Enlarged Spleen: Causes, Symptoms, and Treatments

Common Lesions Of The Spleen

Spleen Normal Structure:

The spleen is the largest lymphoid organ of the body. Under normal conditions, the average weight of the spleen is about 150 gm in the adult. Normally, the organ lies well protected by the 9th, 10th and 11th ribs in the upper left quadrant.

The surface of the spleen is covered by a layer of peritoneum underneath which the organ is ensheathed by a thin capsule. From the capsule extend connective tissue trabeculae into the pulp of the organ and serve as supportive network.

Blood enters the spleen by the splenic artery which divides into branches that penetrate the spleen via trabeculae. From the trabeculae arise small branches called central arterioles.

Blood in the central arterioles empties partly into splenic venules and from there into splenic vein, but largely into vascular sinuses of the red pulp and thence into the splenic venous system.

Read And Learn More: General Pathology Notes

Grossly, the spleen consists of homogeneous, soft, dark red mass called the red pulp and long oval grey-white nodules called the white pulp (malpighian bodies).

Microscopically, the red pulp consists of a network of thin-walled venous sinuses and adjacent blood spaces. The blood spaces contain blood cells, lymphocytes and macrophages and appear to be arranged in cords called splenic cords or cords of Billroth. The white pulp is made up of lymphocytes surrounding an eccentrically placed arteriole.

The periarteriolar lymphocytes are mainly T-cells, while at other places the lymphocytes have a germinal centre composed principally of B-cells surrounded by densely packed lymphocytes.

The spleen is a lymphoreticular organ that performs at least the following four functions:

1. Like other lymphoid tissues, it is an organ of the immune system where B and T lymphocytes multiply and help in immune responses.
2. The spleen plays an active role in sequestering and removing normal and abnormal blood cells.
3. The vasculature of the spleen plays a role in regulating portal blood flow.
4. Under pathologic conditions, the spleen may become the site of extramedullary haematopoiesis.

The spleen is rarely the primary site of disease. Being the largest lymphoreticular organ, it is involved secondarily in a wide variety of systemic disorders which manifest most commonly as splenic enlargement (splenomegaly) described below.

A few other systemic involvements such as amyloidosis, splenic infarcts, chronic venous congestion (CVC) of the spleen, storage diseases etc have already been considered in General Pathology.

Splenic Enlargement:

Splenomegaly:

Enlargement of the spleen termed splenomegaly, occurs in a wide variety of disorders which increase the cellularity and vascularity of the organ. Many of the causes are exaggerated forms of normal splenic function.

Massive Splenomegaly

Splenic enlargement may occur as a result of one of the following pathophysiologic mechanisms:

1. Infections
2. Disordered immunoregulation
3. Altered splenic blood flow
4. Lymphohaematogenous malignancies
5. Diseases with abnormal erythrocytes
6. Storage diseases
7. Miscellaneous causes.

Based on these mechanisms, an abbreviated list of causes of splenomegaly is given in Table. Most of these conditions have been discussed elsewhere.

The degree of splenomegaly varies with the disease entity:

• Mild enlargement (up to 5 cm) occurs in CVC of spleen in CHF, acute malaria, typhoid fever, bacterial endocarditis, SLE, rheumatoid arthritis and thalassaemia minor.
• Moderate enlargement (up to umbilicus) occurs in hepatitis, cirrhosis, lymphomas, infectious mononucleosis, haemolytic anaemia, splenic abscesses and amyloidosis.
• Massive enlargement (below umbilicus) occurs in CML, myeloid metaplasia with myelofibrosis, storage diseases, thalassaemia major, chronic malaria, leishmaniasis and portal vein obstruction.

Mild to moderate splenomegaly is usually symptomless, while a massively enlarged spleen may cause dragging sensation in the left hypochondrium. Spleen becomes palpable only when it is enlarged.

Grossly, an enlarged spleen is heavy and firm. The capsule is tense and thickened. The sectioned surface of the organ is firm with prominent trabeculae

Splenomegaly Causes

Microscopically, there is dilatation of sinusoids with prominence of splenic cords. The white pulp is atrophic while the trabeculae are thickened. Long-standing congestion may produce haemorrhages and Gamna-Gandy bodies resulting in fibrocongestive splenomegaly, also called Banti’s spleen.

