Yes, COVID-19 can cause the spleen to enlarge. CT imaging studies have documented measurable increases in spleen size during the course of infection, with average splenic volume rising from about 244 cm³ at initial scan to roughly 304 cm³ on follow-up. The enlargement appears to result from the intense immune response COVID triggers, and in some cases, from direct viral damage to splenic tissue.
How COVID-19 Affects the Spleen
The spleen is a fist-sized organ tucked under your left ribcage. It filters blood, recycles old red blood cells, and plays a central role in immune defense. It’s packed with immune cells organized into zones called white pulp (where infection-fighting cells gather) and red pulp (where old blood cells are broken down). COVID-19 appears to affect both.
SARS-CoV-2 has a particular affinity for the spleen, especially its white pulp. The virus likely gains entry through ACE-2 receptors on the surface of splenic cells, the same receptors it uses to infect the lungs. Autopsy studies have revealed white pulp atrophy in COVID patients, meaning the clusters of immune cells that normally populate the spleen shrink or disappear. Lymphoid follicles, the organized structures where immune cells multiply and coordinate their response, were reduced or entirely absent in some cases.
At the same time, the spleen can swell. This may seem contradictory: the immune tissue inside is shrinking while the organ itself gets bigger. But the enlargement likely comes from a combination of increased blood flow, congestion in the red pulp, microthrombosis (tiny blood clots forming in the spleen’s blood vessels), and the accumulation of inflammatory cells flooding the organ during the body’s immune response.
The Role of Immune Overreaction
In severe COVID-19, the immune system can spiral into a state of hyperinflammation sometimes compared to a condition called macrophage activation syndrome (MAS). In MAS, certain immune cells (T cells and macrophages) become overactivated and multiply excessively. Instead of clearing the infection and standing down, they keep producing inflammatory signals, creating a feedback loop. This process is marked by extremely high ferritin levels, drops in blood cell counts, liver dysfunction, and clotting problems. Spleen enlargement is a recognized feature of this syndrome.
In COVID-19, a similar pattern of immune overactivation can drive splenic changes. The spleen becomes a site of intense immune activity, swelling as it processes the flood of activated immune cells and inflammatory debris. This is more common in critically ill patients, but measurable increases in spleen dimensions have been documented across a range of COVID severity levels.
How Much the Spleen Changes
A study published in Clinical Imaging tracked spleen measurements in COVID-19 patients across initial and follow-up CT scans. The average craniocaudal length (the top-to-bottom measurement) increased from about 97 mm to 108 mm. Thickness grew from roughly 41 mm to 45 mm. The overall splenic index, a composite measure combining all three dimensions, jumped from about 421 cm³ to 523 cm³, representing a roughly 24% increase.
For context, a normal spleen is typically around 12 cm long. These measurements suggest that while many COVID patients’ spleens stayed within normal range at initial presentation, they grew meaningfully over the course of infection. Some patients’ spleens crossed into the range that would be classified as splenomegaly (clinical enlargement).
Splenic Infarction: A Rarer but Serious Risk
Beyond simple enlargement, COVID-19 can cause splenic infarction, where blood clots block flow to part of the spleen, killing a section of tissue. This is uncommon but worth knowing about. In critically ill COVID patients, around 31% experienced some form of thrombotic complication even while receiving blood-thinning treatment. While most of those clots were in veins (particularly the lungs), about 4% were arterial events, and some of those affected the spleen.
Symptoms of splenic infarction include tenderness or pain in the left upper abdomen, fever, nausea, and vomiting. In reported COVID cases, patients described moderate to severe abdominal pain lasting days, sometimes accompanied by chills, rash, or loss of appetite. Some patients had no abdominal pain at all and presented only with respiratory symptoms like cough and shortness of breath, making it easy to miss.
On CT imaging, splenic infarction shows up as wedge-shaped areas of low density within the spleen, or broader patches of reduced blood flow visible on CT angiography. Spontaneous splenic rupture, while extremely rare, has also been documented in COVID patients and can cause dangerous internal bleeding.
Can EBV Reactivation Play a Role?
There is growing interest in whether COVID-19 can reactivate dormant viruses like Epstein-Barr virus (EBV), the virus responsible for mono. Most adults carry EBV in a latent state, and the inflammation triggered by COVID may wake it up. EBV reactivation is a well-known cause of spleen enlargement on its own, so if COVID triggers it, the two infections could compound splenic effects.
Research has suggested a connection between COVID-induced inflammation and EBV reactivation, and at least one case report described an EBV-related splenic tumor that appeared to be activated by COVID infection and its long-term aftereffects. This remains an area where the evidence is preliminary, but it offers one possible explanation for splenic enlargement that persists or worsens after the acute COVID infection has resolved.
What Enlarged Spleen Feels Like
Many people with a mildly enlarged spleen feel nothing at all. It’s often discovered incidentally on imaging done for other reasons, like a chest CT that captures the upper abdomen. When the spleen is large enough to cause symptoms, you might notice a sense of fullness or discomfort under your left ribs, especially after eating. Some people feel full quickly during meals because the enlarged spleen presses against the stomach.
If the spleen is significantly swollen, it can become tender to the touch. Pain that is sharp, sudden, and localized to the left upper abdomen, particularly if it radiates to the left shoulder, could indicate infarction or rupture and needs urgent evaluation.
How It’s Detected
Doctors typically identify an enlarged spleen through CT scans or ultrasound. In COVID patients, CT imaging of the chest often extends low enough to capture the spleen, which is how many cases are first noticed. On CT, enlargement appears as an increase in overall organ dimensions. When infarction is present, the scan shows characteristic wedge-shaped or patchy areas where blood flow has been cut off. Ultrasound can also measure spleen size and detect areas of abnormal texture, though CT provides more detailed information about blood vessel involvement.
There is no specific treatment for COVID-related spleen enlargement on its own. The swelling typically reflects the underlying immune response, and as the infection resolves, the spleen is expected to return toward its normal size. If splenic infarction is identified, blood-thinning therapy may be adjusted. In extremely rare cases involving rupture, surgical intervention is necessary.