Undescended Testicle

Although it has been known since ancient times that the testicles originated in the abdomen before migrating to the scrotum, John Hunter in the 1750s was one of the first to dissect human fetuses to analyze this process.
Hunter named the structure attached to the fetal testes the “gubernaculum” (rudder), as he believed it was responsible for mediating testicular descent.¹
Until the 19th century, undescended testicles (UDTs) were generally treated with castration.
James Adams attempted the first surgical correction of a UDT in 1871 at the London Hospital. He was successful, but the patient died on postoperative day 3 of a wound infection. Thomas Annandale performed the first successful orchiopexy 6 years later.
In 1916, Daniel Eisendrath suggested at the American Urological Society that surgical correction be performed in all patients within the first 2 years of life.²

RELEVANT ANATOMY

In utero, the testes form from the gonadal ridges in the abdomen.
The testes travel to the scrotum through the inguinal canal during normal development from an unclear mechanism, possibly mediated by the developing gubernaculum, a structure that attaches to the fetal testes (Figure 43.1).
Normally, the testes migrate through the inguinal canal at week 28 and are located in the scrotum by week 33.³
The inguinal canal carries the spermatic cord and the ilioinguinal nerve from the abdomen to the scrotum (Figure 43.2).
The spermatic cord contains the genital branch of the genitofemoral nerve, vas deferens, pampiniform plexus, lymphatics, and arteries.
The deep ring of the inguinal canal is through the transversalis fascia; the superficial ring is through the aponeurosis of the external oblique muscle.

Figure 43.1 The process of testicular descent. A, The testicles originate from the posterior abdomen and begin to descend around 2 months. B, The testicles arrive in the scrotum before birth via a patent processus vaginalis. C, After birth, the processus vaginalis becomes obliterated. (Reprinted with permission from Lawrence PF, Bell RM, Dayton MT, Herbert JC. Essentials of General Surgery. 5th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2012).

EPIDEMIOLOGY AND ETIOLOGY

Incidence: Up to 30% of preterm and 3% of full-term infants are born with an undescended testis, but descent usually completes within the first few weeks of like. The incidence at 9 months is <1%.⁴

Etiology: Multifactorial but anatomic and hormonal factors have been implicated. The gubernaculum, which connects the inferior pole of the testis to the scrotum, is thought to guide the descent from the retroperitoneum to the scrotum. Hormonal factors, including insulinlike factor 3 and testosterone, are involved in initiating the descent.⁵

Decreased intra-abdominal pressure due to congenital wall defects (floppy belly syndrome, gastroschisis, omphalocele) has been implicated as well.⁶

CLINICAL PRESENTATION

Classic presentation: an otherwise healthy baby who presents with a nonpalpable testis.

It is paramount to distinguish this from retractile testis, which is a variant of normal anatomy where a hyperactive cremaster

muscle pulls the testis superiorly, through the external inguinal ring into the inguinal canal. Unlike UDTs, the testis can be permanently manipulated back into the scrotum.
The classic physical examination finding in UDT is an empty hemiscrotum.⁷

Figure 43.2 Inguinal canal anatomy. A, Anterior view. B, Schematic sagittal section of inguinal canal. (Reprinted with permission from Moore K, Dalley A, Agur A. Clinically Oriented Anatomy. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:204).

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