Hypospadias has been recognized to be a common congenital malformation in Pediatric Urology. Children with hypospadias generally show ectopic position of the urethral orifice, chordee of penis and scarf-like changes in the dorsal foreskin of the penis (1). It is a highly heterogeneous multifactorial disease, which may be attributed to multiple genetic and environmental factors (2). Hypospadias is commonly treated by surgery to restore its appearance and function. It can be corrected at any age, without significant difference in the risk of complications, functional recovery and cosmetic effect. However, correction at an earlier stage is recommended by most researchers (3). At present, there are many corrective operations for hypospadias, yet accompanied by relatively higher incidence of postoperative complications. The major surgical complications are postoperative urinary fistula, urethral stricture, and unsatisfactory appearance, with the highest rate of urinary fistula in particular (4). Therefore, great concern in the treatment of hypospadias has been attached to the exploration of appropriate approaches to reduce the surgical complications.

The construction of abundant tissue barriers between the newly established urethra and the skin is the key to the surgery for hypospadias, which can reduce the occurrence of postoperative urinary fistula and promote the healthy formation of the newly formed urethra (5).

With the continuous development of science and technology, initial success has been realized in the application of microscopy for the repair of hypospadias. Through microscopic operation, the direction of blood vessels can be clearly visualized to ensure good blood supply of the covered tissue, leading to an improved success rate of surgery and hence reduced incidence of postoperative complications (6). With respect to the above, this study explored the combination of multilayer fascial tissue coverage tissue to cover the new urethra and microsurgery to improve the surgery for hypospadias, so as to reduce the occurrence of postoperative complications, which are reported as follows:

A total of 80 children were enrolled in this study, with 40 assigned to the study group and 40 to the control group. Children in the study group were aged between 4 and 11 years old (with an average of 7.20 ± 1.92), and tHOSE in the control group aged between 4 and 10 years old (with an average age of 6.90 ± 1.69). There was no significant difference in the comparison of general data between the two groups (p > 0.05), suggesting the comparability between groups (Table 1).

As shown in Table 2, there were statistically significant differences that the operation time (p = 0.03) was longer while the postoperative length of stay in the hospital (p = 0.000) was shorter in the study group than those in the control group. However, there was no statistical difference in the comparison of the amount of intraoperative bleeding between the study group and the control group (p = 0.112).

According to the comparison of surgical effect between the two groups in Table 3, the effective rate of the study group was 97.50%, while that of the control group was 82.50%. There was statistically significant difference that the effective rate of the former group was obviously higher than that of the latter group (p = 0.025).

In Table 4, the incidence of surgical complications was 7.50% in the study group and 25.00% in the control group 3 months after operation, with a significantly lower rate in the former group than that in the latter group (p = 0.034). Meanwhile, there was statistically significant difference that the HOSE score of the study group was significantly higher than that of the control group (p = 0.000).

There was no significant difference in indicators such as Q_max, Q_avc and PVR between the two groups before surgery (p > 0.05). While the levels of Q_max and Q_avc in the study group were higher than those in the control group 6 months after surgery, with statistically significant difference (p = 0.000). However, no significant difference was found in postoperative level of PVR between the two groups (p = 0.699), (Table 5).

Hypospadias is a common congenital malformation of the genitourinary tract in male children, accounting for 0.3%–0.5% of newborn boys, and still has an increased incidence recently (10). Among them, distal penile hypospadias accounts for about 70% of all cases of hypospadias (11). As a multifactorial disease, hypospadias may occur owing to the impact of heredity factors, environmental factors, hormone regulation, gene mutations, etc. Considering its complex etiology and pathogenesis, the exact cause of hypospadias can be clarified in only less than 5% of male children (12). Surgery is still the current gold standard for hypospadias (13). The most common complications of surgery for hypospadias are urinary fistula, urethral stricture and unsatisfactory appearance, which brings great psychological pressure to the affected male children and heavy economic burden to their families (14).

Urinary leakage has been estimated to have the highest incidence among all postoperative complications of surgery for hypospadias. Most male children may need to undergo secondary operation or multiple operations owing to the presence of urinary fistula (15). Urinary fistula is generally developed due to the weakness of tissues covering the newly formed urethra or poor blood supply (8), distal urethral obstruction and postoperative infection. Therefore, the innovation and modification of tissue-covering technology has been highly valued for the improvement of surgery for hypospadias in recent decades (16). The tissues to cover the newly established urethra of hypospadias mainly include subcutaneous sarcolemma of penis, tunica vaginalis of testis, Buck's fascia, external spermatic fascia, tunica dartos of the scrotum, etc. (17). For example, Daboos et al. (18) carried out a research based on a random grouping of hypospadias patients into multilayer coverage and no coverage groups. Corresponding results revealed that multilayer coverage could effectively reduce the postoperative complications, especially urinary fistula. It can be considered that coverage of the newly established urethra with multilayer tissue flap can not only reduce the tension of the newly formed urethra, avoid suture overlapping, but also enhance local anti-infection. Meanwhile, by enrolling patients undergoing TIP surgery, Savanelli et al. (19) randomly established two groups of ventral subcutaneous flap coverage group and no coverage group. Consequently, the incidence of urinary fistula in the coverage group was significantly reduced than that in the no coverage group. In addition, according to the report by Mammo et al. (13), the effect of sheath coverage for distal hypospadias was worse than that of vascular pedicle coverage, suggesting the application of double-layer vascular pedicle to cover the newly formed urethra. Moreover, Mammo et al. (13) believed that the newly formed urethra of distal hypospadias was far away from the scrotum, and hence the desired effect was difficult to achieve when there was an excessive stretching of the tissue as it could cause poor tissue blood circulation. Therefore, for the initial treatment of distal hypospadias, it is recommended to cover the newly formed urethra with proximal tissues such as penis sarcolemma, rather than distal tissues (e.g., the tunica vaginalis of testis, tunica dartos of the scrotum, etc.).

