At present, people pay more and more attention to the treatment of DSD patients. In the past, the urethroplasty among patients with DSD and severe hypospadias was perceived the same way since the treatment was mainly for the repair of hypospadias in DSD patients. In recent years, people gradually realized that DSD patients who underwent urethroplasty were a unique subgroup of hypospadias patients that needed to be studied and analyzed separately [6]. Previous studies on proximal hypospadias had shown that the factors affecting the success rate of proximal hypospadias are operative age, suture selection, bleeding control, urine drainage, postoperative infection and so on. This study mainly focused on the main complications of urethroplasty in patients with DSD, such as urethral fistula, urethral stricture, and urethral diverticulum. On the basis of the influencing factors of severe hypospadias, the possible influencing factors were expanded and analyzed based on the characteristics of DSD.

The study found that the factors related to the success rate of operation were the length of urethral defect (P = 0.026 < 0.05) and the method of operation (P = 0.019 < 0.05).

According to the results, we conducted a separate analysis of the factors influencing the three most common surgical complications that require reoperation:

The formation of urethral diverticulum could be the result of many factors. After studying urethral diverticulum and various factors, it concluded that the staged operation was related (P = 0.003 < 0.05) but had nothing to do with the length of urethral defect.

The results of this study showed that the staged surgery could decreased the occurrence of urethral diverticulum. The flatness of the foreskin and the stability of the rebuilt urethra during the one-stage operation were worse than the staged surgery since the formed part of the urethra was more stable with urethral plate prepared in the first stage. In the staged surgery, the surgeons directly formed the residual defect of the urethra with the Duplay operation during second-stage surgery, which makes the newly-built urethra more stable than the one-stage operation. It reduced the possibility of urethral diverticulum formation due to the less vortex flow in the urine because of more stable urethra [7].

It wasn’t found that there was obvious correlation between the length of urethral defect and the generation of urethral diverticulum. Liu Xin and her team found that the risk of urethral diverticulum would increase by 2.54 times if the length of the primary urethroplasty increased by one centimetre [8]. It also suggested that patients with defective urethral length above 3.35 cm were more likely to develop urethral diverticulum. However, the correlation was not found in this study.

Previous reports on factors affecting urethrocutaneous fistula often included the type of hypospadia, the age of operation, the width of the urethral plate, and various elements of the urethroplasty [9]. Building on the existing data, we did partial verification and found that the occurrence of urethrocutaneous fistula was related to the age of the first operation (P = 0.006 < 0.05), the length of urethral defect (P = 0.001 < 0.05), and TPIT-related operation (P = 0.000 < 0.05). The evidence suggests no correlation with the type of hypospadia, the time of urethral stent, and the coverage with a protective layer.

The data showed the incidence rate of the urethrocutaneous fistula elevated as the urethra defect increased. It was analyzed that the longer the defective urethra was, the more urethral repair materials were needed, and the greater the aspect ratio of the skin flap was used to repair the urethra. Thus, a longer urethral defect made it difficult to ensure a sufficient blood supply, bringing hardship to the growth of the flap and the healing of the anastomosis. What’s more, a longer reconstructed urethra produced more anastomoses during the operation, resulting in more complications such as urethrocutaneous fistula [10]. Regarding the age of first operation, additional analysis was carried on the relationship between the age of first operation and the length of urethral defect. The two had a significant correlation (P = 0.006 < 0.05) while the P-value of logistic regression between age and urethrocutaneous fistula was 0.161 > 0.05. Although the age of the first operation was related to the occurrence of postoperative urethral fistula, it was not an independent factor. In the studies [11,12,13] on the related factors of urethrocutaneous fistula after hypospadias, the influence of the age of the first operation on the effect of operation was differed. Some people thought that the older the age of operation, the greater the possibility of postoperative complications, especially for urethrocutaneous fistula [14]. However, several experts thought that operation age on the effect of operation was not significant within a certain age range. It suggested the success rate of operation decreased with the increase of age before a certain age. Therefore, it was possible that the influence of operation age existed, but with certain limitation.

