Does Double-Layer Vascularized Dartos Flap with Snodgrass Hypospadias Repair Improve Results?

ABSTRACT

Purpose: To evaluate the importance of using a double-layer vascularized dartos flap for preventing fistula in Snodgrass hypospadias repair.

Patients and Methods: This study was carried out in the departments of plastic surgery and urology at Al-Azhar University hospitals. The study included 40 patients with primary hypospadias, aged 2 to 22 years (mean age 8.6), and operated from September 2008 to August 2010. Of the 40 patients, 32 had distal hypospadias and 8 had mid-shaft hypospadias. The standard technique of tubularized incised plate (TIP) urethroplasty (Snodgrass procedure) was done with additional double-layer dartos fascia flap coverage. The mean follow-up period was 4.5 months (range 3 to 12 months).

Results: Successful repair of the 40 cases was achieved. Urine flow results were excellent with a normal-looking, slit-like meatus. Two patients (5%) had meatal stenosis at the early postoperative period, which was corrected by urethral dilatation of the external meatus at an interval of up to 2 months, whereas urethrocutaneous fistula developed in 1 patient (2.5%).

Conclusion: A urethral covering dartos flap transposed ventrally with Snodgrass procedure showed a reduced incidence of fistula complication in our hands after hypospadias repair.

Taman Essam, Ismail Hassan, Salah Elwagdy

Submitted: July 7, 2011

Accepted for Publication: September 2, 2011

KEYWORDS: Hypospadias; Snodgrass procedure; Double-layer vascularized dartos flap

CORRESPONDENCE: Salah Elwagdy, MD, Department of Uro-radiology, Azhar University, Cairo, Egypt ().

CITATION: UroToday Int J. 2011 Dec;4(6):art 69. http://dx.doi.org/10.3834/uij.1944-5784.2011.12.02

INTRODUCTION

Hypospadias is a congenital anomaly due to incomplete tubularization of the urethral plate leading to abnormal location of the meatus anywhere along the ventral aspect of the penile shaft and down on to the perineum. Hypospadias is a common clinical problem that occurs in 1 out of 200 to 1 out of 300 live male births. In over 80% of cases, the meatus is located distal to the mid-shaft [1].

The most important development in modern hypospadiology is recognition of the urethral plate, which comprises tissues distinct from glans and penile skin that normally should have formed the urethra. This plate consists of surface epithelium overlying well-vascularized connective tissue, which can be preserved for urethroplasty, rather than fibrous “chordee” bands previously thought to cause ventral curvature [2].

In the past, Snodgrass tubularized incised plate (TIP) urethroplasty became a preferred technique for distal hypospadias repair and subsequently gained worldwide popularity and acceptance. The procedure gives functional results and a cosmetic appearance that is superior to that obtained by flip-flap or onlay preputial-flap repairs. In addition, this procedure is associated with a fairly low rate of complications [3].

The aim of surgery in hypospadias is to achieve a functional penis with a normal cosmetic appearance. Snodgrass repair, with additional facial coverage, creates a vertical slit-like, normal-appearing meatus. This procedure allows the construction of the neourethra from the existing urethral plate without additional skin flaps. The technique is versatile and suitable for almost all distal lesions [4].

Urethrocutaneous fistula occurring after hypospadias repair remains a frustrating problem for surgeons. Furthermore, with the improvement in suture material and surgical techniques, such complications are increasingly unacceptable [5].

Fistula rates have still been reported to be as high as 5% from large center, multiple surgeon studies and 16% from smaller center studies. Some researchers advocated routine use of a vascularized dartos flap in conjunction with Snodgrass repair and a 2-layer closure of the neourethra [6]. More recent studies [7, 8] suggested double-layer covering of the new urethra with a dartos flap.

In this work, we evaluated the importance of a urethral covering using a double-layer vascularized dartos flap in fistula prevention after Snodgrass repair.

PATIENTS AND METHODS

Between September 2008 and August 2010, 40 patients with primary hypospadias were enrolled in the study. Their ages ranged from 2 to 20 years (average 8.6). They underwent hypospadias repair in the departments of plastic surgery and urology at Al-Azhar University Hospital. Thirty-two of the patients had distal hypospadias and 8 had mid-shaft hypospadias. A preliminary retrograde urethrogram was performed for each patient to exclude any other abnormality along the urethral course. Thirty-one patients were operated on under general anesthesia while 9 patients had spinal anesthesia. Optical magnification was used in all patients. A tourniquet was applied to maintain a bloodless field.

