1.What is occult penis? The congenital malformation of concealed penis is that the skin of the penis is not normally attached to the penis body, so that the penis is hidden under the skin. It is characterized by the short appearance of the penis, sometimes only the foreskin is seen on the surface of the body, and there is no penile form. The penile body is well developed and located under the skin. When pushing the skin toward the pubic symphysis, the penis can be revealed and the penile skin retracts after releasing. 2.How to classify? Currently, Bergeson’s definition and classification are commonly used clinically, i.e., the general term of penile dysplasia is used to describe a large group of problems in which the penis is normal in size but insufficient in outgrowth. These include occult penis with abnormal fascial development, buried penis associated with subcutaneous fat or giant hernia with syringomyelia, webbed penis with absent penile scrotal angle, and bound penis due to surgical or post-traumatic foreskin opening scar stenosis. Except for fettered penis and obesity-related buried penis which are non-congenital, all other occult penis pathological changes are congenital. 3.How to classify? The severity of priapism is related to the distance of the distal attachment point of the fibrous cord from the coronary sulcus. The closer the distal attachment point of the fibrous cord is to the coronary sulcus, the more severe the degree of priapism. The degree of occult penis can be judged as follows: if the penis is completely hidden under the skin and only the foreskin can be retrieved from the skin of the abdominal wall, it is considered severe; if the penis is mostly hidden under the skin and the head of the penis is pulled, most of the penis body can be exposed, but it retracts soon after release, it is considered moderate; if the penis is less hidden under the skin, but less than the normal penis is exposed, excluding prepuce and micropenis, it is considered mild. 4.How to make a good differential diagnosis? When diagnosing, special attention should be paid to the difference between occult penis and penile dysplasia caused by simple obesity. The penis of such children has normal appearance and structure, and the spongy body is located in the foreskin, but the spongy body of the penis is small and the length is obviously smaller than that of normal children of the same age. In addition, the diagnosis should also pay attention to the careful examination of the head of the penis for the combination of other malformations, such as supra-urethral cleft, hypospadias, etc. Because the occult penis is not fully exposed in vitro, it is easy to misdiagnose if it is combined with other malformations. 5.How to choose the timing of surgery? Due to the size of infants and young children, the prepubic fat layer is thicker and the penis is poorly exposed, so it is recommended that the earliest time for surgery is 3-6 months of age. More scholars know the timing of surgery for pre-school correction, that is, when the child is 2-3 years old, the occult penis has not yet improved and cannot stand up to defecate, then surgery is needed. Most parents are willing to perform surgery at the age of 3 or even earlier, because on the one hand, parents are worried that their children’s short penis will affect their future sexual function and fertility, and they have a strong will to operate; on the other hand, from the children’s point of view, it is not easy to hold the penis when urinating, and they are embarrassed and afraid of being seen, which will cause different degrees of damage to the children’s physiology and psychology, and often the psychological damage is more serious. Although some children get better as they grow older, children with severe occult penis should be given intervention before school age and operated as early as possible. 6. How is surgery performed? The basic principle is to release the abnormal fascial attachment and fix or unfix the penile skin at the root of the penis. At the same time, the pubic angle of the penis and the scrotal angle of the penis are reconstructed, and the skin of the ventral penis and the penile-scrotal junction is used to cover the trauma, so that the penile body can be fully extended anteriorly. Shiraki method Mainly applicable to the surgery of children with severe occult penis, the method of dilating the foreskin opening, taking 4, 8, 12 and 2, 6, 10 points to circumcise the inner and outer foreskin plates about 1 cm long respectively, and staggering sutures on the inner and outer edges of the foreskin, fully preserves the penile skin and solves the problem of insufficient outer plates. This method is similar to the simple circumcision technique, although it makes up for the penile skin, but the fibrous cord-like tissue of the superficial fascial layer of the stretched penile skin is not treated, the penile straightening is not ideal, the penis is poorly attached after surgery, and the penile body is not obviously exposed. And after insertion of suture, the foreskin is not aesthetically pleasing, and at the same time, the incision area of this operation is large, and the skin flap after excessive separation of the inner and outer foreskin plates sometimes occurs necrosis due to ischemia. Maizels method A curved or root circumferential incision is made on the dorsal side of the penis to decapitate the penis, and transverse sutures are made at 3 and 9 points of the narrow circumcision ring with a longitudinal incision. Excess subcutaneous fat and abnormal development of the meatus are removed, while the dorsal fibrous cord of the penile root is released and the skin of the penis root is fixed to the pubic symphysis at the same time, and the penile skin is sutured. This procedure is suitable for occult penis