An enlarged spleen can cause shortness of breath, and it does so more often than many people realize. The connection works through several routes, from straightforward physical crowding of the diaphragm to subtler problems like anemia and fluid accumulation around the lungs. The severity ranges widely: a mildly enlarged spleen may produce nothing more than a vague sense of fullness after eating, while a massively swollen one can make lying flat feel suffocating.
How a Swollen Spleen Physically Restricts Breathing
The spleen sits in the upper left part of your abdomen, tucked just below the diaphragm and behind the lower ribs. In a healthy adult it weighs roughly 150 grams and measures about the size of a fist. When disease causes it to swell, sometimes to several times its normal size, it starts taking up space that neighboring organs need. The left lung base and the diaphragm are the first casualties of that expansion.
A moderately enlarged spleen may not do much beyond making you feel full early during meals or causing dull pain in the left upper abdomen. But once the spleen grows large enough to be classified as “massive splenomegaly,” typically meaning it extends well below the rib cage and sometimes across the midline of the abdomen, it exerts upward pressure on the diaphragm. The diaphragm is the main muscle you use to breathe, and anything that prevents it from dropping fully during inhalation reduces the volume of air your lungs can take in. The result is shortness of breath, especially when lying down or bending forward.
That physical crowding also raises the pressure inside the entire abdominal cavity. A case report in a patient with myelofibrosis and giant splenomegaly documented that the increased intra-abdominal pressure was directly linked to pulmonary hypertension, a condition where blood pressure in the lung arteries climbs high enough to strain the right side of the heart and make breathing difficult.1PubMed. Myelofibrosis-associated massive splenomegaly: a cause of increased intra-abdominal pressure, pulmonary hypertension, and positional dyspnea The authors emphasized that intra-abdominal pressure measurement should be part of the initial workup for patients with myelofibrosis who develop unexplained breathlessness, because it can reveal the hidden pathological link between a massive spleen and compromised lung function.
This positional element is a useful clue. People whose breathlessness worsens when they lie flat or recline but improves when they sit upright are experiencing something clinicians call orthopnea, and in the context of a known enlarged spleen, it points strongly toward mechanical compression as the culprit. The diaphragm simply cannot descend properly when a heavy organ is pressing up against it from below.
When Anemia Is the Real Culprit
The spleen’s normal job includes filtering old or damaged red blood cells out of circulation. When the spleen enlarges, it becomes overly aggressive in this filtering role, trapping and destroying red blood cells, white blood cells, and platelets faster than the body can replace them. This overactive destruction is called hypersplenism, and one of its most common consequences is anemia.
Anemia means you have fewer red blood cells carrying oxygen through your bloodstream. Your body compensates by making the heart beat faster and the lungs work harder, which you experience as feeling winded during activities that previously felt easy. Walking up a flight of stairs, carrying groceries, or even talking at length can leave you breathless. The frustrating part is that the breathlessness may creep in gradually as the anemia worsens, so some people attribute it to being out of shape or getting older rather than recognizing it as a symptom of something treatable.
This indirect route matters because it can produce shortness of breath even when the spleen is only moderately enlarged, not yet big enough to physically crowd the diaphragm. If your doctor finds an enlarged spleen and you’re feeling short of breath, a blood count is one of the first and most informative tests. Low hemoglobin in the setting of splenomegaly is a strong signal that hypersplenism is contributing to the breathing difficulty.
Fluid Around the Lungs
An enlarged or damaged spleen can also cause fluid to collect in the space between the lung and the chest wall, a condition called pleural effusion. Even a small amount of fluid in this space compresses the lung and makes it harder to expand fully. Larger collections can cause significant breathlessness, a sharp pain when breathing deeply, and a persistent cough.
One documented pathway involves the lymphatic system. The spleen connects to a network of lymphatic vessels that drain fluid from the abdomen. When the spleen is massively enlarged or ruptures, it can obstruct the posterior lymphatic channels, and the backed-up fluid finds its way into the chest cavity. A case report documented recurrent pleural effusion in a patient with splenic rupture, attributing it to this posterior lymphatic obstruction.2PubMed Central. Spontaneous Resolution of Recurrent Pleural Effusion in Atraumatic Splenic Rupture The effusion kept returning until the underlying splenic problem was addressed, highlighting that draining the fluid alone is not enough if the spleen remains the source of the blockage.
Pleural effusion from splenic causes tends to appear on the left side, which makes anatomical sense given the spleen’s location. A left-sided pleural effusion in someone with a known enlarged spleen should prompt the clinical team to consider whether the two are related, even if more common causes like heart failure or infection are also being investigated.
