Concealed penis is a congenital malformation of penile development in children, which is a result of incomplete development of the distal urogenital sinus that normally extends to the genital node during embryonic period, making the penis concealed under the skin. In recent years, with the attention of clinicians and the increase of obese children, the incidence of occult penis is also increasing. 1. Etiology of occult penis The understanding of the etiology of occult penis has a process of gradual change. 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 spongy body of the penis from the pubic symphysis or the penile skin is too short, so that the penis is occulted under the perineum skin. In recent years, there is a new understanding of the etiology of the occult penis: 1. the penile meatus membrane is poorly developed and has poor elasticity, 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. We often find that the penile fascia of the child is inelastic in the form of fibrous strips, wrapping the penile corpus cavernosum, and these fibrous cords are attached to the penile body. Casale et al. suggested that anaplasia is caused by 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 area, fibrous cords that restrict normal penile extension, and scar stenosis rings after inappropriate circumcision, which can either exist alone or in combination. Walsh et al. suggested that occult penis in newborns and pediatric patients is mostly due to abnormal development of the penile meatus, while in older children and adolescents it is due to excessive accumulation of subcutaneous fat in the perineum.Maizels et al. suggested that occult penis is a group of syndromes caused by multiple causes of poor penile exposure, rather than an individual disorder. He divided the occult penis into pediatric and adolescent types, with the pediatric type being caused by separation of the penile skin from the penile body, and the latter being caused by excessive localized subcutaneous fat accumulation, resulting in separation of the penis from the skin. lim et al. suggested that there are many different pathogenic mechanisms that can elucidate the occult presentation of the penis, with the retractile penis being caused by the underdeveloped fibrous cords attaching the penis to the prepubic tissues. In contrast, Wollin et al. proposed the concept of the buried penis and described its mechanism, suggesting that the buried penis is a congenital malformation in which the penis is buried in subcutaneous tissue, the penile body and glans are well developed, and the defect in the penile skin is attributed to abnormal attachment of the sarcoid muscle layer during embryonic development. Recently, an author has explained the above views in more detail. By reviewing the relevant literature at home and abroad and combining his own observation and research on the disease for more than 10 years, the author proposed four new views on the causes of occult penis: 1. The fatty layer of the fascia does not thin and disappear in the perineum as in normal men, but like women, the fatty layer continues to the root of the penis or even the body of the penis; 2. The perineum There is an abnormal accumulation of fatty tissue in the loose tissue connected between the campers fascia and the deep fascia; 3. Due to the existence of the fatty tissue layer between the penile meatus and the penile fascia, the meatus cannot attach to the penile body from the root of the penis, but directly to the front of the penile body, so that the penile meatus is triangular in shape between the penile body and the pubic symphysis, thus causing the cone-shaped appearance of the occult penis; 4. The flesh membrane of the penis is stunted and becomes a rope-like fibrous tissue with thickened elastic fibers and poor elasticity, resulting in the penile skin and the deep surface of the flesh membrane getting deep fascia cannot be loosely attached, and the penis cannot slide freely under the skin, limiting the penis expansion and contraction, fixing it below the pubic symphysis, and aggravating the degree of occult penis. In summary, it is believed that the direct attachment of the sarcolemma to the anterior end of the penile body is the main cause of occult penis; while the subluxation of the fatty layer of campers fascia, the abnormal accumulation of fatty tissue between the sarcolemma and deep fascia and the poor elasticity of the sarcolemma aggravate the degree of occultation. These four points together constitute the cause of the unique appearance of the occult penis. In addition, it is clinically necessary to distinguish occult penis from prepuce, webbed penis, and micropenis, which are easily overlooked and confused. The prepuce is a small opening that prevents the foreskin from being turned upward to reveal the head of the penis, while the body of the penis is completely exposed and the skin of the penis slides well. A webbed penis is a thin strip of skin that continues from the scrotum to the ventral side of the penis and is usually asymptomatic. Micropenis refers to the normal appearance of the penis, but the spongy body is small. Patients are often combined with bilateral cryptorchidism, testicular hypoplasia, hypopituitarism and obesity and other endocrine abnormalities, and systematic endocrine examination is required for diagnosis. 