Guy A. Bogaert
The testis is “undescended” if it is not in the scrotum or cannot be brought there during physical examination.
Cryptorchidism means hidden or obscure testis in Greek and is often used interchangeably with the term “undescended testis.” However, a cryptorchid testis may be atrophic or ectopic as opposed to truly undescended.
From a clinical point of view, the testis may be palpable or nonpalpable.
A. A testis which is not in the scrotum on physical examination is either palpable elsewhere or nonpalpable. A palpable testis may be found along the normal descending pathway (truly undescended, exiting the abdomen at the internal inguinal ring in the direction of the external inguinal ring), or ectopic outside the normal pathway (perineal, femoral, prepenile) (Fig. 3-1).
B. A testis outside the scrotum, but palpable, can be retractile (not truly undescended), incompletely descended (within the inguinal canal or just outside), or ectopic (following a different pathway, e.g., perineal, femoral).
C. The inability to palpate a testis (nonpalpable) means the testis is beneath the external oblique fascia (unusual), in the abdomen, or atrophic/absent.
A boy with a unilateral normal descended testis has the same paternity chance as a boy with bilateral normal descended testes (90%). Paternity rate in bilateral undescended testes is 62%.
The incidence of bilateral undescended testes is 5% to 15% of all boys with undescended testes.
A. A retractile testis is not truly undescended and is mostly palpated in the inguinal area. A retractile testis has an extrascrotal position intermittently because of an active cremasteric reflex. By definition, retractile testes function normally and do not require any form of treatment. In rare cases, a retractile testis can become “ascended,” and may eventually require treatment.
B. An ectopic testis (Fig. 3-1) (less than 5% incidence) descends properly until misdirected outside the external inguinal ring, presumably by an abnormal gubernaculum. These testes may be found in the perineum, prepenile, or femoral areas. These testes are thought to be more normal than incompletely descended testes.
C. An incompletely descended testis (Fig. 3-1) (95% incidence) can be intra-abdominal, in the inguinal canal, or just exiting the external ring (prescrotal).
FIG. 3-1 Patient’s left side depicts normal pathway for testicular descent illustrating possible locations of undescended testes. Patient’s right side shows possible locations of normal testes that descend into an ectopic position.
D. An absent or atrophic testis is uncommon (3.3% of all cryptorchid testes, likely the result of perinatal torsion).
A unilateral cryptorchid testis is among the most common congenital anomalies in boys and the most common surgical condition in pediatric urology.
A. The Undescended Palpable Testis
1. Newborns have an incidence of 3% to 5% of cryptorchidism (of those, 15% are bilateral).
2. Serial studies at 3 and 9 months of age have shown that most of these cryptorchid testes descend spontaneously.
3. By the age of 1 year, only 0.7% to 1% of these children will still have a cryptorchid testis (palpable along the expected descending pathway).
4. The same incidence of 0.7% has been found in young adults (military recruits), suggesting that no spontaneous descent occurs after 9 months of age.
B. The Nonpalpable Testis
1. In 20% of all children with a cryptorchid testis, the testis will be nonpalpable; however, only 25% of those will ultimately prove to be absent at surgical exploration.
2. In most cases (75% of all patients originally with a nonpalpable testis), a nonpalpable testis will be intra-abdominal, or depending on the experience of the examiner, in the inguinal canal.
C. Risk Factors for a Higher Incidence of an Undescended Testis
1. Newborn children who are premature, have a low birth weight, are small for gestational age, or twins have a significantly higher incidence of cryptorchidism.
2. Although it has been suggested that boys born after in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) would present more frequently with cryptorchidism, this has not been demonstrated in large epidemiologic studies.
D. The Ascending Testis
Boys, commonly aged 5 to 12 years of age, with a history of normal or retractile testis can present at this age with an “ascended” testis. These boys previously had a normal descended testis that has now become undescended. The etiology of the ascending testis is unknown but may be secondary to a large growth spurt or a persistent patent processus vaginalis. Ascended testes usually require surgical correction.
A. Until the 6th week of gestation, the gonads remain indifferent. During weeks 6 and 7, the effects of the testis determining factor (TDF) protein from the SRY gene (on the Y chromosome), result in differentiation into a testis. Also, in weeks 6 and 7, Sertoli cells develop and secrete müllerian inhibitory substance (MIS) that cause müllerian duct regression. From the 9th week of gestation, Leydig cells produce testosterone, which stimulates Wolffian duct development.
B. Testicular descent usually occurs in the third trimester (it has been documented by prenatal ultrasound that no descent is seen before 28 weeks gestation).
Many theories have been proposed to explain the etiology of cryptorchid testes.
A. Abnormality of the Gubernaculum Testis
1. The gubernaculum is a cordlike structure that extends from the lower pole of the epididymis and the testis to the scrotum.
2. It appears that the gubernaculum does not pull the testis into the scrotum but rather guides it by providing a space into which the testis can descend.
3. Absence or abnormality of the gubernaculum may be a cause of maldescent.
4. An ectopic testis is likely to be secondary to an abnormally positioned distal extension of the gubernaculum, leading the testis to an abnormal position.
B. Reduced Intra-abdominal Pressure
1. Overall, it is doubtful that diminished intra-abdominal pressure is an etiologic factor in most cases of cryptorchidism.
2. All patients born with the prune belly syndrome have intra-abdominal testes.
3. These may be due to reduced intra-abdominal pressure, but may also relate to a mass effect from bladder distension.
4. In a similar experiment of nature, patients with gastroschisis have a higher incidence of cryptorchidism.