Liver Disease, Portal Hypertension, and the Lungs
Many of the conditions that enlarge the spleen also affect the liver, and the liver-lung connection adds another layer to how splenomegaly and breathlessness intersect. Chronic liver disease, particularly cirrhosis, frequently causes the spleen to swell because of portal hypertension, where blood pressure in the vein that drains both the intestines and the spleen rises to abnormal levels. The backed-up blood flow engorges the spleen, but the trouble does not stop there.
Portal hypertension can trigger a condition called hepatopulmonary syndrome, in which tiny blood vessels inside the lungs dilate abnormally. When those vessels widen too much, blood rushes through the lungs without spending enough time next to the air sacs to pick up oxygen efficiently. The result is low blood oxygen levels and shortness of breath that tends to worsen when standing up, a paradoxical pattern opposite to what you see with mechanical compression. A case documented in a patient with cirrhotic liver disease, splenomegaly, and portal hypertension found high cardiac output with normal pulmonary vascular resistance, findings that, combined with chronic hypoxemia, confirmed hepatopulmonary syndrome as the cause of the patient’s persistent unexplained breathlessness.3PubMed Central. Persistent Unexplained Dyspnea: A Case of Hepatopulmonary Syndrome
Hepatopulmonary syndrome is worth knowing about because it is underdiagnosed. A person with liver disease and an enlarged spleen who reports feeling short of breath is often assumed to have ascites pushing on the diaphragm or anemia from chronic illness. Those are reasonable guesses, but if the standard workup does not fully explain the degree of breathlessness, the blood-vessel dilation in the lungs should be investigated. A contrast-enhanced echocardiogram (a “bubble study”) can detect it.
Storage Disorders That Affect Both Spleen and Lungs
A less common but clinically important group of conditions links spleen enlargement and lung problems through the same underlying metabolic defect. Lysosomal storage disorders are genetic conditions in which the body lacks an enzyme needed to break down certain fats or sugars, causing those substances to accumulate inside cells. Two of these disorders stand out for their combined impact on the spleen and the lungs.
In Gaucher disease, fatty material builds up in cells of the spleen, liver, and bone marrow, causing the spleen to enlarge dramatically. Lung involvement in Gaucher disease is rare, but before enzyme replacement therapy became available in 1991, pulmonary failure was a recognized cause of death.4European Respiratory Review. Interstitial lung disease in lysosomal storage disorders Enzyme replacement therapy has changed the natural history of the disease substantially, and severe lung complications are now unusual in treated patients.
Niemann-Pick disease, also known as acid sphingomyelinase deficiency, tells a different story. Interstitial lung disease is frequent in this condition and tends to appear alongside spleen enlargement, low platelet counts, and low levels of HDL cholesterol.4European Respiratory Review. Interstitial lung disease in lysosomal storage disorders The lung disease in Niemann-Pick is not caused by the enlarged spleen pressing on the diaphragm; rather, both the spleen enlargement and the lung scarring are downstream consequences of the same enzyme deficiency. But for a patient experiencing both an enlarged spleen and worsening breathlessness, this overlap means the two symptoms share a root cause, and treating the underlying metabolic defect is the path to addressing both.
These storage disorders are individually rare, but they illustrate a broader principle: when spleen enlargement and breathing difficulty appear together, they may both be pointing at the same systemic problem rather than representing cause and effect.
Blood Clots as a Complicating Factor
An enlarged spleen can also set the stage for blood clots that directly compromise the lungs. The connection became more visible during the COVID-19 pandemic, when clinicians documented cases of patients developing splenic infarction (a blockage of blood flow within the spleen itself) alongside pulmonary embolism. One report described a 68-year-old man who came to the emergency department with shortness of breath and abdominal pain radiating to the left upper quadrant. Imaging revealed both a splenic infarction and a pulmonary embolism in the right main pulmonary artery extending into the upper and lower lobes.5PubMed Central. Splenic infarction and pulmonary embolism as a rare manifestation of COVID-19
Outside of COVID-19, the link between spleen problems and clotting is well recognized. Conditions that cause massive splenomegaly, particularly blood cancers like myeloproliferative disorders, often come with changes in blood viscosity and platelet function that raise the risk of clots forming. A clot that originates in the splenic vein or nearby vessels can travel to the lungs and cause sudden, severe shortness of breath. This is an emergency. Unlike the gradual breathlessness from diaphragm compression or slow-onset anemia, a pulmonary embolism typically produces rapid-onset shortness of breath, chest pain that worsens with breathing, and sometimes coughing up blood.
Conditions Most Likely to Cause Both Symptoms Together
Not every enlarged spleen causes breathing difficulty, and the likelihood depends heavily on the underlying disease and how large the spleen has become. Some conditions are far more prone to this overlap than others.
