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.