Hypersplenism:

The term hypersplenism is used for conditions which cause excessive removal of erythrocytes, granulocytes or platelets from the circulation. The mechanism for excessive removal could be due to increased sequestration of cells in the spleen by altered splenic blood flow or by production of antibodies against respective blood cells.

The criteria for hypersplenism are as under:

1. Splenomegaly.
2. Splenic destruction of one or more of the cell types in the peripheral blood causing anaemia, leucopenia, thrombocytopenia, or pancytopenia.
3. Bone marrow cellularity is normal or hyperplastic.
4. Splenectomy is followed by improvement in the severity of blood cytopenia.

Splenectomy And Splenic Rupture:

Effects Of Splenectomy:

In view of the prominent role of normal spleen in sequestration of blood cells, splenectomy in a normal individual is followed by significant haematologic alterations. Induction of similar haematologic effects is made use in the treatment of certain pathologic conditions.

Splenomegaly Causes

For example, in autoimmune haemolytic anaemia or thrombocytopenia, the respective blood cell counts are increased following splenectomy.

The blood changes following splenectomy are as under:

1. Red cells: There is appearance of target cells in the blood film. Howell-Jolly bodies are present in the red cells as they are no longer cleared by the spleen. Osmotic fragility test shows increased resistance to haemolysis. There may be appearance of normoblasts.

2. White cells: There is leucocytosis reaching its peak in 1-2 days after splenectomy. There is shift-to-left of the myeloid cells with appearance of some myelocytes.

3. Platelets: Within hours after splenectomy, there is rise in platelet count upto 3-4 times normal.

Splenic Rupture:

The most common cause of splenic rupture or laceration is blunt trauma. The trauma may be direct or indirect. Non-traumatic or spontaneous rupture occurs in an enlarged spleen but almost never in a normal spleen.

In acute infections, the spleen can enlarge rapidly to 2 to 3 times its normal size causing acute splenic enlargement termed acute splenic tumour e.g. in pneumonias, septicaemia, acute endocarditis etc.

Some of the other common causes of spontaneous splenic rupture are splenomegaly due to chronic malaria, infectious mononucleosis, typhoid fever, splenic abscess, thalassaemia and leukaemias.

Rupture of spleen is an acute surgical emergency due to rapid blood loss and haemoperitoneum. Sometimes fragments of splenic tissue are autotransplanted within the peritoneal cavity and grow into tiny spleens there (splenosis).

Splenic Tumours:

Primary tumours of the spleen are extremely rare.

• The only notable benign tumours are haemangiomas and lymphangioma.
• Primary malignant neoplasms of haematolymphoid system (i.e. Hodgkin’s disease, nonHodgkin’s lymphomas and leukaemias) may involve the spleen sometimes.
• Common non-haematopoietic tumour of the spleen is angiosarcoma which is rare.

Splenomegaly Treatment

Secondary tumours occur late in the course of disease and represent haematogenous dissemination of the malignant tumour. Splenic metastases appear as multiple nodules. The most frequent primary sites include cancers of lung, breast, prostate, colon, stomach and ovary. Rarely, direct extension from an adjacent malignant neoplasm may occur.

Common Lesions of the Spleen:

• Enlargement of the spleen, splenomegaly, may result from a variety of causes and may produce mild, moderate and marked enlargement. Underlying causes of enlargement may be infectious, disordered immunoregulation, altered splenic blood flow, haematolymphoid malignancies, diseases of erythroid series, storage diseases etc.
• Hypersplenism is a condition which causes excessive removal of red cells, granulocytes and platelets; thus there is pancytopenia.
• Removal of spleen may cause appearance of target cells, leucocytosis, and thrombocytosis.
• Splenic rupture may occur from blunt trauma, especially if it is enlarged.
• Spleen may be the site of primary (e.g. haemangioma, lymphoma) and metastatic tumours (cancer of lung, breast, prostate ovary etc