Updated on October 19, 2026 · Our editorial process
An enlarged spleen is one of those findings that often turns up by accident. A doctor presses under your left ribs during a routine exam, or an ultrasound ordered for something else shows the spleen is bigger than it should be. Sometimes there are no symptoms at all. Other times there is a dull ache or a strange feeling of being full after three bites of dinner.
The important thing to understand is that an enlarged spleen is not a disease. It is a sign. Something else, usually an infection, a liver problem, or a blood disorder, is making the spleen work harder or hold more blood than normal. This guide covers the symptoms, the causes in order of how common they are, how doctors find the reason, how it is treated, and the one precaution everyone with an enlarged spleen needs to take.
Key takeaways
- The medical name is splenomegaly. A normal adult spleen is about 4 to 5 inches long and cannot be felt. An enlarged one often can.
- Many enlarged spleens cause no symptoms. When they do, the signs are pain or fullness under the left ribs, feeling full after small meals, tiredness from anemia, frequent infections, and easy bruising.
- The common causes are infections such as mononucleosis, liver disease such as cirrhosis, and blood disorders or blood cancers. Treating the cause usually shrinks the spleen.
- An enlarged spleen tears more easily. Avoid contact sports and heavy impact until your doctor says it has returned to normal size.
- Sudden severe pain under the left ribs, with dizziness or a racing heart, is an emergency.
What counts as an enlarged spleen?
The spleen sits in the upper left of your abdomen, under the ninth to eleventh ribs, behind the stomach. In a healthy adult it is roughly the size of your fist, about 4 to 5 inches long, and the rib cage hides it completely. Doctors call it enlarged when it grows past about 5 inches, or 12 to 13 centimeters, on an ultrasound, or when it has grown far enough down and forward that it can be felt below the ribs. A spleen that can be felt is usually at least one and a half times its normal size.
Enlargement happens for three basic reasons. The spleen is fighting an infection and fills with immune cells. It is clearing abnormal blood cells and swells with the extra work. Or blood is backing up into it because it cannot flow freely through the liver. Which of those is going on decides the treatment, which is why finding the cause matters more than the size itself. If you want the basics of what the organ does first, our guide to spleen function and location covers it.
Enlarged spleen symptoms
According to the Mayo Clinic, an enlarged spleen often causes no symptoms and is discovered during a routine physical. When it does cause symptoms, they come from two things: the size of the spleen pressing on its neighbors, and the spleen removing too many blood cells.
Symptoms from the size
- Pain or fullness under the left ribs. Usually a dull ache or pressure rather than a sharp pain. It can spread to the left shoulder, because the diaphragm above the spleen shares a nerve with the shoulder. Deep breaths can make it worse.
- Feeling full after a few bites. The spleen sits right against the stomach, and a swollen spleen leaves less room for food. Many people lose weight without trying because of this.
- A visible or feelable lump under the left ribs in very large spleens.
Symptoms from the blood cells
- Tiredness, breathlessness, and pale skin from anemia, when the spleen removes too many red blood cells.
- Frequent infections, especially chest infections, when white blood cells are low.
- Easy bruising, bleeding gums, or nosebleeds when platelets are trapped in the spleen.
Those blood cell symptoms have a name of their own, hypersplenism, and they are often what prompts the blood test that finds the problem. For a detailed look at how spleen pain feels and how to tell it from other left-sided pain, see our guide to spleen pain, its location, and when to worry.
What causes an enlarged spleen?
The list of causes is long, but a handful account for most cases. The Cleveland Clinic groups them the same way doctors think about them.
Infections
The classic cause in teenagers and young adults is mononucleosis, the Epstein-Barr virus infection that brings a sore throat, swollen glands, and weeks of exhaustion. Around half of people with mono develop a swollen spleen. Other viral causes include cytomegalovirus, hepatitis, and HIV. Bacterial causes include endocarditis, an infection of the heart’s lining, tuberculosis, and syphilis. In parts of the world where they are common, malaria and leishmaniasis are leading causes of very large spleens.
Liver disease
Blood leaving the spleen flows through the portal vein into the liver. When the liver is scarred by cirrhosis or chronic hepatitis, pressure in that vein rises and blood backs up into the spleen, which swells. This is one of the most common causes in adults in the US and the UK, and it is often tied to alcohol or to fatty liver disease. In these cases, protecting the liver is how you protect the spleen, and our guide to the best foods for spleen health and the foods to avoid with an enlarged spleen is built around that.
Blood disorders
In hemolytic anemias, sickle cell disease, and thalassemia, red blood cells break down early and the spleen swells with the work of clearing them. In sickle cell disease the picture changes with age: children can have a dangerously swollen spleen, while adults often have a spleen that has shrunk and stopped working from repeated damage.
Blood cancers and bone marrow disorders
Leukemia, lymphoma, and myeloproliferative conditions such as myelofibrosis and polycythemia vera cause abnormal cells to collect in the spleen. Some of the largest spleens doctors see come from these conditions. This is the group everyone worries about, and it is worth saying that it is far from the most common cause, but it is the reason an enlarged spleen is always investigated rather than watched.
Other causes
- Autoimmune conditions such as lupus, rheumatoid arthritis, and sarcoidosis
- Inherited metabolic diseases such as Gaucher disease and Niemann-Pick disease
- Heart failure, which raises pressure in the veins
- A blood clot in the splenic or portal vein
- A cyst or abscess inside the spleen, which is uncommon
How doctors diagnose it
It usually starts with the exam. The doctor presses under your left ribs while you breathe in, feeling for the edge of the spleen as it moves down. From there:
- A full blood count shows whether red cells, white cells, or platelets are low, and can point toward infection, anemia, or a blood cancer.
