Cryptorchidism, or undescended testis, is the absence of a testicle in the scrotum. It is due to a defect in migration of the testicle during fetal life at any point of its normal course: between the lumbar region where it is formed, and the scrotum where it should be at birth. In the case of testicular ectopia, although the testis is also absent from the scrotum, the latter is located outside its normal course of migration.

Cryptorchidism most often corrects itself spontaneously during the first year of life. After this period, if the testicle has not descended, treatment is necessary to avoid the risk of complications.

The word cryptorchidism comes from the Greek “kryptos”, which means “hidden” and from “orkhis”, which means “testis”. This is an abnormality of the male genital system that results from a defect in the migration of one testicle, or even both testicles, which, starting from the abdomen, does not descend into the bursa (or scrotum ) during fetal life. This is why we speak of “undescended testicle”. One, or even both bursaries are then empty and the testicle is present, more or less high, on its migration path: the testicle is located in the abdomen once in four, but most often, it is in the inguinal canal and lies more or less close to its external orifice and to the scrotum. 

In 80% of cases, a single testicle did not descend, with a slightly greater frequency on the left. In this case, the cryptorchidism is said to be unilateral. In 20% of cases, it is said to be bilateral.

Cryptorchidism affects 20-30% of premature boys and 1-4% of full-term infants. Very premature babies are more affected by this disease.

Testicular ectopia, an uncommon disease, differs from cryptorchidism in that, although the testis is also absent from the bursae, the latter is located outside its normal path of migration. It can indeed be located in:

• The retroperitoneal area, on the left of the abdomen, at the same level as the navel;
• The pre-penile area, in the middle of the abdomen, on a vertical axis between the navel and the penis;
• The two femoral areas, on both sides of the penis, at the junction between the legs and the abdomen;
• The perineal zone, between the penis and the anus, on an axis slightly shifted to the left. 

The origin of cryptorchidism is poorly understood. The most probable hypotheses put forward:

• a mechanical obstacle to migration: narrow inguinal canal, too short spermatic vessels and nerves, fibrous obstruction of the scrotal opening, abnormal adhesion of the fetal testis to the retroperitoneal tissue;
• an anatomical abnormality;
• a hormonal problem during pregnancy, which may explain why the testicle does not migrate into the bursa, such as insufficient production of male hormones (androgens) or high exposure to female hormones (estrogen).

There are several risk factors:

• prematurity, low birth weight or breech birth;
• a family predisposition: existence of urogenital malformations in the father or the brothers (cryptorchidism, hypospadias, micropenis);
• exposure to endocrine disruptors capable of disrupting the action of hormones during pregnancy.

Cryptorchidism shows no functional signs apart from complications. Indeed, if the testicle does not descend and in the absence of treatment, may appear: 

• An inguinal hernia associated with cryptorchidism in 65% of cases;
• Testicular torsion, which alters the vascularization of the testicle and must be treated urgently, by surgery;
• A testicular trauma that can occur during groin pressure if the testicle is in the inguinal position;
• Psychic and aesthetic disorders;
• Testicular cancer, the leading cause of cancer in men between 20 and 35 years old;
• Sterility, present in 10% of cases of unilateral cryptorchidism and up to 50% of cases of bilateral cryptorchidism, and which can be explained by the fact that, when the testis is not in the scrotum, it is not at the correct temperature, 33-34 ° C, to properly manufacture sperm. Male infertility then results either from a low quantity or absence of sperm in the semen, or from the presence of abnormal sperm.

Cryptorchidism resolves itself in two thirds of cases spontaneously within the first year of life; its frequency is only 1% at the age of 6 months.

After the first year, if the testicle has not descended, treatment becomes essential to avoid the risk of complications, the intra-abdominal position of the testicle disrupting spermatogenesis and increasing the risk of cancer. The treatment depends on the higher or lower position of the testicle. The options available include:

• Medical treatment, possible if there is no anatomical obstacle to testicular descent. This consists of a series of injections of human chorionic gonadotropic hormone, or HCG, intramuscularly. Its efficiency is of the order of 30%;
• Surgical lowering with orchidopexy, that is to say fixation of the testicle inside the scrotum, to be undertaken early, from the age of 2 years. The procedure involves two small incisions, one in the groin and the other in the lower part of the scrotum. It consists of freeing the testicle from its attachments and restoring maximum length to the vessels and channels that accompany it. The testicle is then fixed in the scrotum so that it cannot come up. If the length of the spermatic cord is sufficient, the surgical act is performed in one step, which is the case in 90% of procedures. Otherwise, a second operation may be necessary. Surgical treatment can reduce the risk of infertility by half. On the other hand, it does not reduce the risk of testicular cancer, but facilitates medical monitoring of the testicle;
• An orchiectomy: if during the surgery, the testicle appears very small or poorly vascularized, it is likely to be removed because it will be of no use and may be the cause of complications. The subsequent placement of a testicular prosthesis can then be considered.