Tucked away in the upper left side of the abdomen, the spleen is a hard-working but often overlooked organ. Most people are unaware of its vital roles in filtering our blood and supporting our immune system. It is usually only when the spleen becomes enlarged, a condition known as splenomegaly, that it comes to our attention. An enlarged spleen is not a disease in itself, but rather a significant clinical sign that the body is grappling with an underlying medical problem. This could be an infection, liver disease, blood disorder or other serious condition.  Therefore, discovering that you have an enlarged spleen is the beginning of a medical investigation to uncover the root cause, which is crucial for protecting your long-term health.

Splenomegaly refers to an enlarged spleen, a condition where the spleen becomes larger than its normal size. In a healthy adult, the spleen is the size of a fist and weighs around 150 grams. It cannot usually be felt during a physical examination. When certain diseases cause the spleen to swell and grow larger than its normal size, it is called splenomegaly. If it becomes large enough, a doctor may be able to feel it during an abdominal exam.

To understand why the spleen might enlarge, it is essential to first understand its two main jobs. The spleen is effectively a combination of a high-tech immune surveillance center and a sophisticated blood filtration plant.

• Immune Function (The White Pulp): The spleen is a major component of the lymphatic system. It produces lymphocytes (a type of white blood cell) and acts as a key line of defense against certain types of bacteria, particularly “encapsulated” bacteria like Streptococcus pneumoniae and Neisseria meningitidis.
• Blood Filtration (The Red Pulp): The spleen acts as a quality-control filter for the blood. It contains a network of narrow passages through which blood must squeeze. Healthy, flexible red blood cells can pass through, but old, damaged, or abnormally shaped red blood cells are trapped and destroyed. The spleen also removes old platelets and certain bacteria from the bloodstream.

Splenomegaly occurs when the spleen is forced to work in extreme overdrive or when it becomes infiltrated by abnormal cells. For example, a major infection can cause the spleen’s immune functions to ramp up dramatically. A blood disorder with fragile red blood cells can cause the spleen’s filtration function to become massively overworked as it removes the damaged cells. Cancers like leukemia or lymphoma can directly invade the spleen with malignant cells. In each case, the result is a congested, overworked, and enlarged organ.

A major complication of a significantly enlarged spleen is hypersplenism. This is a condition where the overactive, enlarged spleen begins to trap and destroy not only old blood cells but healthy ones as well. This can lead to a shortage of all three types of blood cells in the bloodstream (pancytopenia): anemia (low red cells), leukopenia (low white cells), and thrombocytopenia (low platelets).

I’ve seen many cases where splenomegaly was discovered accidentally during imaging. It often points us toward hidden infections, liver problems, or blood disorders we wouldn’t have caught otherwise.

An enlarged spleen is always a consequence of an underlying disease process. The list of potential causes is extensive and covers a wide range of conditions, from common infections to rare blood disorders.

The causes can be grouped into several main categories:

1. Infections

When the body is fighting a significant infection, the spleen’s immune activity increases, causing it to enlarge temporarily.

• Viral Infections: Infectious mononucleosis, caused by the Epstein-Barr virus, is a classic cause of splenomegaly in young adults. Cytomegalovirus (CMV) and HIV can also be culprits.
• Bacterial Infections: Any severe systemic infection (sepsis) can cause the spleen to enlarge. Specific infections include infective endocarditis (an infection of the heart valves) and tuberculosis (TB) that has spread beyond the lungs.
• Parasitic Infections: In many parts of the world, certain parasitic infections are a leading cause of massive splenomegaly. These include malaria and leishmaniasis (kala-azar).

2. Liver Disease and Portal Hypertension

This is one of the most common causes of splenomegaly.

• The portal vein is a major blood vessel that carries blood from the digestive system and the spleen to the liver. In conditions that cause severe liver scarring, like cirrhosis, this blood flow is blocked.
• This blockage causes the pressure in the portal vein to rise dramatically (a condition called portal hypertension).
• The high pressure causes blood to back up into the spleen, leading to significant congestion and enlargement. This is known as congestive splenomegaly. The most common causes of cirrhosis worldwide include chronic Hepatitis B, chronic Hepatitis C, and alcoholic liver disease.

3. Hematologic (Blood) Disorders

• Hemolytic Anemias: These are conditions where red blood cells are destroyed prematurely. The spleen enlarges as it works overtime to clear the fragments of these destroyed cells. This is a key feature of inherited conditions like hereditary spherocytosis and thalassemia major.
• Cancers of the Blood and Lymphatic System: Cancers like leukemia (particularly chronic lymphocytic leukemia and chronic myeloid leukemia) and lymphoma (both Hodgkin and non-Hodgkin) can directly infiltrate the spleen with cancerous cells, often causing massive enlargement.
• Myeloproliferative Neoplasms: These are a group of disorders where the bone marrow produces too many of a certain type of blood cell. Conditions like polycythemia vera and myelofibrosis are classic causes of splenomegaly.

4. Inflammatory and Autoimmune Diseases

Systemic inflammatory conditions like rheumatoid arthritis and systemic lupus erythematosus (lupus) can also cause the spleen to enlarge.

One patient had splenomegaly caused by untreated hepatitis C. It wasn’t until we looked at the spleen that we started uncovering the broader picture of liver disease.

You “get” splenomegaly due to another health issue. Therefore, the risk factors for splenomegaly are the risk factors for these various conditions.

