Splenogonadal fusion is a rare congenital malformation that results from an abnormal connection between the primitive spleen and gonad during gestation. A portion of the splenic tissue then descends with the gonad. Splenogonadal fusion has been classified into two types: continuous, where there remains a connection between the main spleen and gonad; and discontinuous, where ectopic splenic tissue is attached to the gonad, but there is no connection to the orthotopic spleen. Patients can also have an accessory spleen. Patients with continuous splenogonadal fusion frequently have additional congenital abnormalities including limb defects, micrognathia, skull anomalies, Spina bifida, cardiac defects, anorectal abnormalities, and most commonly cryptorchidism. Terminal limb defects have been documented in at least 25 cases which makes up a separate diagnosis of splenogonadal fusion limb defect (SGFLD) syndrome. The anomaly was first described in 1883 by Bostroem. Since then more than 150 cases of splenogonadal fusion have been documented, predominantly in males. The condition is considered benign. A few cases of testicular neoplasm have been reported in association with splenogonadal fusion. The reported cases have occurred in patients with a history of cryptorchidism, which is associated with an elevated risk of neoplasm. Splenogonadal fusion occurs with a male-to-female ratio of 16:1, and is seen nearly exclusively on the left side. The condition remains a diagnostic challenge, but preoperative consideration of the diagnosis and use of ultrasound may help avoid unnecessary orchiectomy. The presence of splenic tissue may be confirmed with a technetium-99m sulfur colloid scan. Classification Splenogonadal fusion is separated into two types: Continuous (55%): The native spleen is connected to the gonad. The connection occurs through a cord of splenic tissue or fibrous band. Discontinuous (45%): Ectopic splenic tissue is present and attached to the gonad. An accessory spleen is present and the native spleen lacks the direct attachment to the gonad. Pathogenesis The cause of splenogonadal fusion is still unclear, and there are several proposed mechanisms. A developmental field defect that occurs during blastogenesis is the current explanation of pathogenesis. The spleen derives from mesenchymal tissue and an inappropriate fusion can happen between the gonadal ridge during gut rotation, which occurs between weeks 5 and 8 of fetal life. Splenogonadal fusion may result from an unknown teratogenic insult. The timing of this insult may correlate to the severity of associated defects. There is also postulation that fusion may occur due to adhesion after an inflammatory response or