- Myelofibrosis: This bone marrow disorder is the classic cause of massive splenomegaly. The spleen takes over blood cell production when the marrow fails, sometimes growing to fill much of the abdomen. Breathlessness is one of the most commonly reported symptoms, driven by a combination of mechanical compression, anemia, and increased abdominal pressure.
- Chronic liver disease: Cirrhosis from alcohol, hepatitis, or fatty liver disease frequently leads to a moderately enlarged spleen through portal hypertension. Breathing problems in these patients can come from ascites pressing on the diaphragm, anemia, hepatopulmonary syndrome, or a combination of all three.
- Lymphomas and leukemias: Blood cancers often infiltrate the spleen and can cause it to enlarge significantly. The breathing difficulty may come from the enlarged spleen itself, from anemia related to the cancer’s effect on blood cell production, or from the cancer also involving the lungs or pleura.
- Infectious mononucleosis: In younger patients, mono caused by the Epstein-Barr virus commonly causes a temporarily enlarged spleen. The spleen usually does not grow large enough to compress the diaphragm, but severe cases can produce enough fatigue and malaise to make exertion feel breathless, and occasionally the associated throat swelling causes upper airway compromise rather than lower respiratory problems.
- Autoimmune conditions: Systemic lupus and rheumatoid arthritis can cause moderate spleen enlargement alongside anemia, and when lung involvement (such as pleuritis or interstitial lung disease) is also present, the two symptoms feed into each other.
The size of the spleen matters. A spleen that is mildly enlarged, say 13 to 15 centimeters on imaging, rarely causes breathing problems on its own. A spleen that has crossed into the massive category, often exceeding 20 centimeters and sometimes reaching 30 or more, is far more likely to produce both the mechanical and the systemic effects that lead to shortness of breath.
What Happens to Breathing After Treatment
If the enlarged spleen is the primary driver of the breathing difficulty, treating the spleen can produce dramatic improvement. Splenectomy, the surgical removal of the spleen, has been shown to relieve diaphragm compression, reduce intra-abdominal pressure, and resolve hypersplenism-related anemia. In patients with myelofibrosis-associated massive splenomegaly, for instance, splenectomy or splenic irradiation can reduce breathlessness quickly because the physical mass compressing the diaphragm is gone.
However, the decision to remove the spleen is never taken lightly. The spleen plays an important role in immune defense, particularly against encapsulated bacteria. People who have had their spleen removed are at lifelong increased risk of serious infections and need specific vaccinations and, in some cases, daily antibiotics. For many conditions, the underlying disease is treated first, with splenectomy reserved for cases where the spleen is causing severe symptoms or life-threatening complications like dangerously low blood counts.
Newer medications have also changed the landscape. In myelofibrosis, JAK inhibitor drugs can shrink the spleen significantly without surgery, and patients often report meaningful improvements in breathing as the spleen gets smaller. In Gaucher disease, enzyme replacement therapy reduces spleen size over months, and breathing problems linked to the disease improve in parallel. For liver disease, treating the portal hypertension with medications or procedures can reduce the engorgement of the spleen and ease both the spleen-related and the liver-related contributions to breathlessness.
Distinguishing Spleen-Related Breathlessness from Other Causes
One of the trickiest aspects of this topic is that the diseases causing spleen enlargement often have multiple other reasons to produce shortness of breath. A patient with myelofibrosis may be breathless from a massive spleen, from severe anemia, from pulmonary hypertension, or from all three at once. A patient with cirrhosis may be breathless from ascites, hepatopulmonary syndrome, anemia, or deconditioning from chronic illness. Pinning the blame on the enlarged spleen alone is rarely straightforward.
A few patterns can help sort things out. Breathlessness that worsens when lying flat and improves when sitting up suggests mechanical compression from the spleen or from ascites. Breathlessness that worsens when standing up, paradoxically, suggests hepatopulmonary syndrome. Breathlessness that is constant and proportional to activity level, without a strong positional component, points more toward anemia. And sudden-onset breathlessness with chest pain raises the alarm for pulmonary embolism, which needs urgent evaluation regardless of what is happening with the spleen.
If you have a known enlarged spleen and notice new or worsening shortness of breath, it is worth bringing up with your doctor even if the breathlessness seems mild. The spleen-lung connection is real, but because it works through several different mechanisms, identifying the right one matters for choosing the right treatment. A simple blood count to check for anemia, imaging to assess spleen size and look for fluid around the lungs, and sometimes specialized tests like a bubble study for hepatopulmonary syndrome can clarify what is driving the symptom and how best to address it.