In addition, this study also found that TPIT-related surgery was beneficial for the occurrence of urethrocutaneous fistula. TPIT was not accepted by surgeons because of its complex operation and long learning curve. TPIT required higher blood supply of skin flap because of its circular anastomosis and island flap, so the possibility of urethrocutaneous fistula after operation should be higher. However, the actual result was different from the assumption. The primary surgery was mainly TPIT and Koyanagi. There was one longitudinal anastomosis line attached to the cavernosum of the penis and the coverage of the urethral anastomosis was paid attention to in the TPIT procedure. However, there were two longitudinal anastomosis lines, one of which was not covered by anything in the Koyanagi operation. Because of that, the occurrence rate of postoperative urethrocutaneous fistula in Koyanagi was higher. In the staged procedure, the second stage of Byars staged surgery was urethroplasty while the second stage of staging TPIT surgery was the repair of urethrocutaneous fistula. The length of the urethral anastomosis in staged TPIT surgery was much shorter than Byars staged surgery, lowering the possibility of postoperative urethrocutaneous.

It must be mentioned that the study of the relationship between the surgical success rate and staged surgery suggested that there was a significant correlation between the two. However, in the correlation study between urethrocutaneous fistula and staged surgery, it was found that there was no significant correlation. Although staged surgery increased the success rate of surgery, it didn’t reduce the incidence of postoperative urethrocutaneous fistula. In theory, staged surgery ensured the blood supply of the newly-built urethra which leading to further reduce the occurrence of urethrocutaneous fistula, but an analysis of the two showed no correlation—staged surgery didn’t reduce the occurrence of urethrocutaneous fistula. It was believed that the influence wasn’t obvious that staged surgery brought in the blood supply of the newly-built urethra. The major problem resulting in urethrocutaneous fistula was the blood supply of anastomoses.

It wasn’t found that the urethrocutaneous fistula was related to the covering layer of the reconstructed urethra, different from several previous article [9, 15]. It suggested a lower possibility of urethrocutaneous fistula occurred if the testicular sheath covered the urethra, following by scrotal sarcoid coverage and subcutaneous fascia coverage in these articles. In this study, the correlation P-value between the two is 0.061, closer to P < 0.05. According to the rate of postoperative urethrocutaneous fistula, the possibility of urethrocutaneous fistula with the urethra covered by the scrotal sarcoid was less than that covered by the subcutaneous fascia, both better than without any coverage. Different results may be obtained if the sample size was further expanded.

The correlation analysis of the occurrence of urethrocutaneous fistula and the use of hormones came to a result of P = 0.059 (relatively close to P < 0.05). Previous reports had also suggested that the use of hormones can promote blood supply to the skin flaps, hence reducing the occurrence of postoperative urethrocutaneous fistula [16]. The sample size could be further expanded to verify whether the two are related.

In the study, it came to the conclusion that there was no relationship between urethral stricture and all factors.

Urethral stricture was one of the common complications after urethroplasty, which usually occurred within 6 months after operation, even for a longer time such as in sexual development or adulthood [17]. The follow-up time of all cases in this study was more than 1 year. However, all cases had not been followed up until sexual development, so the study lacks a certain degree of rigor. As for the influence of surgical methods on urethral stricture, experts believed that urethral stricture after urethroplasty often occurs in urethroplasty with pedicled skin flap or free tissue coiled tube, because there was a circular anastomosis in this kind of operation [6, 7]. Circular scar contracture was easy to occur at the anastomotic site, leading to urethral stricture. However, no correlation between surgical methods and urethral stricture was found in this study. It had to be noted that all urethral strictures in this study occurred in TPIT-related procedures, and there were 91 cases of TPIT-related operations in this study, accounting for 82.7% of the total cases. Therefore, the deviation in the number of cases may affect the statistical results. In future studies, we needed to further balance the number of cases between the two groups, and further statistical analysis might lead to different results.