2. Diagnostic criteria: The recommended diagnostic criteria for cryptogenic penis should meet at least the following five conditions: 1. the penis is short in appearance; 2. the concealed penile body is normally developed under the skin; 3. the normal penile body is revealed when the skin at the root of the penis is pushed backward, and the penile body retracts rapidly after release; 4. other concomitant penile malformations, such as hypospadias or epispadias, idiopathic micropenis, etc. are excluded. 5. The penile body of obese infants and children is partially buried in the prepubic fat pile. However, the above five conditions do not fully reflect the severity of the anaplasia, because the evaluation of the treatment outcome should obviously be related to the severity of the anaplasia, and moreover, the severity and the chosen surgical method sometimes differ greatly. Some scholars define the degree of penile concealment: severe means that the penis is completely concealed under the skin and only the foreskin is palpable in the plane of the abdominal skin. Moderate means that the penis is mostly hidden under the skin, and the head and body of the penis can be mostly exposed by pulling, but it retracts quickly after being released. Wollin et al. reported that 56% of the 43 cases of occult penis treated had undergone circumcision, and Bergeson et al. reported that 42% of the 36 cases treated had undergone circumcision. Therefore, it is important for clinicians to be aware of this condition. The diagnosis of occult penis can be confirmed by pulling the head of the penis and releasing it, and observing the retraction of the penis. The concept and classification of occult penis have not been standardized. According to different pathological characteristics, CrawfordMaizels et al. further classified occult penis into four types: 1. buried penis, 2. hidden penis, 3. webbed penis, and 4. bound penis. The main pathological features of the occult penis are: 1. the penis is fixed by dysplastic fibrous cords in the sarcoid layer, which originate from Camper’s fascia and Scamper’s fascia in front of the pubic bone. 2. the penile skin is poorly fixed, 3. the penis is fixed by dysplastic reticular tissue at the penile and scrotal junction, 4. there are excessive fat pads on the pubic arch, 5. patients who have previously undergone penile surgery usually have scarring The ring-like cords caused by the penis are trapped in the subcutaneous tissue. It should be noted that not every patient has all five of these characteristics. Bergeson considers the penis to be small and inconspicuous, including webbed penis, buried penis, fettered penis and small penis with normal penile development. 3.Surgical treatment 3.1.Surgical principle:Surgery is the only effective method to treat occult penis. Its basic principles: ① enlarge the narrow foreskin opening and lengthen the overly short penile skin; ② remove the fibrous cords and thickened meatus membrane that restrict penile elongation and draw out the occult penile corpus cavernosum; ③ fix the penile root subcutaneously to the white membrane to prevent penile retraction. 3.2. Surgical methods: 1. Devine’s method of anaphylactic penile correction: longitudinal incision of the prepuce, finding and removing the dorsal penis, especially the distal dysplastic cords, and transversely extending the incision and removing the ventral strip of the penis. If the fat pad is thick, the fat pad above the pubic bone is removed, and the lower abdominal skin is fixed to the superficial fascia of the abdominal wall at the pubic bone with non-absorbable sutures, and the penile skin is fixed to the penile body at the root of the penis. 2.At present, the modified Devine procedure is mostly used: a longitudinal incision of about 1,5 cm is made at each of the 2 points and l0 points on the dorsal side of the penis, the narrow ring of the foreskin is cut and completely loosened, the remaining foreskin is circumferentially cut, the fascia around the penis and the fibrous cords and contracted fleshy membrane tissue are loosened, so that the penile body is completely exposed. The white membrane of the penis was sutured and fixed with the anterior pubic ligament and penile skin tissue at 2 and l0 points on both sides of the root of the spongy body of the penis, so that the penile body was straightened and well fixed. The plastic foreskin was trimmed into six flaps, and the flaps were inserted and sutured with “6-0” PGA thread and wrapped with petroleum jelly gauze under pressure, and the catheter was removed 3 d after surgery. The modified Devine surgery was performed by decorticating the penile body and separating it between Buck’s fascia and the white membrane, which is conducive to releasing the fibrous binding of the meatus and can also reduce intraoperative bleeding; the white membrane of the cavernous body at the root of the penis was sutured to the meatus, which is reliable and not easy to retract; through simple suturing, the penile skin and penile body are better fixed. 