An enlarged spleen is almost never a problem that starts in the spleen itself. It is a sign that something else is going on — an infection, a liver condition, a blood disorder, or another underlying disease. The spleen reacts to that problem by holding onto more blood cells and immune tissue than usual, and it grows larger as a result. Doctors call an enlarged spleen splenomegaly, and finding the cause matters more than treating the size itself.
The spleen sits in the upper left part of your abdomen, tucked behind the stomach and below the rib cage. It normally weighs about 150 grams (roughly 5 to 7 ounces) and is about the size of a fist. In healthy adults it is usually too small to feel through the belly wall. When it enlarges, it can become palpable below the rib cage on the left side — and in some cases it grows large enough to press on nearby organs.
What Causes An Enlarged Spleen?
There is no single cause. Splenomegaly is a finding with a long list of possible explanations, and the most likely one depends heavily on your age, where you live, your travel history, and whether you have other symptoms or known medical conditions.
Broadly, the causes fall into a few categories based on what the spleen is doing:
- Increased workload filtering blood cells. The spleen removes old or damaged red blood cells. In conditions where red cells are destroyed faster than normal — such as hereditary spherocytosis or autoimmune hemolytic anemia — the spleen works harder and enlarges.
- Infection. The spleen is part of the immune system and responds to infections by producing immune cells. Viral infections such as Epstein-Barr virus (the virus that causes mononucleosis) are a common cause in young adults. Malaria is one of the most common causes worldwide. Other infections, including certain bacterial infections and endocarditis, can also enlarge the spleen.
- Liver disease. Cirrhosis and other conditions that raise pressure in the portal vein — the large vein that carries blood from the digestive organs to the liver — cause blood to back up into the spleen. This is called portal hypertension, and it is one of the more common causes of splenomegaly in adults in the United States.
- Blood cancers and other cancers. Leukemias, lymphomas, and myeloproliferative disorders can cause the spleen to enlarge as abnormal blood cells accumulate or as the spleen becomes involved in the disease.
- Storage and infiltrative diseases. Conditions such as Gaucher disease, amyloidosis, and certain rare metabolic disorders cause material to build up in the spleen.
- Blood clots in the splenic vein. A blockage in the vein draining the spleen can cause it to swell.
Some causes are far more common than others, and the pattern differs by age. In children and young adults, infections — especially viral ones — are frequent culprits. In older adults, liver disease and blood cancers become more likely.
How Do You Know If Your Spleen Is Enlarged?
Many people with a mildly enlarged spleen have no symptoms at all. It is often found by accident during a physical exam or an imaging test done for another reason.
When symptoms do appear, they tend to come from the spleen pressing on nearby structures or from the underlying condition itself. Common ones include:
- A feeling of fullness or discomfort in the upper left abdomen
- Pain in the left upper belly that may spread to the left shoulder
- Feeling full quickly after eating, because the spleen can press on the stomach
- Fatigue, which is often related to the underlying cause rather than the spleen itself
- Frequent infections or easy bleeding and bruising, if the spleen is trapping too many blood cells
Doctors confirm the size with imaging. Ultrasound is usually the first test. CT or MRI may be used to get a clearer picture and to look for causes such as liver disease or enlarged lymph nodes. Blood tests can point toward infection, anemia, or a blood disorder.
One point worth knowing: a spleen that can be felt below the left rib cage is not automatically abnormal in every person. Body shape and breathing can affect whether a normal spleen becomes palpable. Imaging resolves the question.
What Does an Enlarged Spleen Do to Your Blood?
An enlarged spleen can trap and destroy more blood cells than it should. This is called hypersplenism, and it is one of the most important consequences of splenomegaly.
When the spleen over-filters, it can lower the number of red blood cells (causing anemia), white blood cells (raising infection risk), and platelets (raising bruising and bleeding risk). Blood tests can show these changes even when a person feels fine.
This is why doctors often monitor blood counts over time in people with a known enlarged spleen. The size itself may not need treatment, but the effect on blood counts can matter.
When Is an Enlarged Spleen a Medical Emergency?
A very enlarged spleen can rupture, especially after trauma. Rupture is uncommon, but it is serious and can be life-threatening because of internal bleeding.
Seek emergency care if you have a known or suspected enlarged spleen and develop sudden, severe pain in the upper left abdomen, especially after a fall, a car accident, or a blow to the body. Dizziness, fainting, a rapid heartbeat, or pain spreading to the left shoulder are warning signs.
People with a significantly enlarged spleen are usually advised to avoid contact sports and activities with a high risk of abdominal impact. This is common clinical advice, though the exact size threshold at which restriction becomes necessary is not firmly established and varies by clinician.
How Is an Enlarged Spleen Treated?
Treatment targets the underlying cause, not the spleen size by itself. That is the central principle. An enlarged spleen from mononucleosis will usually shrink on its own as the infection clears. Splenomegaly from cirrhosis is managed by treating the liver disease and its complications. A blood cancer is treated with the appropriate cancer therapy.
In some cases, removing the spleen (splenectomy) is considered. This is done when the spleen is causing serious problems — such as dangerously low blood counts, repeated rupture risk, or severe pain — and when other options have not worked. Splenectomy is major surgery and has lifelong consequences, including a higher risk of certain infections. People who have their spleen removed generally need vaccinations and, in some cases, preventive antibiotics. Those decisions are made with a specialist.
Partial splenic embolization — a procedure that reduces blood flow to part of the spleen — is another option some centers use for selected patients. It is not appropriate for everyone, and outcomes vary.
What Should You Do If You Notice Symptoms?
See a doctor if you have persistent pain or fullness in the upper left abdomen, unexplained fatigue, easy bruising, or frequent infections. These symptoms have many possible causes, and an enlarged spleen is only one of them.
Tell your doctor about recent travel, especially to areas where malaria is common, and about any known liver disease, blood disorders, or family history of inherited conditions. That context helps narrow the search.
Avoid guessing at the cause. Splenomegaly is a sign, and the work of finding what it points to is best done with proper testing.
Frequently Asked Questions
Can an enlarged spleen go back to normal?
Yes, in many cases. When the underlying cause is treated or resolves — such as an infection clearing — the spleen often returns to its normal size. Some chronic conditions cause lasting enlargement.
Is an enlarged spleen serious?
It depends entirely on the cause. Some cases are temporary and harmless, while others point to a condition that needs treatment. The size alone does not tell you how serious it is.
What are the first signs of an enlarged spleen?
Many people have no symptoms. When symptoms appear, the most common is a feeling of fullness or pain in the upper left abdomen, sometimes spreading to the left shoulder.
Can an enlarged spleen cause fatigue?
Fatigue is common but usually comes from the underlying condition or from anemia caused by the spleen trapping red blood cells, not from the enlarged spleen itself.
