Combination of the pedicled penile skin ap with the penile advancement ap as a coverage technique for repair of urethrocutaneous stulas secondary to urethroplasty

Background: The urethrocutaneous stula is a common complication secondary to urethroplasty. The management is complex and not standard yet. We report our experience and techique with combined pedicled skin ap and local skin advancement ap for urethrocutaneous stulas secondary to urethroplasty. Methods: We retrospectively analysed data of 36 cases of urethrocutaneous stulas secondary to different urethroplasties treated from January 2014 to January 2019. All patients underwent treatment with the combination of a pedicled penile skin ap and local skin advancement ap as a coverage technique. The stula size, stula location, number of stulas, and surgical outcomes of stula repair were recorded. Postoperative evaluation included voiding cystourethrography, uroowmetry. All patients underwent postoperative follow-up for 6 to 12 months. Results: Fistula repair was successfully performed in all 36 patients. The overall success rate of urethrocutaneous stula repair was 30/36 (83.3%). Three patients were cured after a second surgery, one was cured after wound dressing, and two were lost to follow-up after failure of the second surgery. Among all patients, the treatment success rate for urethrocutaneous stulas in the coronal sulcus, penis, penoscrotal junction, and perineum was 2/2 (100%), 21/26 (80.8%), 5/6 (83.3%), and 2/2 (100%), respectively. The treatment success rate for small- and large-diameter urethrocutaneous stulas was 23/27 (85.2%) and 7/9 (77.8%), respectively. The treatment success rate for single and double urethrocutaneous stulas was 28/33 (84.8%) and 2/3 (66.7%), respectively. During the 6- to 12-month follow-up, one patient developed a urethral stricture at the urethral stula repair site and was cured by urethral dilation Conclusions: The repair of urethrocutaneous stula secondary urethroplasty induces minimal trauma but is quite challenging for surgeons and has a high failure


Background
Urethrocutaneous stulas (UCFs) are the most common complications after surgical repair of hypospadias and other urethroplasty, with recurrence rates ranging from 0% to 27% [1]. The rate of stula formation also remains problematic for other urethral diseases and improperly performed urethral surgeries. A UCF affects the patient's normal urination can cause recurrent infection of the tissue around the stula and the genitourinary tract, and can result in complications such as urethral stricture, seriously affecting patients' physical health, mental health, and quality of life. Various surgical techniques have been used in the treatment of UCF, and no single technique is suitable or effective for all patients [2]. The incidence of stula formation may decrease with increases in surgeons' experience, reasonable vascularized ap designs, multilayer coverage, and tension-free suturing with appropriate suture materials. We herein report our experience using a combination of the pedicled penile skin ap and the penile skin advancement ap as a coverage technique in repair of UCF secondary to urethroplasty.

Clinical materials
We retrospectively analyzed the medical data of 36 male patients with UCF after urethral surgery in our department from January 2014 to January 2019. The collected data included the stula size, location, and number; the distal urethral obstruction status; the condition of scar softening surrounding the stula; and the surgical outcome of stula repair. The clinical characteristics were listed in Table 1.Their mean age was 25.7 years (range, 10-55 years). Among the 36 patients, 24 UCFs developed after hypospadias repair or as a result of failed stula repair, 2 developed after placement of an indwelling catheter, 2 developed secondary to a urethral calculus, 2 developed secondary to a urethral diverticulum, 2 developed after circumcision, 1 developed secondary to congenital anal atresia, and 3 developed after surgical repair of other urethral injuries. Of all 36 patients, 32 underwent 1 repair procedure and 4 underwent 2 or more repair procedures. We classi ed each UCF according to the stula site; 2/36 (5.5%) were located at the coronal sulcus, 26/36 (72.2%) at the middle penis, 6 /36(16.7%) at the penoscrotal junction, and 2/36 (5.5%) in the perineum. A single stula was observed in 33 patients, and 2 stulas were seen in 3 patients. The mean stula diameter was 8 mm (range, 5-15 mm); 27 stulas had a diameter of <10 mm, and 9 stulas had a diameter of >10 mm.

Preoperative evaluations
The repair procedures were performed with the patient under general anesthesia at least 6 months after the initial operation. Urinary bacteriological examination was performed to exclude urinary tract infection.
An appropriately sized metal urethral probe was used to check for a distal urethral obstruction, and diluted iodine solution was then administered under pressure into the urethra through the external meatus to con rm the exact number and locations of the stulas.

