accessory spleen/Splenule

he spleen can present with a wide range of anomalies involving its shape, location, number, and size. An accessory spleen is one such anomaly. Also called supernumerary spleen, splenule, ora splenunculus, the accessory spleen is a congenital defect in which ectopic splenic tissue is found separated from the body of the actual spleen. It is a common benign condition found in more than 10% of the population.In most cases, individuals affected by the condition have one splenule; however, as many as six accessory splenic buds have been reported in one patient.The most common location for a splenule is near the splenic hilum; however, it can be found anywhere in the abdomen and even in the pelvis and scrotum. Typical splenule appears as a solid mass, approximately 1 to 3 cm in diameter, with a smooth, round, or ovoid shape and well-defined fibrotic capsule. Microscopically, it is identical to the actual spleen. SPLEEN SAG176

 

 

Splenule is commonly accepted as a congenital defect that develops due to the failure of cell fusion during embryonic development. It is often confused with splenosis, which is another form of ectopic splenic tissue. In contrast to accessory spleen, splenosis is an acquired condition caused by a trauma that results in a part of the spleen breaking off and embedding itself somewhere else in the abdominal cavity. The newly embedded ectopic splenic tissue becomes functional by recruiting local blood supply. An accessory spleen and splenosis are functionally and histologically similar to normal splenic tissue. However, splenosis is missing key splenic characteristics such as a thick capsule and a blood supply arising from the splenic artery

 

An accessory spleen is usually asymptomatic and discovered incidentally on imaging tests performed for unrelated issues. The condition, however, becomes clinically significant in three scenarios. First, the accessory spleen can undergo compensatory hypertrophy after splenectomy performed due to various hematological disorders. In such cases, splenule can cause the recurrence of the disorder for which the spleen removal has been performed. Thus, all accessory spleens should be removed during splenectomy when the intention is to remove all functional splenic tissue. SPLEEN SAGRound soft tissue structure in the splenic hilum area is an incidentally found accessory spleen.177

 

 

Conversely, in patients with splenic trauma, an accessory spleen may become clinically important to preserve splenic function in the case of splenectomy. Second, during medical imaging, an accessory spleen may be confused with an enlarged lymph node or tumor in the tail of the pancreas, gastrointestinal tract, kidney, adrenal gland, or gonads.Third, an accessory spleen may occasionally become symptomatic because of torsion, spontaneous rupture, hemorrhage, or cyst formation, and can cause an acute abdomen.On ultrasound, splenules are typically round or oval well-demarcated soft tissue structures isoechoic to spleen measuring 1 to 3 cm. They are most often found near the spleen’s hilum or near the tail of the pancreas. On CT, splenules have density and enhancing characteristics similar to the rest of thespleen. Conversely, if a mass is seen at the splenic hilum and does not enhance in the same fashion as the adjacent spleen, then alternative diagnoses should be entertained. Although ultrasonography, CT, and MRI are essential in identifying and evaluating accessory spleens, a definitive diagnosis via imaging relies on nuclear medicine.194-201SPLENULE TRVSPLENULE SAGRound soft tissue structure isoechoic to spleen is an incidentally found splenule.178