Tubularized incised plate urethroplasty for distal hypospadias: A literature review

The tubularized incised plate (TIP) urethroplasty or Snodgrass procedure has gained worldwide acceptance for distal hypospadias repair due to its low complication rate, good cosmetic result, and technical simplicity. As a result, several articles have been published concerning various aspects and subtle variations of this procedure. The aim of this review is to critically and systematically analyze the published complication rates of TIP repair for distal hypospadias in children. We also reviewed the surgical modifications that have been introduced to the original technique and discussed the potential impact on the final outcome of the Snodgrass procedure.


INTRODUCTION
The tubularized incised plate (TIP) repair is based on an old principle of urethral plate tubularization, also known as the Thiersch-Duplay procedure. [1,2] Although a good concept, its main drawback was the limitation imposed by the width of the urethral plate. Historically, if the urethral groove was not wide enough for tubularization in situ, alternative approaches such as the Mathieu urethroplasty (ß ip-ß ap technique) or a vascularized island flap were performed. [3][4][5][6][7][8][9] In 1994, Snodgrass popularized the concept of urethral plate incision with subsequent tubularization and secondary dorsal healing for primary hypospadias repair. [10] Not surprisingly, the principle of incising the urethral plate had been employed before, but for different purposes. [11,12] In 1987 Ordeszewski incised the plate to achieve easier tubularization in redo cases where the urethral plate is often scarred. [11] Two years later, Rich took advantage of hinging the plate in onlay island ß ap repairs in order to improve the conÞ guration of the meatus. [12] This relatively simple yet elegant and effective procedure has gained widespread acceptance since its description 13 years ago, currently being recognized as the surgical technique of choice for distal hypospadias, according to a recent survey of Pediatric Urologists. [13] In this article, we critically and systematically compared the complication rates of TIP repair for distal hypospadias in children. We also reviewed the surgical modiÞ cations that have been introduced to the original technique, commenting on how they have potentially affected the Þ nal outcome of the Snodgrass procedure.

Overall complication rate
The overall complication rate for the Snodgrass procedure ranged from 0 to 50%. The highest complication rate was found in a study that involved only two patients with distal hypospadias, aged 14 and 62 years. The older patient in this series developed a Þ stula explaining the high (50%) complication rate. [71] This study also described the experience with other techniques for hypospadias repair in adults and concluded that performing hypospadias surgery in older patients was associated with more complications. O'Connor also included three adults (oldest being 39 years of age) in his series, but did not discriminate the complications in this particular subgroup. [70] Likewise, Sharma reported on 13 adults aged 18-26 years of age who underwent TIP repair. Five of them had distal hypospadias and only one developed a Þ stula (20%). [65] The largest study addressing hypospadias in adults included 97 patients, but only 14 underwent TIP urethroplasty. The overall complication rate was 8.7%, but it was not possible to separate the complications involving only TIP repairs. [72] Therefore, even after combining data from these four studies, limitations attributable to the small sample size (n = 24) do not allow one to conclude that TIP repair has a higher complication rate in adults.
If we exclude these four articles that included adult patients,

*Study also involved redo hypospadias
Braga et al.: The use of TIP repair for distal hypospadias the overall complication rate of TIP urethroplasty goes down to 33%. Here again, some points are worth mentioning. If we exclude another eight studies (for reasons that will be explained below), the complication rate drops even further, reaching 23%. [3,5,44,54,64,[73][74][75] The high complication rates from the Thailand [75] (33%) and the Nairobi [74] (30%) studies may be explained by the lack of familiarity with the surgical technique as both articles described their initial experiences with the Snodgrass procedure. For instance, the Nairobi study was able to reduce their 76% complication rate using other techniques for hypospadias repair to 30% after adopting TIP urethroplasty. [74] Furthermore, four articles that reported high overall complication rates with TIP repair for distal hypospadias included primary and redo cases. [3,54,64,73] Similar results have been reported by other studies in the literature showing that redo hypospadias are associated with more complications. [22][23][24][25][26][27][28][29][30][31] Unfortunately, we could not determine the isolated complication rate for the primary cases based on the data provided. Therefore, what has been presented for those four studies was the combined complication rate for both primary and secondary hypospadias, explaining the high Þ gures.
In this setting, Snodgrass' own practice supports the importance of surgeon experience and case-load. When one analyzes only his results with distal hypospadias, his overall complication rate ranges from 0 to 7%. [10,67,85,87,90,[95][96][97][98][99] as seen in Table 5. The 7% Þ gure though was the result of a multicenter study involving Þ ve different centers across the United States and one in Europe, [96] not a single surgeon practice. If we only consider his single experience, the reported complication rate varies from 0 to 4%, mostly Þ stulas and very few meatal stenoses (approximately 2%).