Surgical technique
Methylene blue was used to mark the location of a 2-mm incision made at the edge of the stula. The skin along the marked line at the edge of the stula was incised by a number 15 scalpel. The surrounding tissue was then separated subcutaneously, and the subcutaneous adhesion surrounding the stula was loosened to ensure that the skin of the UCF could be sutured without tension. The unhealthy scar tissue at the edge of the urethral stula was trimmed. A Foley catheter of suitable caliber was inserted into the urethra. An appropriately sized pedicled penile ap was taken from one side of the incision and then inverted to repair and cover the urethral stula without tension. The surrounding subcutaneous tissue was raised from the other side of the incision and used to cover the stula suture site, and a penile skin advancement ap was used to close the incision and thus complete the combined coverage. For distal urethral stula, as coronary sulcus UCF caused by improper electrocoagulation during circumcision, and fresh tissues amenable to coverage were di cult to nd after several failed surgical repairs. After closure of the stula with continuous sutures, we placed a penile skin advancement ap beside the incision to cover the stula and urethra (Fig. 1). For penile UCF due to improper dressing after circumcision, excessive pressure on the penis caused local skin necrosis. After multiple failed repairs, the local skin condition was poor. We designed a one-sided pedicled skin ap and transferred it to close the stula and reconstruct the continuity of the urethra, and a lower-side penile skin advancement ap was then used to close the incision and complete the combined coverage (Fig. 2). For perineal and proximal UCF, a patient developed UCF due to surgical treatment of congenital anal atresia. In this case, a one-sided pedicled skin ap was used to repair and cover the urethra, and an opposite-side skin advancement ap was used to cover and reinforce the stula surface (Fig. 3). Absorbable suture material (6/0 polydioxanone; Ethicon Inc., Somerville, NJ, USA) was used for both the stula repair and skin incision closure. Any overlapping suture lines were noted during the repair procedure. A diluted iodine solution was injected into the urethra through the external meatus to test the effect of the UCF closure. The criterion for success was the absence of uid leakage. Drainage from the incision was established to reduce the risk of hematoma and effusion if necessary, and Vaseline gauze with an elastic bandage was applied after skin closure and maintained for 2 days.

Postoperative management
Prophylactic antibiotics were continued for 3 to 5 days, and the urethral catheter was left indwelled for 5 to 7 days. Postoperative evaluation included voiding cystourethrography, uro owmetry. We de ned successful repair as normal voiding with a peak ow > 15ml/s and no stula recurrence. All patients underwent postoperative follow-up for 6 to 12 months.