in obese children and can better expose the penile body. Since the incision is at the root of the penis, care should be taken to avoid damaging the penile nerves and blood vessels during the separation. The disadvantage is that the fibrous cord at the head of the penis cannot be effectively treated, which may lead to inadequate exposure of the head of the penis and possible postoperative retraction of the penis. Johnston method An incision is made at the root of the penis as deep as the white membrane of the penis, and the subcutaneous tissue is sutured in full at the root of the penis and ring-fixed to the root of the penis and the periosteum of the pubic bone, so that the head of the penis is fully exposed and the suprapubic fat is removed at the same time. The advantage of this procedure is that the incision is small and concealed, and it has better results for children with occult penis who have too much fat or reoperation. It can effectively prevent penile retraction, but the circumferential incision may have the risk of postoperative obstruction of superficial penile venous and lymphatic return, damage to the dorsal penile nerve and blood vessels, and even lead to persistent postoperative penile edema. In addition, there is insufficient freeing of the fibrous band binding the penis, and the penile extension is not satisfactory. Devine method An incision is made in the midline of the dorsal penis, and the inner and outer foreskin plates are incised longitudinally. After the foreskin is turned over, the original longitudinal incision is changed into a transverse incision, and the penile skin is removed to the root, while the fibrous band that restricts the penis and the suprapubic fat pad are removed, and the penile skin is fixed to the white membrane of the penis root, so that the penis is fully extended and exposed. This procedure protects the dorsal penile neurovascular, but due to the restriction of the intraoperative incision, the surgical field is small, fixing the penile root requires additional larger incisions on both sides of the penile root, and the dorsal longitudinal circumcision cannot correct the pathological characteristics of the ventral side of the foreskin and the dorsal side of the foreskin of the occult penis, and cannot better deal with the fibrous cords at the coronal sulcus of the penis, and the penile extension is not ideal. Brisson method A longitudinal incision is made on the ventral side of the penis to reach the scrotum, the skin of the penis is completely decapsulated, the dysplastic meatus or accumulated fat between the penile body and the skin is removed, and the dorsal side of the penis is revealed up to the level of the pubic bone and the ventral side up to the penile-scrotal junction. The excess inner foreskin plate is trimmed, and then the dorsal penile root white membrane and prepubic fascia are sutured, and the penile root skin and penile white membrane are sutured at 10 and 2 points on the dorsal side and 4 and 8 points on the ventral side, and the penile root skin and deep penile fascia are sutured at 12 and 6 points to avoid damaging the penile nerves, blood vessels and urethra. This method fully releases the abnormally attached fibrous ties on the occluded penis and establishes a good fixed attachment of the penile skin to the penile body. Borsellino method A circular incision is made at the stenotic ring, followed by a cut along the mid-scrotal suture, through which the penile body is passed and completely decorticated from the outer foreskin plate, thus removing the abnormal fibrous fascia completely and directly. If necessary, the suspensory ligament may be removed. The penis is then reinserted back into the outer foreskin plate and sutured. Many of the previous techniques are incorporated: complete loosening of the penis out of the sheath, release of the abnormal fascial attachment, and reconstruction of the pubic angle and scrotal angle of the penis. This method preserves the intact penile skin and reduces scarring by making an incision not on the dorsal but on the ventral side of the penis. Sugita method First, a vertical incision is made in the ventral midline position of the penis to the scrotum, and the stenotic ring is released to expose the head of the penis, forming a diamond-shaped skin notch; the head of the penis is threaded for traction. Then, a circumferential incision is made at the stenotic ring on the right and left edges of the rhombus, and an incision is made in the midline of the inner dorsal foreskin plate to allow two flaps to be attached to the head of the penis, with the body of the penis completely detached. The two flaps are then wrapped around from the dorsal side to the ventral side, and the penile body is pulled to expose it completely. The flaps are then completely covered with skin flaps and trimmed at the root, ventral side, etc. If necessary, the fibrous ring of the prepuce can be removed during the revision. Finally, interrupted sutures are performed. This method is easy to perform, aesthetically pleasing, and can be used in most cases where there is insufficient penile skin. Short-term results are satisfactory, but long-term results require long-term follow-up. Most of the causes of occult penis are different, so in the choice of surgical method, it is not possible to solve all occult penis with a single method. Some patients are psychologically affected and should be taken seriously. The choice of the time of surgery is also important and needs to be weighed in many ways to seize the best time for surgical treatment. Intraoperative immobilization of the white membrane of the penis and the root of the penis can achieve the same results as fixation. Post-operative HCG hormone assisted treatment requires the guidance and follow-up of a professional male surgeon.