Asplenia means the absence of a spleen or a spleen that no longer works properly. This condition significantly increases the risk of severe infections, particularly from certain bacteria with protective outer coatings. While living without a spleen is possible with proper care, understanding the risks and taking preventive measures is essential for maintaining health and avoiding life-threatening complications.

Understanding What Asplenia Is

Asplenia refers to the situation where a person either does not have a spleen or has a spleen that does not function correctly. The spleen is a fist-sized organ located in the upper left side of the abdomen, tucked under the rib cage. Under normal circumstances, the spleen is not something you can feel when pressing on your belly, and it measures on average about 10.65 by 5.16 centimeters. Interestingly, the size of a healthy spleen can vary depending on factors such as sex and race. For example, men typically have larger spleens than women, and White individuals generally have larger spleens compared to African American individuals.^[1]

There are two main categories of asplenia. Anatomic asplenia means the spleen is physically absent from the body. This could be because someone was born without one or because it was surgically removed. Functional asplenia, on the other hand, means the spleen is present but has lost its ability to work properly. Various health conditions can damage the spleen to the point where it can no longer perform its important jobs, even though it remains in place.^[2]

How Common Is Asplenia

Congenital asplenia, which means being born without a spleen, is quite rare. The incidence is estimated to be up to 1 in 10,000 births. There are two distinct types of genetic disorders that can result in congenital asplenia: heterotaxy syndrome and isolated congenital asplenia.^[3] Worldwide, most people with asplenia or reduced spleen function actually have an underlying blood disorder called hemoglobinopathy, such as sickle cell disease, which causes the spleen to gradually lose its function.^[4]

The most common reason for anatomic asplenia in many countries is surgical removal of the spleen, called splenectomy. This procedure is most often performed following trauma that causes the spleen to rupture. Because the spleen stores blood cells, any serious injury to it can cause severe, uncontrolled bleeding that may require emergency surgery to remove the organ.^[5]

What Causes Asplenia

The causes of asplenia depend on whether it is anatomic or functional. When someone has anatomic asplenia, it means the spleen is completely absent. Some individuals are born without a spleen due to genetic changes, particularly variations in the RPSA gene, which is responsible for creating certain proteins. Sometimes congenital asplenia occurs as part of a rare syndrome called heterotaxy, which also affects other organs, usually the heart.^[2]

More commonly, anatomic asplenia results from surgical removal. The spleen may be removed following trauma or injury, such as a car accident or impact during contact sports that causes a ruptured spleen. Less frequently, doctors may recommend splenectomy to treat certain medical conditions. These include blood disorders like idiopathic thrombocytopenic purpura (a condition where the immune system destroys platelets), severe hemolytic anemias (where red blood cells are destroyed too quickly), or spherocytosis (an inherited condition affecting red blood cell shape).^[6]

The spleen may also be removed as part of cancer treatment. In some cases of lymphoma, an enlarged spleen causing pain or low blood cell counts may need to be removed. The spleen might also be removed during surgery for pancreatic cancer that starts in the part of the pancreas closest to the spleen.^[2]

Functional asplenia occurs when certain medical conditions damage the spleen, preventing it from working properly. Sickle cell disease is a leading cause of functional asplenia. In this blood disorder, abnormally shaped red blood cells block blood flow to the spleen, causing repeated damage through a process called autosplenectomy, where the spleen essentially destroys itself over time through multiple small injuries. Other conditions that can lead to functional asplenia include celiac disease, lupus, advanced HIV infection, and liver disease.^[2]

Risk Factors for Developing Complications

Anyone without a functioning spleen faces increased risk of serious infections, but certain groups are at particularly high risk. Children with asplenia are especially vulnerable because they often have lower levels of specific antibodies against bacteria with protective capsules. Young children’s immune systems are still developing, and the absence of a spleen makes it much harder for their bodies to fight these dangerous germs.^[4]

People whose immune systems are already compromised face additional dangers. Those with conditions that affect cellular immunity, such as Hodgkin’s disease or hypogammaglobulinemia (low levels of protective antibodies), have impaired ability to mount an effective antibody response. Similarly, patients undergoing chemotherapy or radiation therapy, and those who have had bone marrow transplantation, all have increased vulnerability to serious infections.^[12]

The timing of splenectomy also matters. Most serious infections occur within the first two years following spleen removal. However, this does not mean the danger passes after this period. People have developed serious infections more than forty years after a splenectomy, indicating that the increased risk persists throughout life.^[12]

Symptoms to Watch For

Asplenia itself typically does not cause any noticeable symptoms. The absence or dysfunction of the spleen operates silently in the background. What becomes critically important is recognizing the signs of infection, as these can quickly become dangerous for someone without a functioning spleen.^[2]

The most important symptom to watch for is fever. A temperature of 100.5 degrees Fahrenheit (38 degrees Celsius) or higher should be treated as a medical emergency in anyone with asplenia. Sometimes fever may be the only symptom initially, but this single sign requires immediate medical attention, ideally within one hour.^[14]

Other symptoms that may indicate a serious infection include chills and sweating, which often accompany fever. A person may experience dizziness or even pass out if the infection is affecting blood pressure. Digestive symptoms such as vomiting, diarrhea, or belly pain can signal that bacteria are spreading through the bloodstream. Respiratory symptoms like cough or trouble breathing may indicate pneumonia. Severe headache, neck pain, confusion, or seizures are concerning signs that could indicate meningitis, an infection of the membranes surrounding the brain and spinal cord.^[14]

The initial symptoms of a serious infection can be deceptively mild, often resembling influenza. A person might experience fever, general feeling of being unwell, muscle aches, headache, vomiting, diarrhea, and abdominal pain. However, the infection can then rapidly progress within hours to full-blown septic shock, accompanied by dangerously low blood pressure, kidney failure, widespread blood clotting problems, and low blood sugar.^[12]

Prevention Strategies

Because infections can be so dangerous for people with asplenia, prevention becomes absolutely critical. There are several key strategies that work together to protect against serious illness.

