I. Etiology There is a gradual change in the understanding of the etiology of occult penis. In the early stage, it was thought that it might be caused by: (1) excessive obesity and the fat in the perineum buried the penile body; (2) the appearance of occult penis caused by the non-attachment of foreskin and penile body; (3) the separation of the root of the penile corpus cavernosum from the pubic symphysis or the penile skin is too short, which makes the penis occult under the perineal skin. In recent years, there is a new understanding of the etiology of occult penis: ① the penile meatus membrane is poorly developed and elastic, which restricts the expansion of the penile body; ② the meatus muscle is abnormally attached to the penile corpus cavernosum, so that the penile skin is bound to the abdominal wall, which hinders the normal development of the penile skin. It is different from the fat accumulation at the base of the scrotum of the mons pubis due to obesity, and the penis is deeply hidden under the skin, which can return to a normal state after maturation and reduction of fatty tissue. Second, the diagnostic criteria 1, the penis appearance is short and the foreskin is bird’s beak-shaped. 2.Hidden under the skin is a normally developed penile body with a positive penile squeeze test. 3, forcefully push back the skin of the penis root to see a normal penile body revealed, and the penile body quickly retracted after release. 4.Excluding other concomitant penile deformities, such as hypospadias or epispadias, idiopathic micropenis, etc. 5.Excluding the situation that the penile body of obese infants and children is partially buried in the prepubic fat pile. Differential diagnosis 1, prepuce Prepuce refers to the narrow opening of the foreskin, can not turn up the foreskin to reveal the head of the penis, while the penis body is completely exposed, the penis skin sliding good. 2, webbed penis The appearance of webbed penis can be seen from the scrotum there is a thin skin continues to the ventral side of the penis, generally without any symptoms. Small penis refers to the normal appearance of the penis, but the spongy body is small. Patients often combine bilateral cryptorchidism, testicular hypoplasia, hypopituitarism and obesity and other endocrine abnormalities, and systematic endocrine examination is required for diagnosis. Some scholars believe that some occult penis can be improved or even healed with age, and surgery is not necessary if the foreskin can be turned up to expose the head of the penis. Therefore, it is advocated that the age of surgery should be postponed to 12-14 years old because the androgen level in the body gradually increases at this stage and the penis develops quickly, which is the key age for healing. Most scholars also believe that self-healing does not often occur, and the skin of the penis is bound to the abdominal wall, which prevents the normal development of penile skin, and the shortage of skin is becoming increasingly serious with age, so it is believed that once diagnosed, surgery should be performed as soon as possible, in addition, if there is a foreskin, penile cleaning difficulties, easy to cause glansitis, etc., without early surgical treatment, can affect the development of the penis, resulting in physical and psychological barriers.