- Author: Neetu Radhakrishnan, MD; Chief Editor: Emmanuel C Besa, MD more...
Splenomegaly is defined as enlargement of the spleen. In the past, splenomegaly was a clinical finding, but in recent years, imaging studies have also helped to assess for or confirm mild splenomegaly.
The spleen is a functionally diverse organ with active roles in immunosurveillance and hematopoiesis. It lies within the left upper quadrant of the peritoneal cavity and abuts ribs 9-12, the stomach, the left kidney, the splenic flexure of the colon, and the tail of the pancreas. A normal spleen weighs 150 g and is approximately 11 cm in craniocaudal length.
The normal spleen is usually not palpable, although it can sometimes be palpated in adolescents and individuals with a slender build. However, an enlarged or palpable spleen is not necessarily of clinical significance. For example, certain individuals with broadly splayed costal margins have readily palpable, but small, spleens. (See Presentation.)
A spleen weight of 400-500 g indicates splenomegaly, while a weight of more than 1000 g is labelled massive splenomegaly. Poulin et al defined splenomegaly as moderate if the largest dimension is 11-20 cm, and severe if the largest dimension is greater than 20 cm.
In many instances, the spleen enlarges as it performs its normal functions. The four most important normal functions of the spleen are as follows:
Clearance of microorganisms and particulate antigens from the blood stream
Synthesis of immunoglobulin G (IgG), properdin (an essential component of the alternate pathway of complement activation), and tuftsin (an immunostimulatory tetrapeptide)
Removal of abnormal red blood cells (RBCs)
Extramedullary hematopoiesis in certain diseases
Many of the mechanisms leading to splenomegaly are exaggerated forms of normal splenic function. Although a wide variety of diseases are associated with enlargement of the spleen, the following six etiologies of splenomegaly are considered primary:
Immune response work hypertrophy - Such as in subacute bacterial endocarditis or infectious mononucleosis
RBC destruction work hypertrophy - Such as in hereditary spherocytosis or thalassemia major
Congestive - Such as in splenic vein thrombosis, portal hypertension, or Banti disease
Myeloproliferative - Such as in chronic myeloid metaplasia
Infiltrative - Such as in sarcoidosis and some neoplasms
Neoplastic - Such as in chronic lymphocytic leukemia and the lymphomas
Miscellaneous causes of splenomegaly include the following:
Giant abscess (see the images below)
Certain drugs (eg, Rho(D) immune globulin [RhoGAM])This patient has a splenic abscess due to pneumococcal bacteremia. Note that the massively enlarged spleen is readily visible, with minimal retraction in the left upper quadrant.
Acute enlargement of the spleen due to various infections or inflammatory processes results from an increase in the defense activities of the organ. The demand for increased antigen clearance from the blood may lead to increased numbers of reticuloendothelial cells in the spleen and stimulate accelerated antibody production, with resultant lymphoid hyperplasia. Examples include splenomegaly from lupus and Felty syndrome, and from viral infections such as Epstein-Barr virus–induced mononucleosis.
Removal of abnormal blood cells from the circulation (either cells with intrinsic defects or cells coated with antibody) is the usual source of hyperplastic splenomegaly. In some cases, extramedullary hematopoiesis (ie, myeloproliferative disease) results in hyperplasia.
Cirrhosis with portal hypertension, splenic vein occlusion (thrombosis), or congestive heart failure (CHF) with increased venous pressure causes congestive splenomegaly. In patients receiving oxaliplatin-based chemotherapy, splenomegaly may result from hepatic sinusoidal obstructive syndrome caused by the chemotherapy; use of bevacizumab may reduce the splenomegaly in these cases.
Infiltrative splenomegaly is the result of engorgement of macrophages with indigestible materials (eg, sarcoidosis, Gaucher disease, amyloidosis, metastatic malignancy).
Splenic filtering of blood-borne pathogens, especially encapsulated organisms, may lead to abscess formation. Because many splenic abscesses may be indolent in presentation, splenic size may increase as the abscess enlarges. This is a relatively uncommon, but important, process to recognize and treat.
Acute splenic sequestration crisis (ASSC) is a major cause of morbididty and mortality in children with sickle cell disease and other hereditary hemolytic anemias. ASSC is characterized by sudden enlargement of the spleen due to trapping of a significant proportion of the blood volume, rapid drop in the hematocrit with hypovolemia, and thrombocytopenia. ASSC is rare in adults with sickle–beta thalassemia despite the frequent presence of spleneomegaly in this population of patients. Infection and high-altitude exposure are known precipitating factors for ASSC.
In the United States, one large series reported a palpable spleen in 2% of patients and another in 5.6% of patients. Tropical splenomegaly syndrome occurs most often in persons indigenous to the malarial belt of tropical Africa and in visitors to that region.
Race-, Sex-, and Age-related demographics
No race predilection is recognized for splenomegaly. However, note that blacks may have hemoglobin SC disease, a disorder related to sickle cell disease. Unlike sickle cell disease, which results in a small, autoinfarcted spleen, patients with hemoglobin SC disease may have splenomegaly that accompanies their pigment gallstones.
Tropical splenomegaly syndrome (or hyperactive malarial syndrome) has a female-to-male incidence ratio of 2:1. Otherwise, no sex predilection is documented for splenomegaly.
The capsules of older spleens are much thinner than their younger counterparts. The combination of capsular thinning with increased spleen weight and size makes splenic injury more common in elderly persons. These factors account for the increased likelihood of splenectomy for trauma in this subgroup.
The prognosis for patients with splenomegaly is usually excellent and not substantially different from age-matched controls, but it is impacted by the underlying disease state rather than the presence of splenomegaly or the postsplenectomy state.
Morbidity and mortality
Morbidity and mortality in cases of splenomegaly principally stem from associated disease states or surgical procedures, rather than from the splenomegaly itself. The rates for morbidity and mortality are highly variable and relate to the presence or absence of comorbidities, hemorrhage, and organ failure.
Patients with enlarged spleens are more likely to have splenic rupture from blunt abdominal or low thoracic trauma. These patients are unlikely to undergo nonoperative management of their splenic injury or splenic salvage maneuvers, because their spleen is abnormal with regard to architecture, capsule tensile strength, and, commonly, hemostatic function.
Patients with splenomegaly need education with regard to decreasing their risk of splenic trauma and rupture. These patients must be cautioned about contact sports and other activities that may acutely increase intra-abdominal pressure or place excessive forces on the left upper quadrant, left flank, or lateral back. This decreases the likelihood of splenic rupture in a patient with an abnormal splenic mass and capsule. The routine use of seat belts is essential while driving or riding in a motor vehicle.
Additional education regarding the signs and symptoms of postsplenectomy sepsis cannot be overstressed. Prompt antibiotic therapy may be lifesaving.
Education represents a mandatory strategy in the prevention of overwhelming postsplenectomy infection (OPSI). Asplenic patients should be encouraged to wear a medical alert bracelet and carry a wallet card explaining their lack of a spleen. Patients should also be aware of the need to notify their physician in the event of an acute febrile illness, especially if it is associated with rigors or systemic symptoms.
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