An accessory spleen is a small, extra piece of spleen tissue that is usually found near the main spleen. Most people who have one never know about it.
What exactly is an accessory spleen?
The spleen does important jobs in the body. It filters the blood, breaks down old blood cells, and helps the immune system. In some people, during development in the womb, more than one piece of spleen tissue forms. These extra pieces are called accessory spleens. They are quite common. About one in ten people has at least one. They are usually only a few millimetres across, though rarely they can grow to a few centimetres. They are most often found close to the main spleen, but sometimes they sit elsewhere in the abdomen.
How does an accessory spleen form?
In the womb, the spleen begins to grow from several small clusters of tissue. Normally, these all join together to form one single organ. Sometimes, a small piece stays separate and continues to grow on its own. This becomes an accessory spleen. It is not a disease or a problem. It is simply a normal variation in the way the body is built.
Where are accessory spleens found, and how are they discovered?
Accessory spleens are most often found right at the edge of the main spleen or very close to it. They can also appear near the pancreas, along the large blood vessels in the abdomen, or in the connective tissue of the abdominal cavity. They almost never cause any symptoms and are usually found by chance, for example during an ultrasound scan, a CT scan, or an operation in the abdomen. They often only come to light when a doctor is looking carefully for changes in the abdomen, such as when investigating unexplained pain or checking for tumours.
Does an accessory spleen need treatment?
In the vast majority of cases, an accessory spleen is harmless and needs no treatment. It does not usually cause any symptoms and goes unnoticed throughout a person's life. Even when one is found, there is generally no cause for concern. Only very rarely can an accessory spleen cause problems, for example if it grows unusually large or becomes twisted. This is extremely uncommon. If the main spleen needs to be removed for medical reasons, such as due to a disease, it may make sense to remove any accessory spleens at the same time. This is because they could otherwise take over some of the spleen's functions. However, this is always an individual decision and is discussed in the context of the underlying condition.
Is an accessory spleen different from the normal spleen?
An accessory spleen is made of the same tissue as the main spleen and carries out the same tasks, just on a much smaller scale. This means it also contributes to the immune defence and breaks down old blood cells, but its share of these tasks is very small compared to the main spleen.
What does the finding "accessory spleen" mean in a medical letter?
If a medical letter or report mentions an accessory spleen, it is almost always an incidental finding with no medical significance. It is simply an anatomical variation that has no effect on health. No treatment or monitoring is usually needed. Only when a complete removal of all spleen-like tissue is required for certain spleen conditions does the presence of an accessory spleen become relevant.
When is an accessory spleen medically important?
An accessory spleen becomes important mainly when the main spleen needs to be removed for medical reasons, for example in certain blood disorders. In these cases, an accessory spleen can mean that the symptoms of the underlying condition do not fully go away, because the extra tissue continues to carry out its function. Before a planned spleen removal, doctors sometimes look specifically for accessory spleens to make sure none are left behind that could affect the treatment.
In summary: no need to worry about an accessory spleen
An accessory spleen is a common and harmless anatomical variation. It usually goes unnoticed and only very rarely causes any symptoms. If one is found by chance, there is generally no reason for concern or for any further action.
