Splenomegaly
Splenomegaly is an enlargement of the spleen beyond its normal size. It is a sign rather than a diagnosis in its own right and can result from many different conditions, including infections, chronic liver disease and portal hypertension, blood disorders, lymphoma and other cancers, congestion from heart disease, autoimmune diseases, infiltrative or storage disorders, and a variety of less common causes. The clinical significance of splenomegaly depends entirely on the underlying cause. Imaging—particularly ultrasound, CT, and MRI—plays a central role in measuring spleen size and identifying contributing conditions.
What is it?
The spleen is an organ in the upper left abdomen, tucked beneath the diaphragm and behind the stomach. It plays important roles in filtering aging or abnormal blood cells, supporting immune function, helping fight certain infections, and—in some conditions—producing blood cells. Splenomegaly is an enlargement of the spleen beyond what is expected for the patient’s body habitus, age, and sex. Different definitions are used: a spleen length greater than approximately 12 to 13 centimeters in adults on imaging is commonly considered enlarged, although clinical judgment is important. “Massive splenomegaly” refers to very large spleens, often extending well below the rib cage and across the abdomen, and tends to suggest specific underlying conditions.
Many different conditions can lead to splenomegaly, and the spleen can enlarge for several distinct reasons. The most common categories include congestive splenomegaly (related to increased blood flow or pressure, particularly from chronic liver disease and portal hypertension, heart failure, or splenic vein thrombosis), infectious splenomegaly (from acute viral infections such as mononucleosis, chronic viral infections, bacterial infections such as endocarditis or tuberculosis, parasitic infections such as malaria, leishmaniasis, or schistosomiasis, and others), hematologic conditions (including hemolytic anemias, hereditary spherocytosis, sickle cell disease in childhood, thalassemias, and myeloproliferative neoplasms), lymphoid cancers and other malignancies (such as lymphoma, leukemia, and—less commonly—primary splenic tumors or metastases), autoimmune and inflammatory conditions (such as lupus, rheumatoid arthritis with Felty syndrome, sarcoidosis, and IgG4-related disease), infiltrative and storage disorders (including Gaucher disease, amyloidosis, and other rare conditions), and miscellaneous causes (such as splenic cysts, hematomas, vascular abnormalities, and idiopathic enlargement).
The combination of splenomegaly with low blood counts is called hypersplenism. In hypersplenism, the enlarged spleen overactively removes blood cells from circulation, producing varying degrees of anemia, low white blood cell counts (leukopenia), and low platelet counts (thrombocytopenia). The presence of cytopenias often influences the urgency of evaluation and management.
Symptoms vary widely depending on the underlying cause, the size of the spleen, and the rate at which it has enlarged. Many patients with mild splenomegaly have no symptoms, and the finding is identified incidentally on examination or imaging done for other reasons. As enlargement progresses, common features include vague upper left abdominal pain or fullness, early fullness with meals (when the enlarged spleen presses on the stomach), discomfort that may radiate to the left shoulder, and—in some patients—a palpable mass below the left rib cage. Symptoms specific to the underlying cause—such as fever, night sweats, weight loss, jaundice, fatigue, frequent infections, easy bruising or bleeding, joint pain, or rash—often provide important clues. Sudden severe pain or signs of significant blood loss can suggest splenic rupture, which is a medical emergency.
Evaluation begins with a careful history and physical examination, including assessment of risk factors for infection, travel history, exposures, family history, and any signs or symptoms of the conditions listed above. Basic blood tests include a complete blood count, peripheral blood smear (which can identify many specific conditions), comprehensive liver function tests, kidney function, inflammatory markers, and—based on the clinical picture—viral hepatitis testing, HIV testing, infectious disease studies, autoimmune markers, hemolysis studies, immunoglobulin levels, and specialized hematologic tests. Ultrasound of the abdomen is often the first imaging study and provides reliable measurement of spleen size, evaluation of the liver, assessment of portal blood flow, and identification of focal lesions. CT and MRI provide more detailed information about splenic architecture, focal lesions, lymph nodes, and the rest of the abdomen, and are particularly useful when malignancy or specific structural disease is suspected. Bone marrow biopsy may be considered in selected cases, particularly when hematologic disease is suspected. Other specialized tests are individualized based on the suspected underlying condition.
