Imperfect descent of the testis Incomplete descent

The testis is arrested in some part of its path to the scrotum.

Ectopic testis

The testis is abnormally placed outside this path.

Development of the testis

The testes develop from the genital fold medial to the mesonephros (Wolffian body); in early foetal life, they lie in the retroperitoneum below the developing kidneys. The primitive testis is attached to the posterior abdominal wall by the mesorchium, a neurovascular pedicle derived from the lowermost thoracic segments. The mesonephros begins to disappear about the 10th week of intrauterine life but some of its tubules unite with the rete testis to become the vasa efferentia. The Wolffian duct becomes the epididymis and vas deferens. About the same time the precursor of the gubernaculums develops as a fold of peritoneum which can be traced from its attachment between the vas and the epididymis to the region of the developing phallus. The processus vaginalis starts as a dimple of peritoneum about the 10th week and precedes the testis in its journey through the abdominal wall down to the scrotum. The fully developed gubernaculum contains muscle fibres but there is still no certainty as to the part that it plays in testicular descent.

Maternal chorionic gonadotrophin stimulates growth of the testis and may stimulate its migration. Imperfectly developed testes tend to descend incompletely.

Comparative anatomy

Most misplacements of the testis in man are seen as the normal arrange­ment elsewhere in the animal kingdom. The testes of the whale and the elephant are intra abdominal throughout life. Rodents and creatures which hibernate, such as the hedgehog, the mole and the bat, have open inguinal canals. The testes descend into the scrotum ready for the breeding season.

Incompletely descended testis

Incidence

Scorer examined 2000 newborn boys. There was incomplete descent of one or both testes in 4 per cent of full-term infants and in 30 per cent of those born preterm. About 50 per cent of incompletely descended testes reached into the scrotum during the first month of life but full descent after that was uncommon. The incidence in later childhood and puberty is thus around 2 per cent. The genitals of all male infants are examined at birth but the condition is sometimes missed until the boy is examined by a school medical officer. In a few cases, the presence of a hernia, testicular pain or acute tor­sion directs attention to the abnormality. In an examination of 10 000 recruits during World War II, the incidence of incompletely descended testis was 0.28 per cent. In 10 per cent of unilateral cases there is a family history.

Pathology

Incompletely descended testes are often normal until the age of 6 years but by puberty the testis is flabby and poorly developed compared with its intrascrotal counterpart. Histo­logically the epithelial elements are grossly immature and by the age of 16 irreversible destructive changes have occurred which halt spermatogenesis and limit the production of androgens to around half of the normal output.

An incompletely descended testis brought down before puberty often develops and functions satisfactorily.

Clinical features

The condition is unilateral on the right in 50 per cent and on the left in 30 per cent. Arrested descent of both testes occurs in 20 per cent. Secondary sexual characteristics are normal but other abnormalities of the genitourinary tract may be present. The testis may be:

  intra-abdominal, lying extraperitoneally usually just above the internal inguinal ring;

  in the inguinal canal, where it may or may not be palpable. When both testes are impalpable, the condition is known as cryptorchidism (hidden testes) (Fig. 68.1);

   in the superficial inguinal pouch, where it must be distinguished from the much more common retractile testis which may be found in the same condition.

During childhood the testes are mobile and the cremasteric reflex is very active. In some boys, the least stimulation of the skin of the scrotum or thigh will result in the testis disappear­ing to the superficial ring or into the inguinal canal. Simply exposing the parts can have this effect so that the testis appears never to be in its proper intrascrotal position. Retractile testes should be suspected when the scrotum is normal as the scrotum is usually underdeveloped if there is true incomplete descent. After a while the cremaster relaxes and the telltale bulge of the testis reappears only to vanish when the scrotal skin is touched. A retractile testis can always be brought to the bottom of the scrotum by gently milking it from its position in the inguinal region. A diagnosis of true incomplete descent should be made only if this is not possi­ble. In infancy, 80 per cent of inapparent testes are retractile. They are normal and require no treatment.

Hazards of incomplete descent are:

  sterility in bilateral cases;

  pain due to trauma;

   an associated indirect inguinal hernia that is often present and, in older patients, it is frequently the hernia which causes symptoms;

   torsion;

epididymo-orchitis that, in an incompletely descended testis, is extremely rare but of interest because, on the right side, it mimics appendicitis;

  atrophy of an inguinal testis that can occur even before puberty, possibly due to recurrent minor trauma;

   increased liability to malignant disease. All types of malig­nant testicular tumour are more common in incompletely descended testes even if they have been brought down sur­gically. It has been estimated that the chance of a tumour is about 35 times that in a normally positioned testis. Testi­cular tumours are relatively rare and there are no reliable statistics as to whether orchidopexy diminishes the liability.

However, it does improve the prospect of early diagnosis.

Surgical treatment

Operating on very small children needs the highly specialised skills of a paediatric surgeon so orchidopexy is not usually performed before the age of 2 years. Provided that safe anaesthetic services are available, however, testes should be brought down into the scrotum before the boy starts school. It is best to wait until he is dry because it is less easy to man­age the inguinal wound if the child is wearing nappies. In cryptorchidism it is usual to operate on one side at a time.

Orchidopexy

Orchidopexy (syn. orchiopexy) consists firstly, of mobilisation of the testis and spermatic cord and secondly, retaining the testis in the scrotum. The operation is performed through a short groin incision over the deep inguinal ring. The inguinal canal is exposed by division of the external oblique aponeurosis in the direction of its fibres.

Mobilisation begins with isolation of the indirect inguinal hernial sac which is almost invariably present lying anterior to the cord. The sac is diaphanous and fragile but, with care, it can be swept laterally to reveal filmy fibrous strands which join the neck of the sac to the cord. The fibrous bands are divided and the spermatic vessels are dissected free of the peritoneum to which they are adherent until there is sufficient length of liberated cord to place the testis in the scrotum without tension. Division of the cremaster and the coverings of the cord may give a little more length but there is a risk of damage to the tiny vas and testicular artery. The empty half of the scrotum is stretched with a finger passed into it through the inguinal incision to give enough room for the testis.

Retaining the testis in the scrotum can be achieved by a number of means. In some cases it is enough simply to anchor it to the fundus of the scrotum with an absorbable suture. More commonly the testis is placed in a pouch constructed between the dartos muscle and the skin (Fig. 68.2). An alternative to the dartos pouch is to take the testis through the scrotal septum (Ombrédan’s operation).

Failure to bring the testis down

Sometimes a two-stage procedure is successful: the testis is mobilised as far as possible and anchored with a suture. The mobilisation is completed 6 months later. Orchidectomy should be considered if the other testis is normal, especially if the incompletely descended testis is hopelessly atrophic or the patient is past puberty.

Hormone treatment with human chorionic gonadotrophin is only appropriate when there is established hypogonadism.

Ectopic testis

The sites of ectopic testis are:

  at the superficial inguinal ring;

  in the perineum;

  at the root of the penis;

  in the femoral triangle.

An ectopic testis is usually fully developed. Its main hazard is a liability to injury.

Injuries to the testis

Rupture by a blow is uncommon because of its mobility within the scro­tum. Both severe contusion and rupture are associated with a collection of blood around the testis and cannot usually be demonstrated without exploration. The haematocele should be drained and the tunica albuginea repaired after evacuation of haematoma. A very severely damaged testis may have to be removed.

Haematocele. See Fig. 68.3.

Traumatic displacement occasionally follows a blow. The displaced testis usually lies in one of the sites of ectopic testis and can be returned to its normal position by manipulation before it becomes anchored by fibrosis.