Splenogonadal fusion

Last revised by Craig Hacking on 13 Oct 2022

Splenogonadal fusion is a rare anomaly that occurs when there is congenital fusion between a portion of the spleen and a gonad or other mesonephric derivative.

Much more common in male patients (~95%), occurs most commonly on the left (98%) and usually involve the testis (95%). Has been found in patients from birth to 81 years old.

Most often an incidental finding, but may present as a left-sided testicular mass or may present as cryptorchidism. The continuous type may be associated with other congenital anomalies, such as limb deformities or micrognathia.

The fusion of the two tissue types is assumed to occur between the 4th-10th weeks of gestation.

There are two main types 

  • continuous: gonad linked to spleen by a trans- or retroperitoneal cord of splenic tissue or fibrous cord with nodules of splenic tissue; often associated with other congenital anomalies
  • discontinuous: ectopic rests of splenic tissue are present in the gonad

Splenogonadal fusion with the ductus deferens or spermatic cord is exceedingly rare.

  • discontinuous form appears as a homogeneous, iso- to hypoechoic mass in the testis and is indistinguishable from a testicular malignancy
  • color Doppler may show a central feeding vessel that branches out toward the rest of the splenic tissue 
  • may show continuous or discontinuous relation between ectopic splenic tissue and gonad
  • if suspected prospectively, Tc99m-sulfur colloid may be used to identify ectopic splenic tissue in a gonad

Splenogonadal fusion is thought to have a benign prognosis, but is rarely diagnosed before orchiectomy.

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Cases and figures

  • Case 1: discontinuous type
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