Fistula rate
Of 54 studies reporting on occurrence of Þ stulas, the median Þ stula rate was 5.0% (mean = 5.9%), ranging from 0 to 16%. [3][4][5][6]10, The Hospital for Sick Children experience included 48 children who underwent TIP urethroplasty from 1996 to 2000, representing the early part of our experience with this technique. [94] The Þ stula rate was 4%, similar to the Þ gures summarized with this review. Several factors may inß uence Þ stula formation: surgical technique, delicate tissue handling, patient age, type of hypospadias defect, surgeon experience, waterproof urethroplasty coverage, and concomitant foreskin reconstruction, among others. [43] In this review, we have found Þ ve articles involving TIP repair associated with foreskin preservation. [73,80,97,100] In the largest series published on this topic, involving 149 children with distal hypospadias, Leclair et al. reported similar Þ stula rates for patients with and without prepuce preservation. [80] In contrast, our preliminary analysis suggests a higher Þ stula rate (14%) in children with foreskin preservation when compared to those cases where the foreskin was removed and a dartos ß ap was harvested and transferred ventrally. We speculate that this might have occurred due to lack of waterproof coverage (dartos ß ap) in children who had foreskin preservation. [101] Surgical principles are important, especially in hypospadias surgery. With that in mind, Snodgrass has recommended two-layer neourethra closure to decrease Þ stula formation in all types of hypospadias defects. [16] He has reported that his Þ stula rate reduced from 33 to 11% when performing two-layer urethroplasty in proximal hypospadias. Careful interpretation of his results has shown an unbalanced distribution of other technical factors (confounders) between the assembled groups which were not accounted for and might have affected the outcome. [16] Similarly Cheng et al. reported <1% complication rate for distal hypospadias in more than 400 patients in whom the urethroplasty was performed in two layers. [55] Despite these excellent results, no prospective comparative study involving one vs. two layers has been conducted to date. According to Snodgrass's experience, the Þ stula rate reduced to almost 0% when in addition to two-layer neourethra closure, the urethroplasty was covered with a tunica vaginalis ß ap instead of a dartos ß ap. [102] Age at operation has also been suggested to affect the outcome of hypospadias surgery. [103] Perlmutter et al. have reported on 194 boys who underwent TIP repair for distal hypospadias and concluded that the Þ stula rate was signiÞ cantly lower in children younger than 6 months vs.  Complication rate older patients (>6 months). [103] These Þ ndings support the current tendency of early hypospadias repair in children, normally between 6 and 18 months of age. [43]

Technical modifications
Most technical modiÞ cations of the Snodgrass technique have included different ways to harvest the dartos ß ap in order to cover the urethroplasty, not changes to the urethroplasty technique itself as summarized in Table 2. In this setting, the variations described include a local de-epithelialized skin ß ap, [47] a lateral skin ß ap, [48] or a ventral-based dartos ß ap. [50,51] One urethroplasty modiÞ cation was proposed by Jayanthi, when he suggested that the tubularization should be performed over a 10-or 12-Fr feeding tube and working from the meatus proximally. [49] Another surgical change was described by Kiss who decided to incise the urethral plate while performing a Mathieu type of repair [52] but, perhaps the most creative innovation has been the "Snodgraft" procedure which consists in covering the raw surface of the incised plate with an inlay preputial or buccal graft. Some authors have utilized this technique preferably for redo hypospadias, [30,53,104] but its application in primary cases has also been described. [63] In 1998, Kolon and Gonzales were the Þ rst to describe the use of dorsal inlay graft urethroplasty for redo cases. [53] Following them, Haynes and Malone in 1999 and then Schwentner and colleagues in 2006 applied the same technique for salvage hypospadias repair. [30,104] Recently, Asanuma et al. published on 28 children who underwent dorsal inlay graft urethroplasty for primary hypospadias (17 distal and 9 midshaft/proximal) and achieved good results with an acceptable Þ stula rate (3.6%). [63]

Comparative analysis between mathieu and snodgrass techniques
We were able to find seven studies in our literature review that compared the Snodgrass repair to the Mathieu technique [3][4][5][6][44][45][46] as shown in Table 1. Four of them reported fewer complications with the TIP repair. [3][4][5]44] Two studies showed no difference between the two procedures in regards to complications, but stated that the Snodgrass technique seemed to achieve better cosmetic results. [45,46] In the only prospective trial encountered in this review, Oswald et al. randomly allocated 30 children to undergo the Snodgrass operation and 30 to have the Mathieu procedure. The authors concluded that TIP repair was associated with lower complication rates vs. the Mathieu technique and that the cosmetic results were far more satisfactory with the TIP operation. [6] CONCLUSION We were able to identify only one prospective randomized study involving TIP repair for distal hypospadias in children. [6] Future efforts should be made to start prospective data collection and initiate randomized clinical trials involving hypospadias surgery. As with any review, clinical heterogeneity of the studies due to different geographic locations as well as singular demographic factors offered some limitations to the comparability of the data. Furthermore, confounders were not always accessible due to ambiguity in reporting among authors, who combined distal as well as proximal hypospadias and primary and redo cases. Both study variability and confounding factors may have affected the validity and therefore the generalizability of this review.
Thus far, TIP urethroplasty appears to be the best available procedure for correction of distal hypospadias in children. By using standard techniques cited in this review, the pediatric urologist can expect a predictable outcome with complications rates below 10%.