A straight penis was confirmed by performing a vasoactive stimulated erection to assess any erection curvature.

The standard technique of TIP urethroplasty (Snodgrass procedure) was performed. A U-shaped incision was made, extending along the edges of the urethral plate to healthy skin 2 mm proximal to the meatus. The urethral plate was widened by a midline incision along its entire length from the meatus to the glans tips. The incised plate was then tubularized over a 10 Fr silicone catheter in 20 patients (50%), a 6 Fr stent in 14 patients (35%), and a 16 Fr stent in 6 patients (15%) using interrupted polyglycolic acid (vicryl no. 6/0 or 5/0) sutures. Dartos flaps were mobilized to a tension-free, covering-repaired, hypospadias tube. The second layer of the vascularized dartos flap was used from the subcutaneous tissue of the dorsal preputial skin and transposed to the ventral side. Then the dorsal prepuce covered over the flap. At the end of surgery, gauze dressing was applied, moistened with disinfected antibiotic cream (Gentamycin). Postoperative pain was managed with regular paracetamol or non-steroidal analgesic suppository (NSAID) diclophenac sodium. All patients were maintained on intravenous antibiotics within the first 3 days then shifted to oral form to complete a period of 10 days. Urethral stents were removed on the seventh postoperative day and parents were advised to start urethral dilation twice per day for 3 months. Patients followed up for 6 months to 1 year.

RESULTS

Retrograde urethrography excluded the presence of any stricture along the urethral course in all patients in the present study.

All patients underwent repair. Of them, 32 cases had distal hypospadias and 8 cases had mid-shaft hypospadias. Cosmetic results were excellent with this repair, with a normal-looking, slit-like meatus.

Four patients had meatal stenosis in the early postoperative period, which was corrected by urethral dilatation of the external meatus for up to 2 months postoperatively.

Urethrocutaneous fistula developed in 1 patient and was repaired successfully. The hospital stay was 48 hours to 5 days (mean 3 days).

Table 1 compares the site of meatus, operative time, and complications of TIP.

DISCUSSION

In this work, we followed the general principles of hypospadias repair, including the minimal use of cautery, avoidance of tension, the use of well-vascularized tissue, closure in as many layers as possible, the use of loupe magnification and identification, and the relief of any obstruction. Because the urethral plate was present and wide enough, we elected for TIP urethroplasty. Using that technique, we have had satisfactory results comparable with previously mentioned series [3,7,9,10]. Indeed, the complication rate of 5 (12.5%) in 40 is less than those reported previously in older series [11,12] of 24% and 15%, respectively.

This may be due to the inclusion of few patients with previous plate incisions in their series while none of our cases had a history of previous urethroplasty. These favorable outcomes may be predicted by clinical observations and animal studies that consistently find that incision into the dorsal midline of the urethral plate heals with no significant gross or microscopic fibrosis [13].

The dorsal relaxing incision over the urethral plate results in a neourethra of more than 10 F and does not seem to compromise the blood supply of the urethral plate. It also results in re-epithelialization rather than fibrosis of the subcutaneous tissue, which may later give rise to stricture of the neourethra [14]. They concluded that TIP urethroplasty can be used for hypospadias reoperation even when the urethral plate has been incised previously, but it should be avoided when the urethral plate is obviously scarred or has been resected.

Fistulae after TIP reoperation may be partly attributable to the relative lack of tissues available for coverage over the neourethra suture line. Borer et al. (2001) noted that 4 out of 5 boys who developed fistulae in their series had no barrier layer interposed over the urethra, and they recommended mobilization of a dartos or tunica vaginalis flap to reduce the incidence [12]. They described the creation of a dartos flap from subcoronal shaft skin and reported only 1 fistula among their 13 patients. In the present series, dartos was used from the prepuce, but the fact that the fistula occurred when adjacent tissues were sutured over the neourethra probably illustrates the need for a flap to be developed that can be secured over the urethra by laterally based sutures; otherwise, sutures from the neourethra, barrier layer, and skin closures may overlap.

