splenomegaly accompanied by generalized lymphadenopathy suggests lymphoma or CLL.
• Infiltration of the spleen with abnormal material occurs in a number of diseases, including amyloidosis and various "storage diseases" (e.g. Gaucher's, Neimann-Pick's). Splenomegaly from this causes is often complicated by reactive hyperplasia of red-pulp macrophages.
• Various non-neoplastic space-occupying lesions: Hemangiomas, cysts, and hematomas are the most common entities in this category. Others include infectious granulomas (in mycobacterial and fungal disease), non-infectious granulomas (e.g. in sarcoidosis), and infarcts. Ischemic infarcts occur often in SSA, resulting from blockage of splenic sinusoids with deformed RBCs. They also result from cardioemboli, usually from valvular vegetations in SBE or from mural thrombi. 99Tc-radionuclide scanning of the spleen is useful in identifying areas of infarct.

Clinical evaluation:

• In the setting of acute illness, splenomegaly is likely to be due to reactive hyperplasia or space-occupying lesions. The spleen tends to be soft on palpation, with blunt edges
• In chronic illness, the mechanisms of congestion, splenic hematopoiesis, malignancy, or infiltrative processes are more probabl. S hard, sharp-edged spleen is often felt.
• Presentation of splenomegaly with left-upper quadrant pain and splenic tenderness suggests infarction, subcapsular hematoma, or rupture due to trauma or infection (infectious mononucleosis, typhoid fever, and malaria are known to cause splenic rupture).
• Asymptomatic splenomegaly is commonly due to passive congestion.
• Fever accompanying splenomegaly points to an infectious etiology; fever, rash, and arthralgias, however, suggest autoimmune disease.

Diagnosis:

• 99Tc-radionuclide scan--most useful in identifying infarcts
• Ultrasonography
• CT scanning.
• Bone marrow aspiration can identify many of the causes of splenomegaly, including leukemia, lymphoma, lipid storage diseases, amyloidosis, disseminated fungal or mycobacterial disease, and metastatic cancer.
• In some cases, diagnostic splenectomy is the only way to identify the cause of splenomegaly.

Adams' classification of the causes of splenomegaly by the degree of splenic enlargement is considered to be a useful tool in narrowing the enormous differential in hard-to-diagnose cases. This classification is noteworthy in that causes of splenomegaly which share the same mechanism (e.g. CHF, hepatic cirrhosis, and HPV obstruction) do not fall into the same category of degree of splenic enlargement.

• Slight enlargement:

• Chronic passive congestion secondary to CHF
• Acute malaria
• Typhoid fever
• SBE
• SLE, RA
• Thalassemia minor

• Moderate enlargement:

• Hepatitis
• Hepatic cirrhosis
• Lymphoma, leukemia
• Rickets
• Infectious mononucleosis
• Hemolytic anemia
• Splenic abcess/infarct
• Amyloidosis

• Severe enlargement:

• CML
• Myelophthisis
• Gaucher's, Neimann-Pick's
• Hepatic portal vein obstruction
• Thalassemia major
• Sarcoidosis
• Chronic malaria