A 6-month-old boy is brought to the urology clinic for follow-up of an undescended right testicle discovered during evaluation in the newborn nursery. Physical examination shows absence of a palpable right testis in the scrotal sac. However, a round mass is palpated superior to the scrotum in the inguinal canal. Orchiopexy, the placement and fixation of the testis in the scrotum, is recommended to the family. During this patient's procedure, the malpositioned testis will most likely be pulled through a physiologic opening in which of the following structures?
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Testicles develop in the fetal abdomen during organogenesis. Between 8 weeks and full term, each testis descends from the abdomen into the inguinal canal through the deep inguinal ring, which is an opening in the transversalis fascia (bounded laterally by the transversus abdominis muscle and medially by the inferior epigastric vessels). Each testis then passes anteromedially through the canal and enters the scrotum via the superficial inguinal ring, which is a physiologic opening in the external oblique aponeurosis above the pubic tubercle.
Cryptorchidism is the failure of one or both testes to descend into the scrotum before birth, which occurs more commonly in preterm neonates. An undescended testis usually descends spontaneously in the first few months of life. Testes that have not descended by age 6 months are unlikely to do so and require orchiopexy, or surgical fixation of the testis within the scrotum. In this case, the patient's undescended testicle is within the inguinal canal and must be mobilized through the superficial inguinal ring (ie, external oblique aponeurosis) and stitched into place in the base of the scrotum.
(Choices A and E) The conjoint tendon is the common tendon of the transversus abdominis and internal oblique muscles, and the transversalis fascia is the connective tissue membrane between the extraperitoneal fat and the transversus abdominis. These two structures form the posterior wall of the inguinal canal.
(Choice C) The femoral ring is a physiologic opening between the abdominal cavity and the femoral canal. It transmits lymphatic vessels but not the spermatic cord.
(Choice D) The rectus muscle sheath is formed by the confluence of the aponeuroses of the external and internal oblique muscles and the transversus abdominis muscle.
Educational objective:
The superficial inguinal ring is a physiologic opening in the external abdominal oblique aponeurosis, and surgical repair of an undescended testicle lodged in the inguinal canal involves moving the testis through the superficial inguinal ring and fixing it in the scrotum (ie, orchiopexy).