Cryptorchidism refers to the failure of one or both testes to descend from the lumbar retroperitoneum to the ipsilateral scrotum according to the normal developmental process, also known as incomplete testicular descent, and is one of the most common congenital disorders of the male reproductive system in pediatric patients. Cryptorchidism includes true cryptorchidism and testicular ectopic (i.e., abnormal descent). In true cryptorchidism, the testicle is located in the normal pathway of descent, often accompanied by an unclosed peritoneal sheath; testicular ectopic means that the testicle has completed its descent in the inguinal canal, but fails to descend to the scrotum and is located subcutaneously, most commonly in the deep subcutaneous fascia outside the external inguinal ring. If cryptorchidism is not treated, the chance of infertility and testicular cancer increases 4 to 5 times compared to normal. Most men with bilateral cryptorchidism are infertile. Cryptorchidism is caused by abnormal testicular descent. There are many factors that cause abnormal testicular descent, and the etiology of cryptorchidism is not fully understood. At present, the cause of cryptorchidism is thought to be related to multiple factors such as endocrine, genetic and physical-mechanical. The common causes are: 1. Congenital testicular hypoplasia makes the testes insensitive to gonadotropins and lose the descending power. 2. Luteinizing hormone-releasing hormone produced by hypothalamus causes lack of LH and follicle-stimulating hormone FSH secreted by pituitary gland, which can also affect the descending power of testes. Most of the cases caused by endocrine factors are bilateral cryptorchidism, while those caused by other factors are unilateral cryptorchidism, and sometimes cryptorchidism can be combined with inguinal hernia. 3.Physical and mechanical factors affecting testicular descent (1) Abnormality or absence of the testicular lead belt that introduces the testicle into the scrotum, so that the testicle cannot descend to the scrotum from its original position. Traction of the testicular lead: The proximal end of the lead is attached to the testis and epididymis, and its end is band-like. Since the scrotum is formed by the outward protrusion of the lower abdominal wall, the main end of the band is mainly attached to the base of the scrotum; some other parts of the band are attached to the pubic tubercle, perineum or medial femur, as its corresponding branches. It occupies a certain space between the groin and the scrotum. In the seventh month of embryonic life, the development of the testis causes significant morphological changes in the surrounding tissues, and in addition to the swelling of the introitus, the spermatic ducts also lengthen and thicken in a varicocele-like manner. Afterwards, the swollen introitus begins to degenerate and contract, and the testis follows the dilated inguinal canal of the introitus, through the internal ring and out of the external ring. In most cases, the testis exits the external ring and follows the scrotal branch at the end of the band and enters the base of the scrotum. If the testis descends and stays in the internal ring of the inguinal canal and the external ring of the inguinal canal, incomplete descent can occur to varying degrees. If the testis does not descend to the bottom of the scrotum, but descends to the pubic region, perineum or femur along other branches at the end of the testicular lead, it becomes an ectopic testis. (2) Intra-abdominal pressure contributes to the descent of the testis into the scrotum: This view suggests that increased intra-abdominal pressure is the original force causing the testis to leave the abdomen and enter the inguinal canal. (3) Anatomical obstruction: The testis needs to descend into the scrotum after the sphincter has fully descended into the base of the scrotum. Cryptorchidism complicated by sphincter non-closure and termination of the sphincter at the pubic symphysis or above the scrotum is quite common, suggesting that abnormal attachment of the sphincter may impede the descent of the testis; in addition, abnormal remnants of the introitus or fascia covering the scrotal population can prevent the descent of the testis.