Results
All 36 patients enrolled in the study. A pedicled penile skin ap and a local skin advancement ap were successfully used in the present series of patients who had undergone multiple previous operations. No patients developed serious incisional infections after the operation. The overall success rate of UCF repair was 30/36 (83.3%) ( Table 1). Uro owmetry showed that maximum urine ow rate ranged from 17 ml/s to 24 ml/s( mean value 20 ml/s). Cystourethrography indicated continuity of the urethra and no contrast agent extravasation. Among these patients, the repair success rate for UCFs in the coronal sulcus, penis, penoscrotal junction, and perineum was 2/2 (100%), 21/26 (80.8%), 5/6 (83.3%), and 2/2 (100%), respectively. The repair success rate for single and double UCFs was 28/33 (84.8%) and 2/3 (66.7%), respectively. The repair success rate for UCFs with a diameter of <10 and >10 mm was 23/27 (85.2%) and 7/9 (77.8%), respectively. During the 6-to 12-month follow-up period, three patients developed a recurrent stula and were cured after a second surgery, and two patients were lost to follow-up after failure of the second surgery. One UCF spontaneously resolved after wound dressing. One patient developed a urethral stricture at the urethral stula repair site and was cured by urethral dilation.
Discussion UCF formation is a common and frequently discussed complication after surgical repair of hypospadias and other urethroplasties. Possible causes of UCF include a urethral stricture, suture line dehiscence, an inappropriate repair technique with inadequate inversion of the mucosa, the use of inadequate layers for closure, ischemic tissue, or overlapping of the suture lines leading to suture line leakage [3,4]. In the present study, UCFs developed after various urethral diseases and improperly performed urethral surgeries (urethral stricture, urethral stones, urethral diverticulum, circumcision, indwelling catheter, urethroscopy, and other conditions).
Direct closure of a UCF is a commonly performed and technically easy procedure; however, this treatment is associated with a higher recurrence rate [5]. Possible reasons for repair failure are high tension of the direct suture line, leading to suture line dehiscence, and overlapping of the suture lines, leading to suture line leakage [4].
The frequency of UCF formation has decreased with increased surgeon experience, improvements in operative techniques, use of appropriate suture materials and instruments, and coverage of the urethra with well-vascularized tissue [6]. Many studies have shown that placement of a covering layer between the urethra and the penile skin is advantageous for stula repair. Many materials have been suggested as effective covering layer materials, such as a local scrotal dartos ap, external spermatic fascia, a tunica vaginalis ap, and others [ 7,8,9].
Although coverage techniques are now performed as a routine step by most surgeons, each attempted repair further depletes the local tissue and makes the treatment more di cult. The reported recurrence rate of coronal sulcus stulas is substantially higher than that of stulas in other locations. This is probably related to the lack of su cient soft tissue adjacent to the stula and the more pronounced traction effect of erection on the repaired stula as it gets closer to the glans [10]. To avoid this condition, we used a penile skin advancement ap to repair the coronary sulcus or distal UCFs. It is feasible and effective to treat the stula with the penile skin advancement ap in the study. The advantages of this coverage technique are not only closure of the urethral stula but also avoidance of direct communication between the stula and the skin incision. The advancement ap we used can reduce the tissue de ciency and high tension of the incision; bring healthy, well-vascularized tissue over the urethral repair site; and avoid overlapping suture lines.
There is still a high recurrence rate of UCF after multiple operations of hypospadias, the lack of available surrounding materials and poor coverage are the main reasons. We designed the combined coverage technique. In this technique, the vascularity of the pedicled penile ap is maintained because it is harvested from the side opposite of where the skin advancement ap is raised. This procedure may avoid surgical failure caused by a poor blood supply to the skin. The combined coverage ensures stable adhesive formation between the UCF suture site and the penile skin tissue and promotes the healing of the UCF. When the penile skin advancement ap fully covers the skin wound, the principle of longitudinal, tension-free sutures should be followed. According to previous reports, pedicled tissue rotation may compromise the original shape of the penis [11], the advantages of the penile skin advancement ap are that it reduces the tension of the local penile skin and reduces the penile rotation and abnormal appearance.
The site and size of the stula and the quality of surrounding tissues may affect the outcome of stula repair [12,13]. In the present study, the overall success rate of UCF repair was 83.3%, and patients with larger or multiple stulas were more likely to develop recurrence. Additionally, the success rate of perineal stula repair was high in our study. We believe that tissues for a pedicled skin ap and perineal skin advancement ap are relatively abundant in that region, are easy to harvest, and have good blood supplies. Although the number of patients in our study was limited, these characteristics can effectively improve the success rate of UCF repair. No serious infection occurred in any patients after the operation in the study. We believe that tissue coverage with a good blood supply provides more resistance to infection than administration of antibiotics.
Several important principles of successful UCF repair should be kept in mind: tension-free closure, multilayer coverage with well-vascularized tissue, avoidance of overlapping suture lines, and correction of distal obstruction [14,15]. Our surgical experience and results have led to certain recommendations for UCF repair. Previous procedures can adversely in uence the results of subsequent surgical attempts.
Patients whose stulas fail to heal must undergo urethral stula repair 6 months after surgery to soften the tissue induration and decrease tissue fragility. The suture material is another important aspect of proper repair [16,17]. We used absorbable 6-0 polydioxanone sutures in our patients; nonabsorbable or thicker delayed absorbable sutures should be avoided because the suture itself can cause stula tract formation when it remains in place for a prolonged period of time.
Conclusions UCF repair induces minimal trauma but is quite challenging for surgeons. The combined pedicled skin ap and local skin advancement ap for coverage the urethrocutaneous stulas secondary to urethroplasty can improve the success rate. Clinical application has shown that this procedure deserves further promotion.

Declarations
Ethics approval and consent to participate Written and verbal informed consent to participate was obtained from the patients or their relatives and this study was approved by the Ethics committee of A liated Sixth People's Hospital, Shanghai Jiao Tong University.

Consent for publication
Written informed consent for publication of their clinical details and clinical images were obtained from the patients.

Character
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