1.What is cryptorchidism? When the fetus is in the womb, the testicles are located in the abdominal cavity. During the development process, the testes gradually descend. After birth, if the testicles have not descended to the scrotum unilaterally or bilaterally, it is called cryptorchidism, which means there is no testicle in the scrotum or only one side has a testicle. About 3% of full-term male infants are born with testicles that have not descended into the scrotum, and the incidence of cryptorchidism in male preterm infants can be as high as 30%. Among them, cryptorchidism can be divided into high cryptorchidism and low cryptorchidism according to the location where it stays. High cryptorchidism generally refers to the testicle located in the abdominal cavity or near the inner ring of inguinal canal, while low cryptorchidism refers to the testicle located at the inguinal canal or outer ring. 2. What are the causes of cryptorchidism? (1) Endocrine factors: Most bilateral cryptorchidism is due to insufficient maternal chorionic gonadotropin, which affects the physiological process of normal testicular descent. If the testes on one or both sides do not respond to the hormone due to their own defects and lose the power effect of descent, unilateral or bilateral cryptorchidism is caused. (2) Mechanical factors: Most of the unilateral cryptorchidism occurs because the testes encounter obstacles in the process of descending, such as the spermatic cord blood vessels are too short, the testicular lead or inguinal canal is underdeveloped, the testes and retroperitoneal tissue adhesion, the testicular muscle mutation, etc. impede the descent of the testes, so that the testes stay in the abdominal cavity or in the inguinal canal, or some stay above the scrotum, or even take the “off-ramp “3.What are the risks of cryptorchidism to men’s health? (1) Low fertility or infertility: The appropriate temperature for the testicles to produce sperm is 32~36℃. The testicles that do not descend into the scrotum cannot develop normally if they are in the relatively high temperature abdominal cavity, which will cause testicular underdevelopment or atrophy after 2 to 5 years old, and if the age is over 10 years old, they have mostly lost the ability to produce sperm. (2) Testicular tumor: The age of cryptorchid malignancy is mostly after 30 years old. According to literature statistics, the risk of cryptorchid malignant becoming tumor is 18 to 40 times greater than that of normal intra-scrotal testis, while the risk of intra-abdominal testis malignant becoming is 5 times greater than that of inguinal testis. (3) Trauma: If the testicle is located in the groin or above the scrotum, it is easy to be accidentally damaged by external impact or trauma due to its superficial location. (4) Testicular torsion: The testicles of cryptorchid testes may be prone to testicular torsion due to abnormal attachment of the testicular lead, levator muscle or abnormal attachment of the testicular sheath, and the chance of which is significantly higher than that of normal people. Cryptorchid testicular torsion generally manifests as a painful lump in the groin area. (5) Psychological disorders: The absence of testicles in the scrotum, the inferiority complex caused by poorly developed secondary sexual characteristics and the infertility after marriage can bring serious mental trauma to patients and cause psychological abnormalities. 4. Must cryptorchidism be operated? When is the best time for surgery? About 70% of undescended testicles can descend on their own within the first year after birth. However, about 1% of children will always remain cryptorchid. Spontaneous descent of the testes is most often seen in boys born with low birth weight, a large scrotum, and bilateral undescended testes. Spontaneous descent can occur within 6 months of age and is less likely to occur after that, with no possibility of spontaneous descent after 1 year of age. Therefore, for children with unilateral or bilateral cryptorchidism whose testicles have not descended between 6 months and 1 year of age, endocrine therapy can be chosen according to the doctor’s recommendation. The best age for cryptorchidism surgery is before 2 years old. Studies have confirmed that the ideal age for children with cryptorchidism to effectively preserve their fertility is 12 to 24 months after birth. irreversible pathological changes will occur in the testes after 2 years of age, and will gradually worsen with age. If unilateral cryptorchidism is operated before 2 years of age, fertility can be restored to 87.5% of normal, while children with bilateral cryptorchidism will basically lose their fertility in adulthood if they are not treated. For unilateral cryptorchidism patients after puberty, if the opposite descending testicle is normal and the cryptorchidism has atrophy or malignant tendency, orchiectomy is recommended. For patients with bilateral cryptorchidism, depending on the situation, cryptorchidopexy can be reserved or performed.