- Liver function tests and tests for infection, including mono, hepatitis, and HIV where appropriate.
- An ultrasound measures the spleen accurately in a few minutes and checks the liver at the same time. A CT or MRI scan gives more detail if needed.
- Further tests only if the first round does not explain it: a bone marrow test if a blood cancer is suspected, or specific tests for autoimmune and inherited conditions.
The NHS notes that in most people the cause is found with these standard tests and the spleen itself needs no treatment.
How an enlarged spleen is treated
There is no treatment for the spleen on its own. Treatment is aimed at the cause, and when the cause is dealt with, the spleen almost always shrinks back on its own.
- Mononucleosis and other viral infections settle with rest and time, usually over several weeks.
- Bacterial and parasitic infections are treated with antibiotics or antiparasitic medicines.
- Liver disease is managed by treating its cause, stopping alcohol, and reducing pressure in the portal vein where needed.
- Blood disorders and cancers are treated by a hematologist, and the spleen shrinks as the condition is brought under control.
- Splenectomy, surgical removal, is reserved for cases where the spleen is destroying too many blood cells and the cause cannot be controlled, or where it has ruptured. People who have it removed live normally but carry a lifelong higher risk of serious infections, so they need specific vaccines and sometimes daily antibiotics. Our guide to living without a spleen explains what changes.
The one precaution everyone needs: protect it from injury
A normal spleen is tucked safely behind the ribs. An enlarged one has grown down below them, it is softer than normal, and its covering is stretched thin. That makes it far easier to tear. A ruptured spleen bleeds heavily into the abdomen and is a medical emergency.
For as long as your spleen is enlarged, and until your doctor confirms it is back to normal size:
- No contact sports: football, soccer, rugby, hockey, basketball, martial arts, wrestling.
- No heavy lifting or straining.
- Wear a seat belt, and be careful with anything that could deliver a blow to the left side.
After mono, that usually means at least three to four weeks away from sport, and longer if a scan still shows enlargement. Teenagers and athletes find this the hardest advice to follow, and it is the advice that matters most.
When to see a doctor, and when to go to the emergency room
See your doctor within a few days if you have steady aching or fullness under your left ribs, feel full after small meals, are unusually tired or pale, keep getting infections, or bruise easily. These are reasons for a blood test and an ultrasound, not reasons to panic.
Go to the emergency department, or call emergency services, if you have sudden severe pain in the upper left abdomen, especially after a fall, a tackle, or a car accident, or if that pain comes with pain at the tip of the left shoulder, dizziness, fainting, confusion, or a fast heartbeat. Those are the signs of a rupture and internal bleeding. The NHS points out that a damaged spleen can rupture days or even weeks after the original knock, so mention any recent injury even if it seemed minor.
Living with an enlarged spleen
While the cause is being treated, a few things make life easier. Eat smaller meals more often if you fill up quickly, and keep protein and iron in them so you do not lose muscle along with the weight. Report new tiredness, bruising, or infections promptly, because they can mean your blood counts have dropped. Keep your vaccines current, including the yearly flu shot. And keep every follow-up scan, because the size of the spleen is one of the clearest signs of whether the underlying treatment is working.
The bottom line
An enlarged spleen is a sign, not a disease. The usual culprits are an infection like mono, liver disease, or a blood disorder, and the spleen shrinks back once that is treated. Many people have no symptoms; others notice fullness or ache under the left ribs, early fullness when eating, tiredness, infections, or bruising. The single most important thing to do while it is enlarged is to protect it from a blow, because a swollen spleen tears easily and a rupture is an emergency.
Frequently asked questions
What are the first signs of an enlarged spleen?
Often there are none and it is found during an exam or scan. When there are early signs, the most common are a dull ache or sense of fullness under the left ribs, feeling full after eating only a little, and tiredness. Pain at the left shoulder tip can also occur because the spleen irritates the diaphragm.
What is the most common cause of an enlarged spleen?
In teenagers and young adults, mononucleosis. In adults overall, liver disease such as cirrhosis, which forces blood to back up into the spleen, and blood disorders. Blood cancers are a less common but important cause, which is why an enlarged spleen is always investigated.
Can an enlarged spleen go back to normal?
Yes, in most cases. Once the infection clears or the underlying condition is treated, the spleen shrinks back over weeks to months. Spleens enlarged by long-term liver disease or chronic blood disorders may stay larger than normal for as long as the condition lasts.
Is an enlarged spleen serious?
The enlargement itself is usually not dangerous, but the cause can be, and an enlarged spleen is more likely to rupture after a blow. That is why it is investigated with blood tests and a scan, and why contact sports are off limits until it returns to normal size.
What should you not do with an enlarged spleen?
Avoid contact sports, heavy lifting, and anything that risks a blow to the left side, until your doctor confirms the spleen is back to normal. Limit alcohol, since liver strain makes the spleen worse. Do not ignore new tiredness, bruising, or infections, and do not skip follow-up scans.
What foods help an enlarged spleen?
No food shrinks the spleen directly. What helps is a diet that protects the liver and supports healthy blood: vegetables, fruit, whole grains, fish, beans, and lean protein, with alcohol, sugary drinks, and ultra-processed food kept low. Iron-rich foods matter if you are anemic. Our spleen foods guide covers this in detail.
How long does an enlarged spleen last after mono?
Usually two to four weeks after symptoms begin, though it can take longer. Doctors advise staying out of contact sports for at least three to four weeks from the start of the illness and until an exam or scan confirms the spleen is back to normal, because it can rupture with a knock during that time.
Can you feel an enlarged spleen yourself?
Sometimes, if it is very large, as a firm lump under the left ribs or a fullness when you press there. Most enlarged spleens are not obvious from the outside, which is why a doctor’s exam and an ultrasound are the reliable ways to know.
