Causes and treatments for undescended testes
Professor Amulya Saxena (MD, PhD) is a Consultant Paediatric Surgeon at Chelsea and Westminster Hospital (NHS) and Bupa Cromwell Hospital.
Undescended testes (Cryptorchidsm) is the most common genital pathology encountered in paediatrics, affecting approximately 3% of full-term male newborns, and 1% of male infants aged six months to one year. The prevalence of undescended testes is as high as 30% in boys born prematurely, and spontaneous descent after the child’s first year is uncommon.
If left untreated this condition can have harmful effects on the testes over time, so early referral to a paediatric surgeon is warranted in newborns and infants once a diagnosis of non-palpable testes has been established.
Normal testicular descent
Normal testicular development begins at conception and is determined by the SRY gene. At the 3rd-5th gestational weeks, the gonadal ridge develops in the foetus. This is followed by Sertoli cells secreting a substance to cause the regression of Müllerian ducts (which in females go on to form the fallopian tubes, uterus and cervix). Leydig cells also develop and secrete testosterone. Testicular descent takes place in the 28th-40th gestational week via trans-inguinal migration, which is under hormonal control and results in a scrotal testis by the end of gestation.
What causes undescended testes?
There are a number of factors, and birth weight is the most significant in boys from birth to one year old. Trans-abdominal descent of the testes involves differential growth of vertebrae and the pelvis until the 23rd gestational week, after which further descent is facilitated by the development of a foetal ligament (the gubernaculum - which connects the testis and epididymis to the bottom of the scrotum), spermatic vessels, and scrotum. A normal hypothalamic-pituitary-gonadal (HPG) axis is a precondition for testicular descent, and the conversion of testosterone to dihydrotestosterone (DHT) is necessary for continued migration.
The development of the gubernaculum is particularly important as this is not firmly attached to the scrotum in patients with undescended testes. Intra-abdominal pressure also plays a role in testicular descent, and conditions associated with decreased pressure, such as Prune belly syndrome, cloacal exstrophy (a birth defect where abdominal organs are exposed), and gastroschisis (where the abdominal contents protrude through the abdominal wall) are associated with an increased risk of undescended testes.
The most useful determination is whether the testes are palpable on examination. Physique, testicular position, and compliance of the child could all influence proper localisation of an undescended testis. Approximately 80% of undescended testes are palpable and 20% are nonpalpable. Non-palpable testes may be intra-abdominal or absent. Palpable testes may be undescended, ectopic, or retractile (figure 1).
Ectopic testes exit the superficial inguinal ring and are then misdirected along the normal course of the testis. Retractile testes may be palpated anywhere along the natural course of the testis, although most are inguinal. These may be located just above the scrotum however, and if there is an active cremasteric reflex (where lightly stroking the inner thigh causes contraction of the muscle that pulls up the testis), they can be manipulated into the scrotum. There is a c.50% risk of subsequent ascent however, and children with retractile testes should be regularly monitored, at least until puberty.
Figure 1: Localisation of undescended testes and ectopic testes
Surgical treatment should be offered for infants between six months and one year old with undescended testes. Successful surgical placement of the testis in the scrotum requires adequate mobilisation of the testis and spermatic vessels, ligation of the associated hernia sac, and fixation of the testis in a dependent portion of the scrotum. However, different surgical techniques are required based on the location (inguinal, abdominal or ectopic) and the size of the testes (normal or atrophic).
Surgery for palpable undescended testes
In most boys with palpable inguinal undescended testes, a one-step orchidopexy is sufficient. This is the procedure to move an undescended testicle into the scrotum and permanently fix it there. However, if there is insufficient length the Prentiss manoeuver is used, where the internal inguinal ring is opened to help move the testes into the scrotum.
In rare cases, a two stage orchidopexy is performed when the Prentiss manoeuver and cord dissections have failed to gain adequate length. In these patients, the testis is anchored in its most dependent position, and a second operation is performed 6-12 months later to bring the testes into the scrotum.
Figure 2: Laparoscopic view of right undescended testes
Surgery for non-palpable testes
If a testis is not located in the inguinal area during physical examination, diagnostic laparoscopy is used to explore for a non-palpable testis, and the following are likely to be encountered:
1. blind-ending spermatic vessels above the internal inguinal ring
2. intra-abdominal testis (figure 2)
3. cord structures (vessels and vas deferens) that enter the internal ring
Blind-ending vessels point to a vanishing testis syndrome, probably due to prenatal vascular damage. A blind-ending vas deferens or absent spermatic vessels warrant further exploration, and if testicular remnants are found then removal may be possible with laparoscopic dissection or inguinal incision. If a testicular nubbin is found within the inguinal ring, scrotum or even abdomen, they can be resected and secured to prevent possible future torsion.
If the testis is intra-abdominal and farther from the internal ring, the 2-stage Fowler-Stephens orchidopexy is the preferred procedure. In the first stage, the internal spermatic artery is divided, allowing the testis to survive on the blood supply of the vas deferens and the cremasteric attachments. The second stage, performed 6-12 months later, then involves moving the testes from the abdomen to scrotum.
Outcomes and follow-up
Based on the location of the undescended testes, a success rate of 92% has been found for those located beyond the external ring, 82% for peeping testes, (located around the superficial inguinal ring), 87% for canalicular testes (located within the inguinal canal), and 74% for abdominal testes. Surgical success rates are 89% for inguinal orchidopexy, 81% for trans-abdominal orchidopexy and 77% for the 2-stage Fowler-Stephens orchidopexy.
Treatment should not end with the first postoperative follow-up. The child should be evaluated at 2-3 weeks and again at 6-12 months following surgery to determine testis location, size and viability. When the child reaches puberty, the doctor should advise of potential issues of fertility and testicular cancer, and give information about a monthly testicular self-examination.
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