Splenules

Splenules, also known as accessory spleens, are small nodules of normal splenic tissue that exist separately from the main spleen. They arise during embryonic development when part of the splenic tissue fails to fuse with the developing spleen.

Most splenules are located near the spleen itself, typically at the splenic hilum. They can also be found in other locations such as the tail of the pancreas, the greater omentum, or the mesentery. Sizes are usually 1 to 2 centimeters but may be larger in some cases. Each splenule contains normal splenic tissue, including red and white pulp, and receives arterial supply from branches of the splenic artery or nearby vessels depending on its location.

Clinical significance is generally limited. Splenules are often discovered incidentally on imaging or during surgery and are usually asymptomatic. They can be mistaken for lymph nodes or neoplasms on radiographs. In patients undergoing splenectomy for hematologic or other conditions, the presence of accessory spleens can allow continued splenic function and persistence of disease symptoms; therefore, clinicians may consider removing accessory spleens to ensure complete treatment in certain scenarios.

Diagnosis is commonly achieved through imaging. Ultrasound, CT, or MRI can identify nodules with imaging characteristics similar to the spleen. Nuclear medicine studies using technetium-99m-labeled red blood cells or sulfur colloid can confirm splenic tissue by showing uptake in the splenule.

Management is typically conservative. No treatment is needed for incidental, asymptomatic splenules. Intervention may be considered if there is diagnostic uncertainty, or to prevent persistence of disease after splenectomy.