Various improvements in the details of UCF repair, including Y-V advanced skin flap pasty, tunica vaginalis flap and longitudinal relaxing incision, all aim to achieve tension-free closure, multilayer covering with hyper-vascularized tissue, and correction of distal obstruction [7–9]. However, UCF recurrence remains a challenge, and it is difficult to designate any technique as ideal or perfect. Numerous factors, such as UCF characteristics, meatal stenosis, local tissue conditions surrounding the fistula, details of the initial urethroplasty, and the surgical skills of the surgeon, are believed to be associated with the development of UCF recurrence [4, 5]. The incidence of UCF recurrence has been reported to be approximately 20% in previous studies [2–6]. Consistent with these findings, the UCF recurrence rate in our study was 22.8% (31/136). However, it is noteworthy noting that Snodgrass reported in a prospective study that the fistula recurrence rate was only 5% (2/37) which may be attributed to his excellent surgical skills [10].
Preoperative general health status and a history of suboptimal health may induce immunosuppression and increase morbidity after surgery. Fortunately, in our study, BMI at fistulectomy, history of low birth weight and prematurity did not increase the risk of UCF recurrence. Similar to findings by Dokter, who reported that common preoperative illness not severe enough to postpone surgery appeared to have a protective effect after hypospadias repair [11], suggesting that the success rate of UCF repair might be more dependent on the condition of the penis itself.
The condition during primary HR, such as defect in urethra length and the approach of urethroplasty, might affect the success rate of UCF repair, as different complication rates arise from different types of urethroplasty [5]. In our previous study, we observed that preserving the urethral plate or transecting it resulted in different UCF rates: 6.2% (59/949) and 3.2% (14/437), respectively [12]. However, in this further study, we found that preserving the urethral plate or not, as well as the length of the neourethra, did not affect the outcome of UCF repair. It may indicate that once the neourethra has survived, local lesions of the neourethra do not depend on the initial surgery but rather on the characteristics of the UCF itself.
Six months is recognized as the time required for skin vascularization and scar tissue softening. Therefore, all UCF repairs were performed at least 6 months after urethroplasty. Han reported that this interval was not a risk factor for failed UCF repair after transvers preputial island flap urethroplasty, which was consistent with our results (P = 0.037) [4]. Based on this, we conclude that 6 months is long enough for UCF repair, regardless of the approach adopted for primary urethroplasty. Although almost all UCFs occurred around one month after primary urethroplasty and were diagnosed within the first year after surgery, delayed presentation of UCFs was not rare [13]. The longest time to presentation of delayed UCF was 15.2 years, as reported by Johnston et al. [14]. In our study, 2% (3/136) of patients presented more than 1 year after HR. It is generally believed that delayed presentation of UCF after HR may be due to chronic urethral changes with age leading to unobvious obstruction or infection, while early presentation of UCF is mostly caused by ischemia, overlying lines, etc. To understand the influence of time on the outcome of UCF repair, we included patients’ age at UCF repair and the interval between HR and UCF presentation in univariate analysis. The results showed that the interval between HR and UCF presentation differed significantly between the success and recurrence groups. However, in the multivariate analysis, this interval was not a risk factor related to the recurrence of UCFs (P = 0.606). Therefore, we believe that late presentation and age at UCF repair would not affect the outcome of UCF repair.
Concomitant meatal stenosis is another risk factor for causing UCF, primarily through a mechanism of elevated pressures in the neourethra. Increased urethral pressure may lead to UCF recurrence. However, defining UCFs associated with meatal stenosis is challenging. Therefore, we combined the symptomatic presentation of patients with the intraoperative evaluation of the surgeon to diagnose meatal stenosis. Furthermore, a meatus that may be sufficient for a younger child may not suffice later in life. In this study, five patients were diagnosed with meatal stenosis, and the results mirrored previous reports indicating that once the meatoplasty was conducted simultaneously, it was not a risk factor of UCF recurrence [15].
Coronal fistula has long been regarded as a challenging issue in clinical management due to the lack of surrounding tissues. Although the location of the UCF was not consistently identified as a risk factor for failed UCF repair in some research [5, 16], we still consider it crucial to investigate in this study. Upon analyzing the data, we observed that the occurrence rate of coronal UCF was significantly higher than that of non-coronal UCF in both the univariate and multivariate analyses. Size and number were identified as the other two critical risk factors. The size of UCF was generally accepted as an independent risk factor correlated with failed UCF repair. The previously reported cut-off value of UCF diameter was 2mm [4, 10, 17]. Fan and colleagues concluded that classical fistulectomy was appropriated for coronal UCF with diameter < 2mm and 2-<4mm. For patients with coronal UCF combined with glans dehiscence or a coronal UCF with a diameter > 4mm, TIP or Mathieu urethroplasty was recommended. Classical fistulectomy applies to non-coronal UCF of all sizes [17]. Referencing this literature, we categorized the UCFs into three distinct groups according to the size of their diameters for analysis. The results of binary regression analysis revealed a significant difference among the groups. Specifically, UCFs with a diameter exceeding 4mm exhibited a higher recurrence rate compared to those with a diameter less than 2mm.These findings underscore the undeniable significance of the intrinsic characteristics of UCF in the success of UCF repair procedure.
Buck’s fascia was used as an integral covering in various urethroplasty for several years, with a certain effect on reducing the incidence of UCF. A multicenter retrospective study, including our institution, showed that out of 1386 patients who underwent one-stage urethroplasty, the incidence of UCF was 5.2% (73/1368), much lower than in other studies [12]. Successful repair of UCF depends on the inherent vitality of the neourethral tissue and the health of the local environment surrounding the fistula. Surgical proficiency and techniques employed in urethroplasty are also recognized as significant factors that could potentially influence the outcome [4]. Considering that 70 patients underwent primary urethroplasty combined with Buck’s fascia coverage, we added this factor in this study. As anticipated, both univariate and binary regression analyses corroborated that this factor is significantly associated with a reduced risk of UCF recurrence. We speculate that with the use of Buck’s fascia coverage during HR not only restores the continuity of the urethral spongiosum but also optimizes the stratification of urethral coverage to more closely resemble the normal anatomical structure. Furthermore, during the process of UCF repair, there was a more sufficient coverage of the fistula orifice with the dartos fascia contributes to a more robust healing process.
Limitation
The present study has several limitations that warrant acknowledgment. First, the stringent exclusion criteria may have resulted in the exclusion of potentially valuable cases, including patients with associated glans dehiscence. Second, we did not employ uroflowmetry, a measure that could have provided insights into the degree of urethral patency post repair. Third, the potential impact of postoperative infection on outcomes was not addressed within this study. Additionally, while our follow-up period was sufficient to detect most UCF recurrences, Hadley's report suggests that a small subset of patients (only 5.5%) with recurrent UCF present symptoms more than 1 year post repair[18]. This suggests that there is a possibility that some cases of late-presenting recurrent UCF were not captured in our study. Consequently, a long-term follow-up study is recommended to provide a more comprehensive understanding of late recurrences.