Undescended testes lying well
outside the normal line of descent, such as in the perineum, femoral
region or contralateral scrotum are rare and their course is not very
well known. Some suggest that this may be the result of an abnormal
location of the genitofemoral nerve with consequent abnormal migration
of the gubernaculum to the wrong site by forming ectopic extentions
known as Tails of Lockwood (1).
Undescended testes are usually ill formed. The
body of the abnormally situated testis may be hypoplastic and occasionally
the epididymis may be completely separated from the body of the testis
or even the vasa efferentia may be elongated. It then appears likely
that the preexisting imperfect development of the testes may have
interfered with the descent (5).
The etiology of retractile testes is a hyperactive
cremasteric reflex which is most prominent between birth and puberty,
specially at 5 and 6 years of age. This is because the cremasteric
reflex is inversly proportional to androgen levels which are lowest
during this period (because of absence of Leydig cells). The reflex
is triggered by low temperature and stimulation of the cutaneous branch
of the genitofemaral nerve supplying the inner thigh (1). As for the
ascending testis, there are two hypotheses to its pathogenesis. The
first describes these testes as being abnormally descended but with
enough gubernacular laxity to reach the scrotum, however as the child
grows up, the ectopic gubernaculum tethers the testis and pulls it
cephalad out of the scrotum (5). The second hypothesis states that
ascent is due to failure of spermatic cord to elongate in proportion
to body growth. This is seen in patients with cerebral palsy (50%)
because of severe spasticity of the cremasteric muscle (7,8).
As for testicular absence, it may be due to agenesis
because of endocrinologic problems (androgen deficiency in-utero)
or a consequence of atrophy secondary to antenatal torsion (9).
Incidence.
Up to 30% of premature male newborns are born
with an undescended testis. However, of term male infants, 3 to
5% are affected. By three months of age, the incidence decreases
from 3-5% to 0.8% and most studies show that this incidence does
not change between 3 months and adulthood.
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Twenty percent of affected babies have nonpalpable testes. Of these,
45% are abdominal, 45% are retractile and up to are 25% canalicular
(1). The other 80% have palpable testes. Out of these 80%, one third
are retractile and will descend spontaneously at puberty. Unilateral
maldescent is about twice as common as bilateral maldescent. The
right testis is affected slightly more often (53%-58%) than the
left (42%-47%) because the latter descends first (3,5,10,11).
Complications of
The Undescended Testes
Infertility.
Men with an undescended testis have
been classically shown to have lower sperm counts, poorer quality
sperms and lower fertility rates than men whose testicles descended
normally (10). In a study of testicular biopsy done at the time
of orchiopexy showed that germ cell density starts decreasing overtime
beginning as early as one year of age. This has been classically
related to the fact that the undescended testis is not lying in
the 33 degree Celsius environment which is necessary for spermatogenesis
(10). A recent study on patients with history of cryptorchidism
found that the sperm counts ranged from 22 to 61 million per milliliter,
motility and morphology were more than 50% in all specimens and
no significant pyospermia, agglutination or hypervicosity. However,
studies of the nucleus showed that the nuclear annulus of the nuclear
matrix was disrupted, thus preventing the ability to organize DNA
into specific loop domains (organization of DNA in 3D domains is
intimately associated with sperm function). The study concludes
that in these patients fertilization occurs, however, the disruption
of the nuclear matrix will prevent further cleavage of the embryonal
cells (12).
Whatever the exact mechanism behind infertility
in patients with cryptorchidism is, it is definite that the risk
for sterility is there. Paternity rates in unilateral maldescent
were not shown to be severely affected, however sterility is almost
definite in bilateral maldescent, if not treated. In retractile
testes fertility is not affected though some report slight decrease
in sperm count and quality (1).
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