Occult penis is a condition in which the penis is hidden in the soft tissue under the pubic symphysis for various reasons, and the appearance of the penis is short, but the development of the corpus cavernosum is still normal. Patients may have difficulty in urination, urinary retention, urinary tract infection, painful erection, difficulty in sexual intercourse, and psychosexual disorders. The classification and diagnosis of occult penis are confusing in clinical work, the pathogenesis is not clear, and there are various treatment options. It is not uncommon to find occult penis in pediatric patients in clinical practice. Epidemiological surveys have found that the prevalence of occult penis among adolescents is 0.68%, second only to prepuce and circumcision. Although occult penis has been paid attention to by clinicians, but due to the inconsistent understanding of its etiology, diagnosis and treatment by scholars at home and abroad, it is easy to cause misdiagnosis and mistreatment in clinical practice. (a) the etiology of occult penis, the early views are: ① excessive obesity, the perineum fat buried penis body; ② foreskin and penis body is not attached to cause the penis is hidden appearance; ③ penis cavernous body root and pubic symphysis separation or penis skin is too short, so that the penis is hidden in the perineum under the skin. In recent years, there are new developments: (1) the penile meatus 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, which makes the penile skin bound to the abdominal wall and hinders the normal development of the penile skin. Embryologically speaking, in the 6th week of embryonic life, the scrotal bulge appears in the urethral ridge on each side, and the top of the cranial side of the urethral ridge is the genital node (embryo), which extends to form the penis and pulls the urethral ridge forward, and the two urethral ridges fuse to form the urethra of the penis, while the scrotal bulge, which initially occurs in the inguinal region, migrates caudally to form the scrotum and scrotal septum. The failure of the horizontal separation of the migration during the development of the male external genitalia, as described above, leads to the fusion of the penile corpus cavernosum with the deep fascia, resulting in adhesions that involve both the penis and scrotum. With regard to the etiology, there are some commonly accepted views: (1) the skin at the root of the penis is not firmly fixed to the body of the penis; (2) the sarcolemma develops abnormally to form fibrous cords; (3) severe circumcision or post-circumcision scars bind the penis in the foreskin; (4) excessive fat on the pubic symphysis; (5) the penile foot at the root of the penis is abnormally low; (6) the attachment of the suspensory ligament to the penis is abnormal; (7) abnormal development of the penis, etc. In China, some believe that the fleshy membrane is directly attached to the anterior part of the penile body or even the neck is the main cause of occluded penis. In addition, the downward shift of the fatty layer of Camper’s fascia and the abnormal accumulation of fatty tissue between the meatus and deep fascia and the thickening and poor elasticity of the meatus aggravate the degree of occultation. (2) Diagnosis of occult penis There is no unified standard for the diagnosis of occult penis in China, which brings difficulties to academic exchange and evaluation of surgical effect, so it is necessary to formulate a unified diagnostic standard. The diagnosis of occult penis must be combined with its classification, and the severity of occult penis should be determined after the type is determined, so that the possible causes can be reflected in the diagnosis and the choice of surgery can be facilitated. Maizels et al. classified cryptorchid penis into: buried penis, webbed penis, fettered penis and micropenis; micropenis refers to penis with normal morphology, but the length and diameter of penis body is significantly smaller than the average value of normal penis of children of the same age by 2.5 standard deviations. The penis with more than 5 standard deviations can be associated with penile cavernous dysplasia, small testes or with incomplete testicular descent, often combined with endocrine abnormalities. Webbed penis is a congenital developmental abnormality, so that the ventral skin of the penis is not completely separated from the scrotal skin and webbed, resulting in a short appearance of the penis, but the dorsal side of the penis is covered with penile skin, no lack of penile skin, penile body development is normal, buried penis is not only the existence of penile skin and penile body separation, and the lack of penile skin, especially the lack of penile skin when inducing penile erection is more obvious; bound penis refers to a history of surgery Crawford et al. classified it into: occult penis, partially or completely buried penis and webbed penis of the penis scrotum, and he believed that buried penis and webbed penis are different degrees of the same lesion. In China, the diagnostic criteria should at least meet the following five points: ① short penis appearance; ② the hidden penis body under the skin is a normal development; ③ push the skin of the penis root backward to see a normal penis body exposed, and the penis body retracts rapidly after release; ④ except other penile deformities, such as hypospadias or epispadias, idiopathic micropenis, etc.; ⑤ except obese infants and children with the penis body partially buried in the prepubic fat pile. The situation. (3) The timing of surgery Currently, there is no uniform understanding of the timing of surgery for occult penis. Some people believe that a significant proportion of children with anaphylaxis will improve or even heal with age or weight loss, and that the development of the penis body will not be affected by not operating on children with anaphylaxis at an early stage. It is advocated that the age of surgical correction of this disease should be postponed as much as possible until after 12-14 years old, because at this age, the androgen level in children’s body gradually increases, the penis develops faster, the appearance of the penis changes more, and the fat in the perineum is redistributed, which is the key age for children with anaplasia to heal themselves. However, most scholars believe that the self-healing of anaphylactic penis does not occur frequently, and that the presence of recurrent glans penis infection and difficulty in cleaning the penis from the prepuce may affect the development of the penis and cause physiological and psychological disorders if surgery is not performed early. It has been shown that many boys become concerned about their external genitalia before puberty, and that even patients who heal spontaneously may experience emotional disturbances while waiting. In light of this fact, some scholars have argued for early surgical correction in children with a clear diagnosis, and By et al. reported a minimum age of 11 months for surgery, suggesting that surgery at 3 months of age is safe. The results of a