Patency of the "third inguinal ring" in children with unilateral cryptorchidism: fact or fiction?

The entrance to the scrotum, or the so-called "third inguinal ring" (3rd IGR), was thought to be an important finding and etiological factor for cryptorchidism at the beginning of the 20th century. Historical reports of its association with undescended testis suggest that it was considered by many to be a true anatomical entity. As the understanding of testicular descent has changed, the description of this anatomical passage has vanished from textbooks and publications. In order to evaluate the findings that led to its original report, we sought to assess the patency of the expected testicular path of descent into the scrotum in children with unilateral cryptorchidism.

Two hundred consecutive children who underwent unilateral orchidopexy were prospectively evaluated at the time of surgery to determine the anatomical patency of the area thought to represent the 3rd IGR. We also evaluated its association with the patient's age at surgery, the affected side, position of the undescended testis, macroscopic epididymal anomalies (MEA), and the patency of the processus vaginalis (PV).

The mean age at surgery was 5.2 +/- 3.0 years, ranging from 1 to 13 years. The 3rd IGR was closed in 118 boys (59.0 %) and open in 82 (41.0 %). A closed 3rd IGR was found significantly more frequently in patients with intra-abdominal testes (p < 0.01). No significant association was observed between patency of the 3rd IGR and other evaluated factors.

Our results suggest that the so-called 3rd IGR may represent the passage point of the testicle into the scrotum, which was not patent during the intraoperative examination in (2/3) of children with unilateral cryptorchidism. This observation by surgeons at the beginning of the 20th century may represent an anatomical curiosity rather than an important factor in the pathogenesis of cryptorchidism.