Cryptorchidism overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saumya Easaw, M.B.B.S.[2]
Overview
Cryptorchidism is the absence of one or both testes from the scrotum. This usually represents failure of the testis to move, or descend, during fetal development from an abdominal position, through the inguinal canal, into the ipsilateral scrotum. About 3% of full-term and 30% of premature infant boys are born with at least one undescended testis, making cryptorchidism the most common birth defect of male genitalia. However, most testes descend by the first year of life (the majority within three months), making the true incidence of cryptorchidism around 1% overall.
A testis absent from the normal scrotal position can be:
- found anywhere along the "path of descent" from high in the posterior (retroperitoneal) abdomen, just below the kidney, to the inguinal ring;
- found in the inguinal canal;
- ''ectopic'', that is, found to have "wandered" from that path, usually outside the inguinal canal and sometimes even under the skin of the thigh, the perineum, the opposite scrotum, and femoral canal;
- found to be undeveloped (hypoplastic) or severely abnormal (dysgenetic);
- found to have vanished (also see Anorchia).
About two thirds of cases without other abnormalities are unilateral; 1/3 involve both testes. In 90% of cases an undescended testis can be palpated (felt) in the inguinal canal; in a minority the testis or testes are in the abdomen or nonexistent (truly "hidden").
Undescended testes are associated with reduced fertility, increased risk of testicular germ cell tumors and psychological problems when the boy is grown. Undescended testes are also more susceptible to testicular torsion and infarction and inguinal hernias. To reduce these risks, undescended testes are usually brought into the scrotum in infancy by a surgical procedure called an orchiopexy.
Although cryptorchidism nearly always refers to congenital absence or maldescent, a testis observed in the scrotum in early infancy can occasionally "reascend" (move back up) into the inguinal canal. A testis which can readily move or be moved between the scrotum and canal is referred to as retractile.
Historical Perspective
Cryptorchidism is derived from the Greek words "crypto" (meaning "hidden") and "orchid" (meaning "testicle"). During the last century, cryptorchidism was sometimes restricted to the subset of undescended testes that were not palpable above the scrotum or in the inguinal canal — those that were truly hidden in the abdomen or completely absent. In recent decades the distinction is no longer made in most contexts, and the two terms are used interchangeably. Cryptorchism is an older variant of the same term.
Causes
In most full-term infant boys with cryptorchidism but no other genital abnormalities, a cause cannot be found, making this a common, sporadic, unexplained (idiopathic) birth defect.
Although severely premature infants can be born before descent of testes, there is a strong association of cryptorchidism with low birthweight due to either prematurity or intrauterine growth retardation. In these infants there is usually no evidence of hormonal malfunction. Associated inguinal hernias are common.
Hormonal abnormalities (deficiency or insensitivity to androgens or anti-müllerian hormone) can be demonstrated in a high proportion of those with evidence of undervirilization or ambiguity such as hypospadias or micropenis.
A contributing role of environmental chemicals — endocrine disruptors — that interfere with normal fetal hormone balance has been proposed as well, similar to the effects of diethylstilbestrol exposure. It is rarely possible to implicate a specific chemical exposure for an individual child.
Occasional instances of other genetic defects involving development or function of the gubernaculum have been reported. Homeobox gene mutations can cause cryptorchidism in animals but remain a largely theoretical possibility in humans.
Rare iatrogenic cases have also been reported in which hernia repair or other surgery in the inguinal area resulted in trapping of a testis above the scrotum.
A 2006 study showed that regular alcohol consumption during pregnancy (5 or more drinks per week) is associated with a 3x increase in cryptorchidism, when compared to non-drinking mothers. Other previously known risk factors include exposure to pesticides, low birth weight (including premature birth), gestational diabetes and being a twin[3].
Physical Examination
The most common diagnostic dilemma in otherwise normal boys is distinguishing a retractile testis from a testis that will not/cannot descend spontaneously into thescrotum. Retractile testes are more common than truly undescended testes and do not need to be operated on. In normal males, as the cremaster muscle relaxes or contracts, the testis moves lower or higher ("retracts") in the scrotum. This cremasteric reflex is much more active in infant boys than older men. A retractile testis high in the scrotum can be difficult to distinguish from a position in the lower inguinal canal. Though there are various maneuvers used to do so, such as using a crosslegged position, soaping the examiner's fingers, or examining in a warm bath, the benefit of surgery in these cases can be a matter of clinical judgement.
In the minority of cases with bilaterally non-palpable testes, further testing to locate the testes, assess their function, and exclude additional problems is often useful. Pelvic ultrasound or magnetic resonance imaging can often, but not invariably, locate the testes while confirming absence of a uterus. A karyotype can confirm or exclude forms of dysgenetic primary hypogonadism, such as Klinefelter syndrome or mixed gonadal dysgenesis. Hormone levels (especially gonadotropins and AMH) can help confirm that there are hormonally functional testes worth attempting to rescue, as can stimulation with a few injections of human chorionic gonadotropin to elicit a rise of the testosterone level. Occasionally these tests reveal an unsuspected and more complicatedintersexcondition.
In the even smaller minority of cryptorchid infants who have other obvious birth defects of the genitalia, further testing is crucial and has a high likelihood of detecting anintersex condition or other anatomic anomalies. Ambiguity can indicate either impaired androgen synthesis or reduced sensitivity. The presence of a uterus by pelvic ultrasound suggests either persistent müllerian duct syndrome (AMH deficiency or insensitivity) or a severely virilized genetic female with congenital adrenal hyperplasia. An unambiguous micropenis, especially accompanied by hypoglycemia or jaundice, suggests congenitalhypopituitarism.