Epidemiology

An undescended (cryptorchid) testis is the most common disorder of sexual differentiation in boys. At birth, approximately 4.5% of boys have an undescended testis. Because testicular descent occurs at 7-8 mo of gestation, 30% of premature male infants have an undescended testis; the incidence is 3.4% at term. The majority of congenital undescended testes descend spontaneously during the first 3 mo of life, and by 6 mo the incidence decreases to 0.8%. If the testis has not descended by 4 mo, it will remain undescended. Cryptorchidism is bilateral in 10% of cases. There is some evidence that the incidence of cryptorchidism is increasing. Although cryptorchidism usually is considered to be congenital, an undescended testis is being diagnosed in an increasing number of older boys. Typically these boys have a scrotal testis that “ascends” to a low inguinal position, and therefore require an orchiopexy. Some boys have secondary cryptorchidism after repair of an inguinal hernia. This complication is most common in neonates and young infants and affects as many as 1-2% of patients undergoing hernia repair.

Pathogenesis

The process of testicular descent is regulated by an interaction between hormonal and mechanical factors, including testosterone, dihydrotestosterone, müllerian-inhibiting factor, the gubernaculum, intra-abdominal pressure, and the genitofemoral nerve. The testis develops at 7-8 wk of gestation. At 10-11 wk, the Leydig cells produce testosterone, which stimulates differentiation of the wolffian (mesonephric) duct into the epididymis, vas deferens, seminal vesicle, and ejaculatory duct. At 32-36 wk, the testis, which is anchored at the internal inguinal ring by the gubernaculum, begins its process of descent. The gubernaculum distends the inguinal canal and guides the testis into the scrotum. Following testicular descent, the patent processus vaginalis (hernia sac) normally involutes. A small percentage have Klinefelter syndrome or mutations in the insulin-like factor 3 receptor.

Clinical Manifestations

Undescended testes can be classified as abdominal (nonpalpable), peeping (abdominal but can be pushed into the upper part of the inguinal canal), inguinal, gliding (can be pushed into the scrotum but retracts immediately to the pubic tubercle), and ectopic (superficial inguinal pouch or, rarely, perineal). Most undescended testes are palpable just distal to the inguinal canal over the pubic tubercle.

A disorder of sexual development (DSD; aka intersex) should be suspected in a newborn phenotypic male with bilateral nonpalpable testes, as the child could be a virilized girl with congenital adrenal hyperplasia (Chapter 570). In a boy with midpenile or proximal hypospadias and a palpable undescended testis, DSD is present in 15%, and the risk is 50% if the testis is nonpalpable.

The consequences of cryptorchidism include infertility, testicular malignancy, associated hernia, torsion of the cryptorchid testis, and the possible psychologic effects of an empty scrotum.

The undescended testis is normal at birth histologically, but pathologic changes can be demonstrated by 6-12 mo. Delayed germ cell maturation, reduction in germ cell number, hyalinization of the seminiferous tubules, and reduced Leydig cell number are typical; these changes are progressive over time if the testis remains undescended. Similar, although less severe, changes are found in the contralateral descended testis after 4-7 yr. After treatment for a unilateral undescended testis, 85% of patients are fertile, which is slightly less than the 90% rate of fertility in an unselected population of men. In contrast, following bilateral orchiopexy, only 50-65% of patients are fertile.

The risk of a germ cell malignancy (Chapter 497) developing in an undescended testis is 2-4 times higher than that in the general population and is approximately 1/80 with a unilateral undescended testis and 1/40-50 for bilateral undescended testes. Testicular tumors are less common if the orchiopexy is performed before 10 yr of age, but they still occur, and adolescents should be instructed in testicular self-examination. The peak age for developing a testis tumor is 15-45 yr. The most common tumor developing in an undescended testis in an adolescent or adult is a seminoma (65%); after orchiopexy, seminomas represent only 30% of testis tumors. Orchiopexy seems to reduce the risk of seminoma. Whether early orchiopexy reduces the risk of developing cancer of the testis is controversial, but it is uncommon for testis tumors to occur after orchiopexy performed before the age of 2 yr. The contralateral scrotal testis is not at increased risk for malignancy.

An indirect inguinal hernia usually accompanies a congenital undescended testis but rarely is symptomatic. Torsion and infarction of the cryptorchid testis also are uncommon but can occur because of excessive mobility of undescended testes. Consequently, inguinal pain and/or swelling in a boy with an undescended testis should raise the suspicion of an incarcerated hernia or testicular torsion of the undescended testis.