Vaccination is the cornerstone of prevention. Several vaccines are essential for people without functioning spleens. The pneumococcal vaccine protects against many types of bacteria that cause pneumonia and bloodstream infections. There are two types: the conjugate vaccine (PCV13 or PCV15) and the polysaccharide vaccine (PPSV23), and people with asplenia typically need both. The meningococcal vaccine protects against bacteria that cause meningitis and bloodstream infections. The Haemophilus influenzae type b (Hib) vaccine prevents serious infections from this bacterium, despite its misleading name which suggests it prevents flu. Annual influenza vaccination is also important, as is staying current with COVID-19 vaccines.^[6]

When spleen removal is planned in advance, vaccination should ideally be performed 14 days before surgery. This timing allows the immune system to develop protection while the spleen is still present to help create antibodies. If emergency splenectomy is necessary, vaccines should be given two weeks after surgery.^[6]

Preventive antibiotics play an important role, especially for certain groups. Daily antibiotic treatment with oral penicillin or amoxicillin should be considered for all children with asplenia until at least 5 years of age. Following splenectomy, children over 5 years old and adults should receive preventive antibiotics for at least one year. Some people with weakened immune systems or a history of serious infections may need to continue antibiotics for longer periods or even indefinitely.^[6]

Some doctors recommend that people with asplenia carry antibiotics with them at all times, often referred to as having “a pill in your pocket.” At the first sign of fever or other symptoms suggesting infection, these antibiotics can be started immediately while seeking urgent medical care.^[5]

Patient education is essential. People with asplenia should carry identification indicating their condition, such as a medical alert card, bracelet, or necklace. This alerts healthcare providers to the increased infection risk in emergency situations. They should inform all doctors and dentists about their condition. Precautions to avoid dog and tick bites are important, as these can introduce specific dangerous bacteria. Caution is recommended when traveling to areas where malaria is common, as people without spleens are at higher risk for severe malaria infection.^[6]

How the Body Changes Without a Spleen

The spleen performs several vital functions in the body, so understanding what happens when it is absent or not working helps explain why infections become so dangerous. The spleen has two functionally and structurally distinct parts: the white pulp and the red pulp. The white pulp contains a large mass of lymphoid tissue that produces antibodies against recognized germs. The red pulp has a tight network of small blood vessels called the cord of Billroth, which helps filter blood.^[1]

The spleen acts as the body’s largest blood filter. One of its main jobs is removing old or damaged red blood cells from circulation. It also harvests iron from old red blood cells for recycling into new ones. When needed, the spleen can even produce new red blood cells, though the bone marrow usually handles this task. Most importantly for understanding asplenia, the spleen contains special white blood cells called splenic macrophages that filter germs out of the blood. These macrophages are particularly important for defending against bacteria that have protective capsules around them.^[15]

When antibodies produced by the white pulp tag these capsulated bacteria, the splenic macrophages can then capture and kill them. Without a spleen, this crucial defense mechanism is lost, leaving the body vulnerable to rapid bacterial growth in the bloodstream.^[15]

Blood tests in people with asplenia show characteristic changes. A microscopic examination of blood often reveals Howell-Jolly bodies, which are small dark purple spots inside red blood cells representing leftover fragments of genetic material. In people with functioning spleens, these are normally removed as blood filters through the organ. Their presence on a blood smear is often the first clue that someone has asplenia or reduced spleen function. Other blood changes include increased numbers of certain white blood cells (lymphocytosis and neutrophilia), increased platelet counts (reactive thrombocytosis), and the appearance of target cells (red blood cells with a distinctive appearance).^[6]

The immune system also undergoes changes. There is decreased production of certain immunoglobulins (IgG and IgM), which are antibody proteins crucial for fighting infection. This leads to decreased activation of the complement system, a group of proteins that help antibodies and immune cells clear bacteria from the body. Specifically, there is reduced opsonization, the process of coating bacteria with proteins to make them easier for immune cells to recognize and destroy.^[6]

People with asplenia also lack IgM memory B cells, a specific type of immune cell that “remembers” previous encounters with germs and responds quickly to repeat infections. This deficiency, combined with poor response to polysaccharide vaccines (which protect against capsulated bacteria), explains much of the increased infection risk. The spleen normally contains specialized cells that respond to these vaccines, so without a functioning spleen, protection is limited.^[3]

The most dangerous complication is overwhelming post-splenectomy infection (OPSI), also called asplenic sepsis. This is a bacterial infection that rapidly progresses to fulminant, overwhelming blood infection. The most common culprits are encapsulated bacteria, particularly Streptococcus pneumoniae (which causes pneumococcal pneumonia), Neisseria meningitidis (which causes meningococcal disease), and Haemophilus influenzae. In OPSI, bacterial growth can be so extreme that bacteria are visible in blood samples examined under a microscope.^[6]

Without treatment, the mortality rate from OPSI is approximately 70 percent. Even with early treatment, mortality can range from 10 to 40 percent. More than half of patients who die do so within 48 hours of hospital admission, demonstrating how rapidly these infections can progress. This is why immediate antibiotic treatment at the first sign of fever is so critical.^[6]