What is the Spleen?

The spleen is one of the abdominal organs, found above the stomach on the left side of the body. Historically, many people thought the spleen was of limited purpose, and it was a common target for prophylactic removal in surgeries where the abdomen was already open, on the logic that taking it out would prevent disease in the future. Research now shows that this organ actually plays an important role in a number of bodily functions, and a splenectomy can be dangerous for a patient unless it appears to be medically indicated.

This organ is made up of mottled white and red tissue. Blood and lymph move through the spleen so it can break down old components, retain useful products for recycling, and discard the rest. This organ plays a role in the circulation of both lymph and blood and is important for immune function. People without spleens are more likely to experience severe infections like pneumonia and have an increased mortality risk.

During fetal development, the spleen makes red blood cells. The bone marrow will eventually take over, but this organ still plays a role in regulating the number of blood cells in circulation. It recycles red blood cells and captures their iron for the body to use, and also maintains a reserve of blood. When people lose a lot of blood, the spleen can release the extra blood to prevent shock; in a way, this organ is the body's own unit of blood for transfusion, although the spleen cannot prevent patients with severe injuries from going into shock.

With lymphatic circulation, this organ sequesters infectious materials and scraps of old cells for disposal to keep the immune system in good working order. It also retains a store of immune cells it can release in response to major inflammation or infection. If the immune system is depressed, the spleen may take action as backup in an attempt to fight disease. Patients who lack this fail-safe are at increased risk when they have serious diseases.

Patients can experience problems with the spleen, often leading to splenomegaly, where the organ enlarges in response to infection, problems with blood cells, or cancer. Doctors can use blood tests and medical imaging to explore the causes of the problem and determine if a splenectomy is necessary. They may wait and see if conservative treatment works before taking the organ out, with the goal of protecting the patient's future immune health.