3.Modified Devine-Johnson procedure: make an arc-shaped incision at 9~3 points on the dorsal side of the penile root, cut the superficial fascia and Buck’s fascia to the white membrane of the corpus cavernosum layer by layer, after sufficient hemostasis, push the skin around the penis backward by hand until the penis is completely exposed in the fatty tissue of the pubic bone, and use No. 7 silk thread at 3, 9 and 12 points to fix the white membrane of the penis root and The dermis and subcutaneous layer were fixed to the pubic fascia with No. 1 silk thread at 3, 9, and 12 points of the white membrane, and the skin was drained for 1 d. The skin incision was closed with 5-0 intestinal sutures. Note the symmetry of bilateral sutures to avoid lateral tilting of the penis; then forcefully turn the foreskin to reveal the foreskin opening, cut it longitudinally, and after turning, this incision almost becomes a transverse incision, keeping the outer plate, and the inner plate can be excised to 0.3 cm of the coronal groove; separate and cut the dorsal penile dysplastic striated tissue, and the ventral lateral superficial fascia and striated tissue, and cut the penile suspensory ligament at the same time to reach the root of the penis. 4.In recent years, more foreign countries have reported the Brisson procedure with satisfactory results. The method is: separate the adhesions between the inner and outer plates of the foreskin and the head of the penis, suture the head of the penis with silk thread, place a catheter, turn the foreskin outward as far as possible, and cut the narrow ring longitudinally at the outer plate of the foreskin at 2, 6 and 10 points respectively. The glans was exposed, and the inner foreskin plate was circumscribed at the junction of the inner and outer foreskin plates to the white membrane of the penis. The skin of the proximal penis was decorticated along the white membrane of the penis to the root of the penis, cut off and excised all the fibrous fascia and ties, and the penile body was loosened and extended and enlarged to form three foreskin flaps of 1 and 5 om equal length along the longitudinal incision, and the inner foreskin plate was incised longitudinally at 4, 8 and 12 points to form three flaps of 1.5 cm equal length, and the inner and outer foreskin plates and flaps were inserted and sutured together to enlarge the foreskin opening. A curved incision was made above the penile root to remove the subcutaneous fatty tissue, and the upper edge should be gradually reduced to avoid the sudden sagging of the penis. The penile suspensory ligament was cut, and the penile body was stretched outward as far as possible, and the dorsal white membrane of the penile root at 2 and 10 points and the prepubic fascia were closed with silk sutures. The dermis of the skin of the penile root and the white membrane of the penile root were sutured with absorbable thread at 10 and 2 points dorsally and 4 and 8 points ventrally to avoid damaging the neurovascular of the penis, and the penis was wrapped with an elastic bandage with pressure for 2 to 3 d. The main point was to cut the penile skin longitudinally from the ventral side to the penile root and circumferentially cut the inner foreskin plate, which was better exposed compared with Devine’s operation and could completely remove the lesioned meatus, the penile The white membrane is fixed with the corresponding prepubic fascia and the skin of the penile root, and the fat pad of the penile root is removed, which can avoid the developed fatty tissue from pulling the penis back. Usually the pathology of the occult penis is characterized by an insufficient outer foreskin plate and a relatively large inner plate, which is manifested by short ventral penile skin, more pronounced after full extension of the penis. Other authors have made the following modification on the basis of the Brisson procedure: after removing the abnormal dorso-ventral fatty tissue of the penile root, the skin of the root is further narrowed to make the penile skin better adhere to the penile body, and the excess part is rotated to the ventral side of the penile body through flap transfer to solve the problem of foreskin shortage. This procedure has the following advantages: 1. the flap is simple to take, the transfer pathway is short, and the operation is easy. 2. the wide basal skin of the cone-shaped penis is cleverly used, which is in line with anatomy and physiology, while the skin is tightly attached and fixed to the root of the penis, pushing the penis out further, which can maintain a good shape and prevent the penis from retraction. 3. the large caliber of the flap base can ensure a good blood supply and is not easy to necrosis. It is especially suitable for cases with severe occult penis and lack of circumcision for the second operation. 