You may be at a higher risk of developing splenomegaly if you:

• Live in or travel to an area where malaria or leishmaniasis are endemic.
• Have chronic viral hepatitis (B or C) or another form of chronic liver disease.
• Have a known inherited blood disorder like thalassemia or sickle cell disease.
• Have a diagnosed hematologic cancer like leukemia or lymphoma.
• Have a systemic autoimmune disease like lupus.

In many cases, patients don’t feel anything unusual. It’s during routine exams or scans for another reason that we find out the spleen is enlarged.

Small to moderate splenomegaly may not cause any symptoms. A doctor often discovers it during a routine physical examination or on an imaging scan performed for another reason.

When an enlarged spleen does cause symptoms, they are usually due to its size and its pressure on surrounding organs, or due to the effects of hypersplenism.

Symptoms directly related to the enlarged spleen can include:

• A vague feeling of pain, discomfort, or fullness in the upper left part of the abdomen.
• The pain can sometimes radiate to the left shoulder. This is known as Kehr’s sign and is caused by the enlarged spleen irritating the diaphragm.
• Early satiety, which is a feeling of getting full very quickly after eating only a small amount of food. This happens because the enlarged spleen is pressing on the stomach.
• Hiccups that are persistent and difficult to resolve, also due to diaphragm irritation.

If the enlarged spleen leads to hypersplenism (the over-destruction of blood cells), the symptoms will be those of low blood counts:

• Fatigue, weakness, and shortness of breath from anemia.
• Frequent or recurrent infections from a low white blood cell count.
• Easy bruising or bleeding from a low platelet count.

Often, the most prominent symptoms a person experiences are those of the underlying disease causing the splenomegaly, such as the fever and chills of malaria or the jaundice of liver disease.

One clue is a patient saying, “I can’t eat much before I feel full.” When I hear that along with fatigue or anemia, I always think to check the spleen.

An enlarged spleen is always a significant clinical finding that requires a thorough medical workup to identify the root cause.
The diagnostic process is a stepwise investigation led by a physician.

1. Physical Examination: The first clue is often a doctor feeling the tip of the spleen during an abdominal exam. A normal spleen cannot be felt, so a palpable spleen is always an abnormal finding.
2. Imaging:
   • Abdominal Ultrasound: This is usually the first imaging test ordered. It is a simple way to confirm that the spleen is enlarged.
   • Computed Tomography (CT) Scan: A CT scan provides more detailed images of the spleen and all the surrounding abdominal organs.
3. Blood Tests: A comprehensive set of blood tests is essential for narrowing down the cause.
   • A Complete Blood Count (CBC) is performed to check for anemia, low white cells, or low platelets (signs of hypersplenism) or abnormally high counts.
   • A Peripheral Blood Smear is performed to check for abnormal shapes (as in hemolytic anemias) or signs of malaria parasites.
   • Liver Function Tests (LFTs) are done to check for liver disease.
   • Other specific blood tests may be ordered to look for antibodies related to autoimmune diseases or evidence of specific infections.
4. Bone Marrow Biopsy: May be needed if a blood cancer or other bone marrow disorder is suspected.

I always emphasize to patients that an enlarged spleen isn’t a final answer, it’s a signpost that leads us toward what’s really going on.

Treatment focuses on addressing the underlying cause of the splenomegaly. The spleen itself is usually not the direct target of therapy unless it becomes dangerously enlarged or at risk of rupture.

• For Infections: Treatment with the appropriate antibiotics, antiparasitic drugs, or antiviral medications will resolve the infection.
• For Liver Disease: Management is focused on treating the underlying liver condition and managing the complications of portal hypertension.
• For Cancers: Treatment with chemotherapy, radiation therapy, or targeted drugs for leukemia or lymphoma will often cause the spleen to shrink.
• For Hemolytic Anemias: Management of the specific anemia may reduce the workload on the spleen.

Splenectomy (Surgical Removal of the Spleen)

The surgical removal of the spleen is not performed simply because it is enlarged. A splenectomy is reserved for very specific situations, such as:

• In some cases of severe hemolytic anemia where the spleen is the primary site of red blood cell destruction.
• In some cases of lymphoma, for both diagnostic and therapeutic purposes.
• If the enlarged spleen is causing severe and dangerous symptoms from hypersplenism.
• In the rare event of a splenic rupture, which is a life-threatening emergency.

Removing the spleen leaves a person vulnerable to certain life-threatening infections for the rest of their life. Therefore, anyone undergoing a splenectomy must receive a series of crucial vaccinations before the surgery.

In most cases, treating the root cause naturally shrinks the spleen. But if the spleen starts “stealing” blood cells or causing pain, we sometimes have to step in more aggressively.

Splenomegaly, or an enlarged spleen, is not a disease but an important clinical sign of an underlying problem. It is a physical sign that the spleen is working overtime to fight an infection, is congested due to liver disease, or has been infiltrated by abnormal cells. The causes are vast, ranging from common infections like mononucleosis to serious conditions like cirrhosis and leukemia. An enlarged spleen should never be ignored. It is the starting point of a necessary medical investigation. Working with your doctor to uncover and treat the root cause is the key to managing the condition and protecting your overall health.

1. Mayo Clinic. (2022). Enlarged spleen (splenomegaly). Retrieved from https://www.mayoclinic.org/diseases-conditions/enlarged-spleen/symptoms-causes/syc-20354326
2. Cleveland Clinic. (2022). Enlarged Spleen (Splenomegaly). Retrieved from https://my.clevelandclinic.org/health/diseases/17231-enlarged-spleen-splenomegaly
3. American Society of Hematology (ASH). (n.d.). Splenectomy. Retrieved from https://www.hematology.org/education/patients/blood-disorders/spleen-and-splenectomy