Important to Know
Because splenomegaly has so many possible causes, the most important step is identifying the underlying reason and directing treatment at that condition. The clinical significance of an enlarged spleen depends entirely on what is driving it, and many causes can be effectively treated or monitored.
For congestive splenomegaly related to chronic liver disease and portal hypertension, management focuses on the underlying liver disease and the associated complications of portal hypertension, including varices and ascites, when present. Splenomegaly itself usually does not require specific treatment in this setting unless severe symptoms or specific complications develop. For splenomegaly related to heart failure or other cardiovascular causes, optimizing cardiac care is central.
For infectious causes, treatment is directed at the specific infection. Acute viral infections such as mononucleosis typically improve over weeks to months, while chronic viral, bacterial, or parasitic infections may require longer courses of specific treatment. Patients with infectious splenomegaly—particularly mononucleosis—are usually advised to avoid contact sports and other activities that could lead to abdominal trauma for a period of time, given the small risk of splenic rupture.
For hematologic conditions, treatment depends on the specific diagnosis and may include medications, transfusions, growth factors, targeted therapies, or, in selected cases, stem cell transplantation. Hemolytic anemias, sickle cell disease, thalassemias, hereditary spherocytosis, and myeloproliferative neoplasms each have their own specific approaches.
For lymphoid cancers and other malignancies, treatment is highly individualized and may include chemotherapy, immunotherapy, targeted therapies, radiation, and, in selected cases, stem cell transplantation. Care is best provided by hematologists and oncologists.
For autoimmune and inflammatory conditions, treatment focuses on the underlying disease and may include immunosuppressive or specific medications. Infiltrative and storage disorders may benefit from disease-specific therapies, including enzyme replacement therapy in certain conditions such as Gaucher disease.
Splenectomy (surgical removal of the spleen) and partial splenic embolization (a catheter-based procedure that reduces splenic blood flow) are considered in carefully selected patients—for example, those with severe symptomatic hypersplenism, certain hematologic conditions (such as immune thrombocytopenia refractory to medical therapy, hereditary spherocytosis, or selected lymphomas), specific traumatic injuries, or complications such as abscesses or large splenic cysts. Decisions are individualized and made in collaboration with hematology, surgery, and—when relevant—oncology and infectious disease.
Patients without a functioning spleen—whether due to splenectomy, congenital absence, or functional asplenia (such as in sickle cell disease)—are at increased risk of certain serious infections, particularly those caused by encapsulated bacteria. Specific vaccinations (including pneumococcal, meningococcal, and Haemophilus influenzae type b vaccines, and—when appropriate—influenza and COVID-19 vaccines), antibiotic prophylaxis in selected patients, education about prompt evaluation of fevers, and consideration of travel-related risks are essential parts of long-term care.
Care is typically coordinated by primary care clinicians, hematologists, hepatologists, infectious disease specialists, oncologists, surgeons, and other relevant providers. Imaging and laboratory findings are interpreted alongside the patient’s symptoms, examination, and broader clinical context rather than in isolation.
Patients with known splenomegaly—particularly when significant—benefit from awareness of the risk of splenic rupture from abdominal trauma and from understanding which warning signs warrant urgent evaluation.
Red flag symptoms include sudden severe upper left abdominal pain (especially after trauma to the abdomen), lightheadedness or fainting, rapid heart rate, cool clammy skin or signs of shock, signs of severe infection such as high fever and rigors, easy bruising or bleeding with severe symptoms, severe fatigue with confusion, significant unintentional weight loss with night sweats, or sudden severe shortness of breath. These warrant prompt or urgent medical evaluation, as they may indicate splenic rupture, severe infection, hematologic complications, or other serious conditions.