5.Traditional shirika surgery method: 1,5~2,Ocm longitudinal incision at 2, 6 and 10 points on the outer plate of the foreskin, with three incisions intersecting at the tip of the foreskin. The outer plate is freed in three triangular flaps and freed to the white membrane of the penis, and the penis is decapitated to the root, and if the penis root is found to be separated from the pubic symphysis, the penis root spongiosum is fixed to the pubic fascia. Then, the inner foreskin plate was incised longitudinally at 4, 8 and 12 points for 1.5-2.Ocm each, and the glans was exposed and a traction line was sewn to pull out the penis. One or two subcutaneous sutures are placed at the level of the white membrane at the dorsal root of the penis and the dorsal foreskin plate near the incision, and the foreskin is pulled downward to expose the head of the penis. The inner and outer flaps of the foreskin are inserted in a jagged suture and interrupted with 6-0 polyester sutures to lengthen the penile skin and expose the penis, then the penis is wrapped with nylon gauze and mesh sand with appropriate pressure and a catheter is left in place. In addition, because of the excessive use of the inner plate of the foreskin, it is easy to develop stubborn foreskin edema after surgery, which affects the appearance. 6, modified Johnstons surgery: reveal the foreskin mouth, first use hemostatic forceps to bluntly separate the adhesions between the foreskin and glans in the foreskin cavity, and use round needle #4 to sew a stitch on the dorsal side of the glans as a traction line. The dorsal side of the foreskin is cut longitudinally, and the incision becomes almost a diamond-shaped incision after turning over. The inner and outer foreskin plates at the incision are separated until Buck’s fascia is exposed, and the dorsal penis is identified and excised, especially the distal dysplastic strips of tissue, showing the deeper dorsal penile vessels and nerves to avoid injury. After complete loosening of the narrow ring of the foreskin, the foreskin is turned completely to reveal the head of the penis and the coronal sulcus, and the incision is closed with transverse sutures. If the loosening is not complete, another longitudinal incision can be made at each of the 3 and 9 points of the prepuce to completely loosen the narrowing of the prepuce. A 1 cm curved incision is made at the root of the penis at 3 and 9 o’clock to separate and expose Buck’s fascia and release the contracted dorsal fibrous band of the penis to allow full extension of the penis. The superficial fascia under the inner plate of the penile foreskin is fixed to the white membrane at the root of the penis, and the penile skin is intermittently sutured. The traction line was removed, and the catheter was left in place and the penis was wrapped with pressure for 5-7 d to reduce and prevent hemorrhagic edema. Postoperatively, oral hexestrol and sedative drugs were administered to prevent pain caused by penile erection. The Johnstons method is widely used in Europe and the United States, and its efficacy is exact. This procedure can effectively prevent penile recession due to the ring fixation of the penile root, but the superficial penile veins and lymphatic return are easily obstructed, penile edema is slow to subside, and the fibrous tissues that pull the penis are not removed, resulting in the penis not being fully extended. In order to seek a better treatment method, the authors changed the Johnstons operation penile root circumcision into a curved incision on both sides, which not only achieved the purpose of fixing the penis, but also avoided the penile vascular and nerve travel area, thus reducing postoperative complications, and also lifted the narrowing of the prepuce, and loosened the fibrous band that restricted penile abduction through this incision, so that the penis was fully exposed and the purpose of correction was achieved. 3.3. Timing of surgery: There are still controversies about the indications for surgery and the timing of surgery for occult penis. Some scholars believe that some occult penis symptoms can be improved or even healed with age. 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 and the penis develops rapidly at this stage, 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 surgery should be performed as soon as possible once the diagnosis is confirmed, in addition, if there is circumcision, the penis is difficult to clean, easy to cause glansitis, etc., without early surgical treatment, which can affect the development of the penis and cause physical and psychological barriers. In addition, as living conditions improve and the environment changes, many affected children become concerned about their external genitalia before puberty, and psychological disorders may occur while waiting for the process of self-healing. We believe that if the diagnosis is clear, the timing of surgery is more reasonable in preschool, which ensures normal penile development and does not affect the psychological growth of children.