The spleen helps prevent infection by supporting efficient function of the immune system. This small organ is found above the stomach on the left side of the rib cage, but small nodules can also form in other areas. These nodules are known as supernumerary or accessory spleens, and they can occasionally cause health issues in some individuals.
Accessory spleens may result from abnormalities during foetal development that prevent cells from properly attaching to the mass of the spleen. Supernumerary spleens can also develop after a splenectomy with some autoimmune conditions, such as immune thrombocytopenia.
In some cases, a condition called splenosis can cause splenic tissue to migrate to other areas. However, this condition is separate from supernumerary spleen because it results from surgery or abdominal injury.
In the majority of cases, accessory spleens cause no symptoms. In fact, a person may not even be aware of the issue until diagnostic imaging confirms the presence of misplaced splenic tissue. When symptoms do occur, they typically include pain and discomfort in the abdomen. Because these symptoms can occur with more serious conditions, it’s important to have them assessed as soon as possible.
Treatment is only necessary when a person experiences health effects related to a supernumerary spleen. Accessory spleens can also rupture or become twisted, in which case treatment may be required. When there’s a chance of more serious effects, doctors can perform a resectioning procedure to attach splenic nodules to the spleen itself. In the event accessory spleens develop after a splenectomy, doctors will likely recommend removal of the nodules.