group of long-term postoperative follow-up by Herndon et al. suggested that surgery should be performed as soon as the patient is diagnosed. (4) Surgical methods The surgery of occult penis is mostly designed according to the etiology and pathological changes of occult penis, and the surgery is designed according to the understanding of the etiology and pathological changes of this disease in different periods. (1) Before the 1970s, it was thought that this disease was mainly due to the narrow ring of the foreskin. The head of the penis could not be exposed, and the penis was hidden under the skin, so the operation was mainly to cut the stenosis ring and transfer the skin on the ventral side of the penis to the dorsal side. This surgery did not remove or cut the fibrous band that restricts the abduction of the penis, so it is difficult to achieve the purpose of exposing the penis. (2) After the 1980s, it was gradually recognized that this disease was due to the hypoplasia of the distal urogenital sinus that normally extends to the genital node during embryonic development, and the procedures were changed to penile body fixation, Shiraki’s procedure, Johnston’s procedure and Maizels’ procedure. All of these procedures were performed with subtle separation and partial dissection of the fibrous connective tissue. Postoperative penile exposure has improved. The main points and characteristics of each procedure are: ①Penile body fixation: longitudinal and transverse sutures are made on the dorsal side of the prepuce to enlarge the prepuce opening and expose the head of the penis. After the introduction of incisions on both sides of the root, the white membrane of the penis is exposed by subtle separation, and then the white membrane of the penis is fixed with subcutaneous sutures. This procedure is simple, and the postoperative penile exposure is improved, but the long-term results are poor. Shiraki procedure: circumferential incision of the outer foreskin along the circumcision, then longitudinal incision at 2, 6, 10 points and 4, 8, 12 points on the inner and outer foreskin plates, respectively, and triangular flap insertion suture. The head of the penis is then exposed. This procedure is only applicable to the occult penis caused by the short penile skin, otherwise, the penile body fixation should be done at the same time. The treatment effect is sometimes less reliable. Johnston’s procedure: The foreskin is dilated and the adhesions are separated. A circular incision is made at the root of the penis to separate the white membrane of the penis. At the root of the penis, the subcutaneous tissue is sutured to the root of the penis and the pubic symphysis, so that the head of the penis is partially exposed. This procedure is more widely used in Europe and the United States. Because the skin at the root of the penis is fixed in a circular fashion, most of the surgical results are very reliable. However, because of the ring incision, the superficial penile veins and lymphatic flow are easily blocked after surgery, so the swelling of the penis is obvious and lasts for a long time. The Maizels procedure combines the Johnston procedure and suprapubic lipectomy to expose the penis. This procedure is suitable for obese children with hidden stems. (3) In the early 1990s, it was recognized that the pathological changes of this disease were mainly due to the abnormal development of the normal elastic structure of the meatus, which became connective tissue and thus restricted the exposure of the penile body. Therefore, the main purpose of the surgery is to remove the dysplastic meatus to expose the penile body, and at the same time to perform penile body fixation and circumcision, that is, Devine’s surgery. The surgical results are satisfactory. In recent years, By et al. [proposed a surgical method for anaphylactic penis, which is also designed for the pathological change of penile sarcoid development, and the surgical results are very satisfactory. The procedure is as follows: the skin of the penis is incised longitudinally on the ventral side of the penis to the root of the penis, and a circumferential incision is made 0.5 cm from the coronal sulcus, and the inner plate of the foreskin is incised deep to the white membrane, and the root is freed and decapitated. The dysplastic membrane between the penis and the skin was excised to expose the dorsal side of the penis up to the level of the pubic bone and the ventral side up to the penile scrotal junction. Radhakrishnan et al. suggested several points for successful treatment of anaplasia: (1) the penile skin should be free as far as possible to the root of the penis; (2) the fibrous band that restricts penile abduction should be cut; and (3) the penile scrotum and the pubic bone should be removed. The dermis at the junction of the pubic bone and scrotum of the penis is fixed with sutures of the deep fascia of the penis; ④ Restoration of the appearance of the scrotal angle of the penis; ⑤ Appropriate pressure bandaging of the penile skin; ⑥ “Z” shaped sutures of the ventral skin. In moderately severe cases, the fibrous band that restricts penile abduction must be removed. In addition, the subcutaneous tissue on the dorsal side of the penis should be fixed to the pubic symphysis and the scrotal meatus to the deep penile fascia. Maizels et al. suggested that fat aspiration would be beneficial in improving the appearance of severe anorectal penis. However, Joseph et al. believe that suprapubic lipectomy alone is unsatisfactory; By et al. do not advocate suprapubic lipectomy or liposuction alone or in combination for the treatment of anaphylaxis. It should be emphasized that simple circumcision should be contraindicated for occult penis. (4) In the last decade, there have been new improvements in the surgical approach. Yoshifumi Sugita et al. designed a ventral midline penile incision, created a diamond-shaped skin notch, cut the dorsal prepuce inner plate, loosened the penis, and transferred the two dorsal flaps to the ventral side to cover the penis. Taiwai Chin et al. addressed the complication of prolonged postoperative foreskin edema by using a modified foreskin spreading procedure, which is less likely to damage the foreskin blood supply and the thinner inner plate helps to reduce edema. john f. redman considered occult penis as a congenital syndrome of short penis body and penis body deficiency, and used the cuff circumcision technique to preserve the inner plate to cover the penis body. MICHAEL D. GILLETT et al. used medium-thickness flap implantation to treat children with penile skin defects and achieved good cosmetic and functional results. track lee et al. adopted a method of separating the lateral foreskin from both sides, with the ventral and dorsal median incision of the inner plate perpendicular to the lateral skin incision, preserving a good foreskin blood supply with satisfactory results. p. brisson et al. avoids circumferential incision of the skin at the base of the penis, reduces postoperative edema, and applies vertical mattress sutures for more secure fixation.