I. Definition of cryptorchidism Cryptorchidism is the most common abnormality of the male endocrine system. It occurs in nearly 3% of full-term infants and 30% of preterm infants. Most can descend into the scrotum at 3 months of age and will not continue to descend beyond 6 months. The testis can be located anywhere between the abdomen or the abdominal cavity to the scrotum. Ectopic cryptorchidism is usually located superficially in the groin. 5-10% of patients with cryptorchidism are bilateral and 20% are inaccessible in the groin. It may be accompanied by abnormal sexual differentiation (DSD). Etiology 1. Normal testicular descent occurs at 30-32 weeks of gestation and requires a normal hypothalamic-pituitary-gonadal axis, and testosterone and DHT. 2. Insufficient intrauterine testosterone. 3.More than 90% of patients with cryptorchidism have epididymal abnormalities. III. Diagnosis 1. Physical examination with skin lubrication. 2.Ultrasound and MRI usually have false positives, ultrasound has 45% sensitivity and 78% specificity, MRI requires anesthesia and is not widely used. 3.Impalpable cryptorchidism is 80% in the abdominal cavity, and complete testicular atrophy accounts for 20%. Laparoscopy is helpful for diagnosis and treatment. 4. Endocrine assessment of the presence of testicular tissue (B-HCG stimulation test, MIS assessment) is needed for bilateral untouchable cryptorchidism. 5. The purpose of diagnostic laparoscopy is to understand the presence or absence of untouchable cryptorchidism, location and anatomy of the testes. 6.Retracted testis can be pushed into the scrotum by hand during physical examination. Surgery or hormone therapy is required, and follow-up until puberty or when the testis no longer retracts is needed. 7. Acquired cryptorchidism can be initially in the scrotum and has changing features on physical examination, usually starting with retraction of the testicle, after which it can no longer be pushed into the scrotum. Its germ cell function is abnormal and comparable to cryptorchidism. The purpose of cryptorchidism surgery is to prevent damage to the testes, including spermatogenic potential or endocrine function, to obtain a normal position of the testes permanently fixed in the scrotum, to make them easily accessible, to obtain normal thermoregulation, and to reduce trauma damage. V. Time limit for cryptorchid surgery The surgery should be performed 6-12 months after birth. There is no definite conclusion on whether early testicular fixation protects against malignancy. All patients who have undergone surgery for cryptorchidism need to be followed up closely throughout their lives.