I. Overview The occult penis is a congenital malformation in which the penile body develops normally but reveals abnormally. Under normal circumstances, the penile meatus is derived from the superficial fascia of the abdominal wall, i.e. campers fascia (superficial fascia fat layer) and scarpas fascia (superficial fascia deep layer), downwardly migrating to the superficial perineal fascia (colles fascia), which is a layer of fat-free fibrous tissue migrating to the superficial fascia of the abdominal wall, located between the penile skin and penile fascia, with strong elasticity, and the penile skin can The skin of the penis can slide freely. Most scholars, believe that occult penis is mainly due to: (1) poorly developed penile sarcolemma layer and poor elasticity, which restricts the stretching of the penis and makes the penis fixed below the pubic symphysis, resulting in the skin of the penis not attaching to the penile body; (2) abnormal attachment of the sarcolemma muscle to the penile corpus cavernosum, making the penile skin bound to the abdominal wall and hindering the normal development of the penile skin; (3) excessive obesity: a large amount of fat in the perineum buries the penile body. Some scholars believe that occult penis is a short distance between the foreskin mouth and the penis, short dorsal foreskin and long ventral foreskin, more inner plates and less outer plates, foreskin like a bird’s beak wrapped around the penis and not attached to the penile body, many secondary to fat accumulation in the lower abdomen of obese children, especially in front of the pubic bone. Casale et al. suggested that occult penis is due to a combination of factors, including abnormal development of the penile meatus, poor skin attachment at the root of the penis, excessive subcutaneous fat at the prepubic bone, fibrous cords restricting normal penile protrusion, and inappropriate post-circumcision scar stenosis ring constricting penile outreach, which can exist separately or together, with one of these factors being predominant. walsh et al. In neonates and pediatric patients, occult penis is mostly due to abnormal development of the penile meatus, whereas in older children and adolescents, occult penis is mainly due to excessive accumulation of subcutaneous fat in the perineum. Casale classifies occult penis into congenital occult penis, acquired occult penis and occult penis with obesity according to previous surgery and physical examination. Congenital anaphylactic penis is usually characterized by abnormal development of the penile meatus, fibrous cords that restrict the extension of the penis, partial or complete non-attachment of the penile skin to the penile body, and normal development of the penile body, mostly accompanied by prepuce. Acquired occult penis refers to the inappropriate circumcision in children or the scar of the foreskin opening caused by penile trauma that restricts the penis to be exposed. Some scholars believe that the fat accumulation in front of the pubic bone caused by simple obesity buries the penile body, which should be called buried penis. occult penis and buried penis should belong to two different diseases, but most scholars believe that occult penis and buried penis are actually the same kind of disease. Peng et al. divided occult penis into poorly attached penile skin type, prepubic fat accumulation type, and muscle fiber cords restriction type, and the above three conditions often exist together. The abnormal attachment of the muscle fiber cords from the lower abdominal wall to the penile body and the restriction of penile anterior extension are the main mechanism of the lesion, resulting in the inability of the penile body to effectively stimulate the normal development of the penile skin during penile development, making it unable to attach to the penile corpus cavernosum normally, not to mention relieving the prepuce. According to the severity of occult penis and the degree of lack of penile skin it is classified into complete and partial type to guide the utilization of penile covering tissue in surgery. IV. Clinical manifestations Children with occult penis, clinically, all have the appearance of a short, cone-shaped penis, which is hidden in front of the pubic bone. The foreskin looks like a bird’s beak wrapped around the penis and is not attached to the penile body. The skin at the root of the penis can be pushed back to reveal the normally developed penile corpus cavernosum, and the penile body retracts rapidly after being released. Clinical diagnosis and differential diagnosis 1, clinical diagnosis: the diagnosis of occult penis should be in line with the following aspects: (1) the appearance of the penis is short; (2) the normal penis body is hidden under the skin; (3) the normal penis body can be felt by pushing the skin at the root of the penis with the hand, and the penis body retracts rapidly after release; (4) it can be accompanied by prepuce; (5) except for other penile deformities, such as micropenis, penis (5) except for other penile malformations, such as micropenis and hypospadias, both of which not only have short penis appearance, but also have obvious hypoplasia of the penile head and spongy body, and may have abnormal chromosomal and endocrine examination to differentiate. 