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1. What are the main embryological features of the testis?
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The testis arises from the mesodermal germinal ridge in the posterior wall of the abdominal cavity. It links up with the epididymis and vas deferens, which develop from the mesonephric duct. As the testis enlarges, it undergoes caudal migration. By the third month of fetal life it is in the iliac fossa; by the seventh month it reaches the inguinal canal; by the eighth month it has reached the external inguinal ring; and by the ninth month, at birth, it has descended into the scrotum. During this descent, a prolongation of peritoneum, called the processus vaginalis, projects into the fetal scrotum; the testis slides behind this and is thus covered in front and sides by peritoneum. The processus vaginalis becomes obliterated at about the time of birth, leaving the testis covered by the tunica vaginalis. As expected from the embryology, abnormalities of descent are more common in premature infants than in full-term infants (2%).
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2. What happens to the processus vaginalis at the time of birth?
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In the term infant this becomes obliterated to form the tunica vaginalis.
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3. What is the incidence of abnormalities of descent of testis in the full-term infant?
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Approximately 2%
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4. What are the main two types of maldescent of the testis?
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Testicular maldescent can be subdivided according to whether or not the testis followed the normal course of descent.
(1) Ectopic testis (common).
(2) Undescended testis (relatively uncommon).
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5. What is an ectopic testis? What is the commonest position?
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A testis that has strayed from the normal line of descent is termed ectopic. This is uncommon. However, when it does occur, the commonest position is in the superficial inguinal pouch, which lies anterior to the external oblique aponeurosis. The testis reaches this site after migrating through the external inguinal ring and then leaves the normal track of descent to pass laterally. Other situations are the groin, the perineum, the root of the penis and the femoral triangle.
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6. What is an undescended testis? What is the most common place for this to occur?
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This is relatively common. A testis that has followed the normal course of descent but has stopped short of the scrotum is termed an undescended or, more properly, an incompletely descended testis. It may lie anywhere from the abdominal cavity, along the inguinal canal, to the top of the scrotum. The vast majority are due to a local defect in development. The affected testis is always small and it is probable that this imperfect development impairs descent rather than the imperfect descent impairs development. The incompletely descended testis is usually accompanied by persistent patency of the processus vaginalis, presenting as a congenital hernia. Unilateral undescended testes are four times as common as bilateral. The condition of bilateral undescended impalpable testes is termed cryptorchidism. Most, if not all, testes that are going to descend do so within the first few months of life. If the testis is not in its normal scrotal position at puberty, it is very unlikely that it will be capable of spermatogenesis. However, the interstitial cells are functional, so that secondary sex characteristics develop normally.
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7. How much more common is unilateral undescended testis than bilateral undescended testis?
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Correct answer:
Unilateral undescended testis is four times more common.
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8. What is cryptorchidism?
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Correct answer:
This is the condition of bilateral undescended impalpable testes.
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9. What is the differential diagnosis of maldescended testis?
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Correct answer:
Retractile testis.
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10. What are the main features of a retractile testis? What must you look for on examination to distinguish this from maldescent of the testis?
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The commonest mistake in diagnosis is to fail to differentiate a true maldescent from a retractile testis. The retractile testis is a normal testis with an excessively active cremasteric reflex, resulting in the testis being drawn up to the external inguinal ring. It is a common condition and often the parents think that the testes have failed to descend; indeed, when the scrotum is palpated the testes may not be felt.
However, careful examination will probably reveal the testis at the external inguinal ring or at the root of the scrotum and the testis can, by downward stroking or gentle traction, be coaxed into the scrotum.
A useful trick is to place the child in the squatting position for the examination; this often encourages a retractile testis to descend into the scrotum. It is also worthwhile asking the parents to examine the child when he is relaxed in a warm bath; again the retractile testis may then slip into its normal position. If the testis is easily palpable in the groin and remains easy to feel when the child tenses his abdominal wall muscles, it is lying in the ectopic position and not in the inguinal canal – where it is usually impalpable or, at the most, in a thin boy, detected as a vague, tender bulge.
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11. How would you treat a patient with retractile testis?
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Correct answer:
The child with retractile testis is normal; reassurance of the parents is all that is required. The ectopic or undescended testis must be placed in the scrotum if it is to function as a sperm-producing organ.
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12. Can a child with maldescended testis develop secondary sex characteristics?
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Correct answer:
If the testis is not in its normal scrotal position at puberty, it is very unlikely that it will be capable of spermatogenesis. However, the interstitial cells are functional, so that secondary sex characteristics develop.
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13. What are the complications of maldescent of the testis?
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Correct answer:
(1) Defective spermatogenesis, sterility if bilateral. (2) Increased risk of torsion. (3) Increased risk of trauma. (4) Increased risk of malignant disease, even if surgical correction is carried out. (5) Inguinal hernia: persistence of the processus vaginalis.