Cheng and associates [6] reviewed the records of 514 patients, including 414 with distal and 100 with mid-shaft or proximal hypospadias. All cases underwent primary 1-stage hypospadias repair with the Snodgrass technique in conjunction with vascularized dartos flap coverage. All 6 surgeons in each case, which included a 2-layer closure of the neourethra, preservation of the well-vascularized periurethral tissue, and routine use of the vascularized dartos-flap coverage, used a nearly identical surgical technique.

Stents were used in 292 of the 514 repairs. Of the 414 distal cases, there were no fistulas and 1 case of meatal stenosis. Of the 100 proximal cases, there were 3 fistulas and 1 case of meatal stenosis. The overall complication rate was less than 1% for all cases combined.

In 2003, Samuel and Wilcox [15] also used a second layer of vascularized pedicle subcutaneous tissue harvested from the dorsal hooded prepuce to cover the urethroplasty to minimize the incidence of urethrocutaneous fistula. However, Sozubir and Snodgrass [16] mentioned that a dartos pedicle flap obtained from the dorsal prepuce and shaft skin is preferable when covering the neourethra.

In our series, the incised urethral plate was tubularized without tension over a catheter of an appropriate size (6 Fr to 16 Fr) using continuous subepithelial (non-interrupted) 6/0 polyglactin sutures. Then, the corpus spongiosum alongside the plate was sutured together over the neourethra with the Y-to-I technique according to the Yerkes et al. method [17]. A second layer of vascularized dartos pedicle flap was harvested from the dorsal prepuce, or penile shaft skin in circumcised patients, to cover the suture line after TIP urethroplasty. We think that this combined technique has resulted in a functional and cosmetically preferred outcome.

There is much debate about routine meatal dilatation after TIP. In 2002, Elbakry [18] considered postoperative regular urethral calibration as an integral part of the TIP urethroplasty to prevent the neourethra and/or meatal stenosis with subsequent urethral fistula. On the other hand, in 2002, Snodgrass and Lorenzo [14] concluded that dilatation of the neourethra is unnecessary after TIP urethroplasty, and the calibration and uroflometry after 6 months of surgery may be useful to detect subclinical obstructions.

They attributed the meatal stenosis detected in another series [18] to technical error, including failure to deeply incise the plate and/or tubularization of the urethral plate too distally.

However, the key point in prevention of meatal stenosis might be the length of the dorsal incision of the urethral plate, which should not touch the dorsal lip of the anticipated neomeatus. Nevertheless, in 2005, Stehr and coworkers [3] reported meatal stenosis in 2 (5%) primary cases and in 2 (5%) secondary cases.

Urethrocutaneous fistula was seen in 2 patients (5%) in secondary cases, despite the deep incision and adequate tubularization of the urethral plate, and the patients were kept under regular calibration in an outpatient clinic.

In 2008, Snodgrass [2] suggested that tubularization should not extend beyond the mid-portion of the glans wings, which is about 3 mm from the tip of the plate. The neomeatus should be oval, not rounded, as in a normal child.

As is found in several studies, the 2 most common complications of TIP are meatal stenosis and urethrocutaneous fistula. However, in 2004, Sharma [19] reported the occurrence of unusual complications after Snodgrass technique, such as complete dehiscence of repair in 1 patient out of 35 cases, and superficial extravasation of urine in another case. A recent review of worldwide literature from 1994 to 2004 found overall complications in 9% (0 to 21%) [2].

In 2005, Stehr and colleagues [3] performed 100 primary TIP urethroplasties in patients with distal hypospadias. The age of the patients at the time of surgical correction was 16 months to 10 years, with a mean of 41.4 months. All patients underwent the procedure under general anesthesia supplemented by additional pain management with penile block anesthesia or caudal anesthesia. During follow-up (23.5 months), urethrocutaneous fistula occurred in 5 cases (5%) and meatal stenosis in 17 cases (17%).

There were no other complications, and the cosmetic results were good in all cases.

In 2006, Djordjevic and coworkers [10] evaluated the importance of a urethral covering using vascularized dorsal subcutaneous tissue for fistula prevention after Snodgrass technique in 126 patients, aged 10 months to 16 years. Of the patients, 89 had distal hypospadias, 30 had mid-shaft hypospadias, and 7 had penoscrotal hypospadias. A longitudinal dorsal dartos flap was harvested and transposed to the ventral side by the buttonhole maneuver. None of their cases had fistula. In 6 patients, temporary stenosis of the glandular urethra occurred and was solved by dilation. They concluded that redundancy of the flap and its excellent vascularization was dependent on the harvesting technique.