Microscopic technology is generally employed under the microscope. Via this approach, tissues and blood vessels can be magnified in the corresponding multiple under the field of vision to provide a clearer surgical field, which can ensure the accuracy of surgery. The technical concept of microsurgery is proposed to ensure the success of operation, which includes fine operation, protection of blood vessels and nerves, adequate protection of normal tissues, and non-invasive suture (20). The key to the success in the surgery for hypospadias is the achievement of tension-free and satisfactory suture of the new urethral lumen. Especially for children with relatively narrow urethral plates, microsurgery has achieved satisfactory anatomical separation of skin flaps, suture of newly formed urethral lumens and coverings under the magnified surgical field by using more sophisticated surgical instruments, thus reducing the occurrence of postoperative complications (21). Significantly, microsurgery for hypospadias has obvious advantages. To be specific, it can reduce the side injury of blood vessels and skin tissues as much as possible, and better protect the blood supply of the pedicled urethral plate flap. Moreover, the anatomical layers of tissues can be clearly distinguished during the shaping and dissociation of skin flaps under microscope to avoid postoperative edema of tissues and urethra, ischemia and necrosis of skin flap, etc. In addition, the use of fine sutures and small suture needles under the microscope for precise suture and smooth anastomotic alignment can accelerate wound healing, smooth wound surface and reduce the risk of stenosis of the newly established urethral lumen, which can eventually reduce postoperative complications and accelerate postoperative healing (22). Besides, as suggested by El-Karamany et al. (23), the application of microsurgery can also reduce postoperative pain, short the length of stay in the hospital and dressing change time, and decrease the incidence of postoperative complications for patients with distal hypospadias.

Furthermore, urethral stricture, second only to urethral fistula, is also one of the common complications after urethroplasty for hypospadias. According to previous report, the incidence of urethral stricture was 10%–20% after surgery for hypospadias (24), which occurred usually at the proximal and distal urethral anastomosis and the distal urethral duct 1–6 months after surgery. Therefore, early identification of urethral stricture and timely treatment are crucial for postoperative recovery and long-term effect of male children (25). Measurement of urinary flow rate is simple and non-invasive to detect urethral stricture (26). Abnormal urinary flow has been considered to have an inevitable relationship with urethral stricture to some extent (27). Abnormal urinary flow is an early warning of the risk of urethral stricture in 50% of cases after surgery for hypospadias. It highlights the necessity of preoperative and postoperative urinary flow measurement. Among them, Q_max is a simple and effective choice to evaluate urethral stricture (28). There is a reason to suspect urethral stricture when there is a reduced urinary flow rate.

In the present study, the hospital stay of the study group was significantly shorter than that of the control group, which may be related to the minimal trauma of microsurgery and faster postoperative recovery, suggesting that this surgical approach has advantages in accelerating recovery. The effective rate in the study group and the control group was 97.50% and 82.50%, respectively, with statistically significant difference between groups (p = 0.025). Meanwhile, comparison of the incidence of surgical complications showed statistically significant difference between the study group (6%) and the control group (20%) 3 months after operation (p = 0.034). The HOSE score in the study group was significantly higher than that in the control group, with a statistically significant difference (p = 0.000). Besides, statistically significant difference was also observed that the levels of Q_max and Q_avc in the study group were higher than those in the control group 6 months after operation (p = 0.000).

To sum up, microsurgery combined with covering new urethra by multilayer fascial tissue coverage tissues has some significance in preventing postoperative complications in male children with hypospadias. It exhibits more significant therapeutic effect, which is manifested in the shorter length of hospital stay, lower incidence of postoperative complications, and significantly improved urodynamic indicators. Findings in our study support the potential clinical application value of this approach in the surgical treatment of male children with hypospadias.

Our study still has some limitation, such as the experimental design of single-center study that may have certain selection bias. The follow-up period of this study was relatively short (6 months), which failed to fully evaluate long-term complications and the sustainability of urodynamic improvements. Future studies will extend the follow-up to 24 months and set multiple time points to assess the therapeutic effects. Our study failed to establish a control group of microsurgery combined with covering new urethra by single-layer sarcolemma tissues. In the future, there is a need for multi-center standardized clinical research based on a larger sample size, so as to objectively evaluate the advantages and disadvantages of this surgical strategy.