2. Differential diagnosis: occult penis is a kind of congenital penile development abnormality, which should be distinguished from buried penis, palsy-bound penis, prepuce and micropenis. True occult penis has the characteristics of lack of penile skin, prepuce and normal cavernous development of the penis, and the cavernous body is hidden in the subcutaneous tissue in front of the pubic bone due to poor attachment of penile skin and cavernous body. Buried penis is an acquired condition in which the prepubic fat accumulates due to obesity, causing the penile corpus cavernosum to be hidden in the fat. And prepuce is more common, the foreskin in the tip of the adhesion, can not be turned up, occasionally see pinhole-like prepuce, but the penis body skin exists, and no penile corpus cavernosum development abnormalities, obese children need to be distinguished from cryptogenic penis. Treatment: In the past, it was thought that the penis of children with occult penis would develop into a normal appearance after puberty, and there was no need for orthopedic treatment. However, Devine’s long-term follow-up observations have disproved this view. It is a consensus among scholars both at home and abroad that occult penis cannot be corrected by medical treatment, such as human chorionic gonadotropin (HCG), but if the penile corpus cavernosum of the child is poorly developed after surgical correction, HCG can be used as an adjunctive treatment. Therefore, in a sense, surgery is the only effective option to treat occult penis. 2. Indications for surgery and age of surgery: There are more controversies about the timing and age of surgery, which are mainly decided according to the different causes of the disease: for children with simple obesity, fat accumulation in front of the pubic bone and insignificant penile recession, they can improve on their own with the increase of age and weight loss, and the early stage without surgery does not affect the development of the penis much, so they can heal themselves through non-surgical methods such as weight loss and exercise. However, in children with severe penile regression, considering the possible negative impact on the physiological and psychological development of the child in the future; most scholars advocate surgical treatment, and it is better to choose the time of surgery after 12~14 years old, because at this age, the androgen level in children’s body gradually increases, and the penis develops faster, plus the redistribution of fat in the perineum, which is the key age for children to heal themselves. For children with dysplastic penile membranes, fibrous cords that restrict penile expansion and contraction, as well as after inappropriate circumcision, because they are prone to obstructed urination, glansitis of the foreskin, circumcision is not easy to clean, and cannot have sexual intercourse in adulthood, etc.; and in general, they cannot heal themselves, because this anatomical abnormality is lifelong, so if you just observe and wait, it is bound to bring the burden of the family and the physiological and psychological trauma of the child, and affect the development of the penis. Therefore, most scholars believe that it is advisable to operate as early as possible, and the operation should be performed at the age of 5-7 years old, when the penis has developed to a certain extent. Nowadays, most scholars believe that the self-healing rate of occult penis is low, and there are recurrent glansitis of the foreskin, and it is difficult to clean the prepuce. If surgery is not performed early, the normal development of the penis will be affected, and it will easily cause physiological and psychological obstacles to the children. The minimum age of surgery reported by BRISS ON et al. is 11 months, and it is considered safe to perform surgery at the age of 3 months at birth. According to the physiological characteristics of penile development, the development of penis is faster from birth to about 5 years old, and the development of penis is slower from 5 years old to before puberty. In recent years, there is an increasing trend of occult penis, and there are still differences on the etiology and pathology of occult penis, resulting in more surgical correction methods. In order to explore the ideal mode of surgery for the correction of occult penis, we believe that surgery should be performed early, otherwise it will affect the normal development of the penis and cause physiological and psychological disorders in children. For those with small penile development, HCG can be used after surgery to promote normal penile development.