Pain in the area of your spleen, a fist-sized organ tucked inside your left rib cage just above your stomach, usually signals that the spleen is enlarged, injured, or that something nearby is irritating it. The cause can range from a common viral infection to something more serious like a blood clot or trauma. Where the pain is, how it started, and what other symptoms you have all help narrow down what’s going on.
Where Spleen Pain Actually Shows Up
Because the spleen sits behind your lower left ribs, pain from it tends to concentrate in the upper left part of your abdomen. You might feel it as a dull fullness or pressure under your ribs, or as a sharper pain that gets worse when you breathe deeply or press on the area.
One distinctive pattern: spleen problems can also cause pain in your left shoulder. This happens because irritation near the spleen (from swelling, bleeding, or a blood clot) affects the phrenic nerve, which runs along the diaphragm. The nerve refers the sensation up to the shoulder even though nothing is wrong with the shoulder itself. If you have upper left abdominal pain and left shoulder pain together, the spleen is a strong suspect.
An Enlarged Spleen Is the Most Common Cause
The spleen filters blood and helps fight infections, which means it swells up when your body is dealing with certain illnesses. An enlarged spleen (called splenomegaly) is the most frequent reason for spleen-area pain. It often feels like a dragging fullness under your left ribs, and you may feel full quickly when eating because the swollen spleen presses against your stomach.
A spleen is considered mildly enlarged at around 14 centimeters (normal size varies by your height, age, and sex). Mild enlargement on its own often isn’t dangerous, but anything significantly beyond that threshold raises concern about an underlying condition that needs attention.
Infections
Viral infections are one of the most common triggers. Infectious mononucleosis (mono), caused by the Epstein-Barr virus, is a classic example. Mono makes the spleen swell noticeably, and the enlargement typically peaks within the first three weeks of symptoms. Bacterial infections like endocarditis (an infection of the heart’s inner lining) and parasitic infections like malaria can also cause the spleen to enlarge.
Liver Disease
When the liver is scarred or congested, blood backs up into the spleen through the portal vein. This congestion forces the spleen to swell. If you have known liver problems or risk factors for liver disease, that backup pressure is a likely explanation for spleen pain.
Blood Disorders and Cancers
The spleen filters and recycles old or damaged blood cells. In conditions where the body produces abnormal blood cells or destroys them too quickly, the spleen works overtime and enlarges as cells accumulate inside it. Blood cancers like leukemia and lymphoma can do this, as can various forms of anemia where red blood cells break down faster than normal. Pain from these causes tends to build gradually rather than appearing suddenly.
Blocked Blood Flow to the Spleen
A splenic infarction occurs when a blood clot blocks the artery supplying the spleen, killing a patch of tissue. The hallmark is sudden, severe pain in the upper left abdomen that may radiate to your left shoulder. It’s a sharp, unmistakable pain, very different from the dull ache of an enlarged spleen.
Several conditions raise the risk of this happening. Blood-clotting disorders like protein C or protein S deficiency make clots more likely. Sickle cell disease, where misshapen red blood cells can jam blood vessels, is another common cause. Heart conditions, particularly atrial fibrillation and congestive heart failure, can generate clots that travel to the spleen. If you have any of these conditions and develop sudden left-sided abdominal pain, a splenic infarction is something to consider urgently.
Trauma and Rupture
A blow to the left side of your body, whether from a car accident, a fall, a sports collision, or even a fistfight, can injure or rupture the spleen. This is one of the more dangerous causes of spleen pain because a ruptured spleen bleeds into the abdominal cavity.
What makes this tricky is the timing. The spleen can rupture immediately after an impact, but it can also rupture days or even weeks later. So if you took a hard hit to your left side recently and are now feeling pain there, don’t dismiss it just because the injury wasn’t recent.
An already-enlarged spleen is especially vulnerable. If you have mono or another condition that’s made your spleen swell, even relatively minor contact can cause a rupture. This is exactly why the CDC recommends avoiding contact sports entirely until you’ve fully recovered from mono. About 80% of mono-related spleen ruptures happen within the first three weeks of symptom onset, which is the highest-risk window.
Signs That Need Immediate Attention
Most spleen pain turns out to be related to a treatable infection or a temporary condition. But certain combinations of symptoms point to something more dangerous, particularly internal bleeding from a rupture. Watch for:
- Confusion, lightheadedness, or dizziness alongside left-sided abdominal pain, which can signal blood loss
- Left shoulder pain combined with abdominal tenderness, especially after any kind of physical trauma
- Tenderness that worsens when you touch or press on your upper left abdomen
- Sudden severe pain that comes on without warning, which may indicate a blood clot or rupture
If you’re experiencing pain under your left ribs that’s mild, doesn’t come with any of these warning signs, and you’ve recently been sick with something like mono or another infection, the most likely explanation is temporary spleen swelling that will resolve as the infection clears. But pain in this area that persists for more than a few days, worsens, or appears alongside dizziness or shoulder pain warrants imaging. An ultrasound can quickly measure spleen size and check for structural problems, and it’s typically the first test ordered.