In a study performed by Mustafa and coworkers in 2008 [7], they used TIP with a double-layer covering of the neourethra by subcutaneous tissue in 26 patients with primary hypospadias, aged 2 to 22 years (average 8.6). Of the patients, 21 had distal hypospadias, 3 had mid-shaft hypospadias, and 2 had penoscrotal hypospadias. The mean follow-up period was 4.5 months (range 3 to 12 months). Successful results of a normal-looking penis without fistula was achieved in all patients. One patient had meatal stenosis (3.84%) at the early postoperative period, which was corrected by urethral dilatation.

On the other hand, in 2008, el-Kassaby et al. reported a double-breasted, de-epithelialized penile skin flap used as covering tissue after TIP repair in 764 cases. They reported fistula formation in only 2% of their cases [20].

In 2009, Sarhan and associates [21] reported on TIP urethroplasty in 500 cases; 439 (87.8%) had primary hypospadias and 61 (12.2%) had 1 failed previous repair. The hypospadias defects were coronal in 110 (22%), distal penile in 261 (52.2%), mid-penile in 78 (15.6%), and proximal in 51 (10.2%). Chordee was present in 98 (19.6%) patients.

The overall success rate was 81.4%. Reoperation was required in 93 patients (18.6%), for urethrocutaneous fistula in 47 (9.4%), complete disruption of the repair in 32 (6.4%), and meatal stenosis in 14 (2.8%). In univariate analysis, complications were significantly higher in stented repairs, posterior hypospadias, those with no neourethral coverage (spongioplasty), and repairs early in the study. The last 3 factors were the only significant independent risk factors in multivariate analysis.

In a recent study, Abolyosr [8] evaluated the neourethra covering created by a vascularized, overlapping, double-layered dorsal dartos flap for preventing urethrocutaneous fistula in the Snodgrass hypospadias repair in 156 boys (mean age 4.5 years). A preoperative position of the urethral meatus was subcoronal in 37, at the distal shaft in 61, and mid-shaft in 58. With a mean follow-up of 23 months (range 6 to 42), all boys had satisfactory, subjective, cosmetic and functional results. No urethrocutaneous fistula or urethral stenosis occurred.

More recently, Eassa and associates [22] presented 10 years of experience with TIP urethroplasty in 391 patients. The median age at surgery was 2 years (range 0.5 to 16). The median follow-up was 11 months (range 3 to 96). A total of 52 reoperations were required because of fistulae (25/6%), neourethral disruption (13/3%), meatal stenosis (13/3%), and stricture (1/0.3%). The reoperation rate was significantly higher in the presence of interrupted sutures, chordee requiring dorsal plication, penoscrotal or proximal shaft defects, a lack of neourethral vascular tissue coverage, and in children over 4 years of age. Multivariate analysis identified the last 3 of these variables as independent risk factors for reoperation.

In spite of the general agreement between researchers regarding the use of urethral stents after TIP, recent reports suggested stent-free repair. Turial and colleagues [23] reported their experience with TIP repair without placement of a postoperative urethral stent in 41 cases (60% with coronal or distal hypospadias and 40% with mid-shaft hypospadias). Their ages ranged from 6 months to 16 years (median 3 years). In 7 cases, the prepuce was also reconstructed. There were 2 cases with fistula and 1 case of meatal stenosis. No glans dehiscence, severe bleeding, or wound infection was observed. No urinary retention requiring catheterization was observed, irrespective of age. All but 1 patient was discharged the day after surgery. Follow-up ranged from 8 to 48 months (average 22 months). Most parents (87.5%) were satisfied or very satisfied.

The major limitations of our study are the small number of cases and the absence of a control group and a lack of randomization.

CONCLUSION

Our surgical experience over the last 2 years has emphasized that TIP urethroplasty with neourethra coverage using double-layer vascularized dartos pedicle flap of dorsal preputial skin is versatile and single-staged, and a simple operation in the management of different types of distal and mid-shaft hypospadias. In addition, the choice of fine suture materials of good quality and the use of magnification tools have contributed to improved procedural outcomes.

ADDITIONAL IMAGES

REFERENCES

Baskin LS, Himes K, Colborn T. Hypospadias and endocrine disruption: is there a connection? Environ Health Prospect. 2001;109(11):1175-1183.

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