“Acquired” or ascending undescended testes occurs when a boy has a descended testis at birth, but during childhood, usually between 4-10 yr of age, the testis does not remain in the scrotum. Such boys often have a history of a retractile testis. With testicular ascent, on physical examination the testis often can be manipulated into the scrotum, but there is obvious tension on the spermatic cord. This condition is speculated to result from incomplete involution of the processus vaginalis, restricting spermatic cord growth, resulting in the testis gradually moving out of its scrotal position.

Retractile testes may be misdiagnosed as undescended testes. Boys >1 yr often have a brisk cremasteric reflex, and if the child is anxious or ticklish during scrotal examination, the testis may be difficult to manipulate into the scrotum. Boys should be examined with their legs in a relaxed frog-leg position, and if the testis can be manipulated into the scrotum comfortably, it is probably retractile. It should be monitored every 6-12 mo with follow-up physical examinations, because it can become an acquired undescended testis. Overall, as many as one third of boys with a retractile testis develop an acquired undescended testis, and boys <7 yr of age at diagnosis of a retractile testis are at greatest risk. Most think that boys with a retractile testis are not at increased risk for infertility or malignancy.

A nonpalpable testis accounts for 10% of undescended testes. Of these, 50% are viable testes in the abdomen or high in the inguinal canal, and 50% are atrophic or absent, almost always in the scrotum, secondary to spermatic cord torsion in utero (vanishing testis). If the nonpalpable testis is abdominal, it will not descend after 3 mo of age. Although sonography often is performed to try to identify whether the testis is present, it rarely changes clinical management, because the abdominal testis and atrophic testis are not identified on sonography. CT scanning is relatively accurate in demonstrating the presence of the testis. MRI is even more accurate, but the disadvantage is that general anesthesia is necessary in most young children. Because imaging has not been proved to be 100% reliable in demonstrating whether the testis is present or absent, its routine use is discouraged.

On physical examination of the scrotum, the child should be entirely undressed, to help him relax. If the testis is nonpalpable, the “soap test” often is useful; soap is applied to the inguinal canal and the examiner’s hand, significantly reducing friction and facilitating identification of an inguinal testis. In addition, pulling on the scrotum might make an inguinal testis palpable. One soft sign that a testis is absent is contralateral testicular hypertrophy, but this finding is not 100% diagnostic.

Treatment

The congenital undescended testis should be treated surgically no later than 9-15 mo of age. With anesthesia by a pediatric anesthesiologist, surgical correction at 6 mo is appropriate, because spontaneous descent of the testis will not occur after 4 mo of age. Most testes can be brought down to the scrotum with an orchiopexy, which involves an inguinal incision, mobilization of the testis and spermatic cord, and correction of the indirect inguinal hernia. The procedure is typically performed on an outpatient basis and has a success rate of 98%. In some boys with a testis that is close to the scrotum, a prescrotal orchiopexy can be performed. In this procedure, the entire operation is performed through an incision along the edge of the scrotum. Often the associated inguinal hernia also can be corrected with this incision. Advantages of this approach over the inguinal approach include shorter operative time and less postoperative discomfort.

Hormonal treatment is used infrequently. The theory is that because testicular descent is under androgenic regulation, human chorionic gonadotropin (HCG, which stimulates Leydig cell production of testosterone) or luteinizing hormone–releasing hormone (LHRH) may stimulate testicular descent. Although hormonal treatment has been used in Europe, randomized controlled trials have not shown either of these hormonal preparations to be effective in stimulating testicular descent. There has been some preliminary evidence that an LHRH analog, buserelin, may be helpful in increasing germ cell number and normalizing testicular histologic features.

In boys with a nonpalpable testis, diagnostic laparoscopy is performed in most centers. This procedure allows safe and rapid assessment of whether the testis is intra-abdominal. In most cases, orchiopexy of the intra-abdominal testis located immediately inside the internal inguinal ring is successful, but orchiectomy should be considered in more difficult cases or when the testis appears to be atrophic. A 2-stage orchiopexy sometimes is needed in boys with a high abdominal testis. Boys with abdominal testes are managed with laparoscopic techniques at many institutions. Testicular prostheses are available for older children and adolescents when the absence of the gonad in the scrotum might have an undesirable psychologic effect. The U.S. Food and Drug Administration (FDA) has approved a saline testicular implant. Solid silicone “carving block” implants also are used (Fig. 539-1). Placement of testicular prostheses early in childhood is recommended for boys with anorchia (absence of both testes).

Figure 539-1 A, Adolescent with solitary left testis. B, Appearance following implantation of right testicular prosthesis.