Nomogram-based prediction of postoperative complications in patients with hypospadias after perididymis covering
Introduction
Hypospadias is a prevalent pediatric urological condition characterized by disruption of anterior urethral development and ectopic deformity of the urethral orifice. It is often accompanied by a shortened and smaller penis, abnormal prepuce coverage, and penile curvature (1). This condition not only causes reproductive dysfunction but also significantly impacts the physical and mental development and overall health of affected individuals (2). Currently, surgery is the primary therapeutic method for the radical treatment of hypospadias, with over 200 surgical techniques reported (3).
The prepuce, with its abundant blood supply and elasticity, provides effective coverage for the newly formed urethra. It is commonly utilized in tubularized incised plate urethroplasty (TIP) and transverse preputial island flap urethroplasty (Duckett) and is a common surgical approach for hypospadias treatment (4). However, due to the different anatomical structures of the urethral plate in patients with hypospadias, the repair methods are relatively complex, and there is no surgical method suitable for various types of hypospadias in clinical practice. This complexity contributes to a high incidence of postoperative complications and suboptimal prognoses (5).
Perididymis covering is a method to free perididymis and cover the formed anterior urethral wall to strengthen the anterior urethral wall tissue in order to reduce the incidence of complications such as urethral fistula and urethral diverticulum after urethroplasty. Identifying the factors influencing postoperative complications of perididymis covering in patients with hypospadias is essential for developing targeted treatments. This approach aims to reduce postoperative complications and improve the prognosis of patients. Accordingly, this study investigates the risk factors for postoperative complications of perididymis covering in patients with hypospadias. We present this article in accordance with the TRIPOD reporting checklist (available at https://tp.amegroups.com/article/view/10.21037/tp-24-368/rc).
Methods
General data
A total of 204 patients with hypospadias who underwent perididymis covering at the hospital between May 2018 and May 2024 were enrolled into the present study. The patients were aged between 1 and 10 years, with an average age of 3.27±0.68 years, and had a body mass index ranging from 28 to 22 kg/m2, with an average body mass index of 20.59±1.64 kg/m2. Hypospadias was categorized as distal in 90 cases, intermediate in 62 cases, and proximal in 52 cases (6). Preoperative conditions included 74 cases of penile curvature, 54 cases of scrotum dysplasia, and 41 cases of testicles dysplasia.
Surgical interventions consisted of 104 cases using the TIP and 100 cases using the Duckett method. The distribution of surgeries across seasons was 54 cases in spring, 52 cases in summer, 50 cases in autumn, and 48 cases in winter. Analgesic cleaning modes (refers to cleansing during surgical anesthesia) were categorized as 112 cases in the earlier stage and 92 cases in the later stage. The vascular distribution of the prepuce is very clear during the operation, and the surgeon can define the vascular distribution of the prepuce according to clinical observation. The vascular distribution of the prepuce was noted as single branch in 91 cases and multiple branches in 113 cases. Regarding the number of surgeries, there were 82 cases of one-stage surgery and 59 cases of multiple-stage surgery. Informed consent was obtained from the legal guardians of all patients.
This study was conducted in accordance with the declaration of Helsinki (as revised in 2013) and approved by the Ethics Committee of Tangshan Maternal and Child Health Center (No. 2021-046-01). Written informed consent was obtained from the legal guardians of participants.
Inclusion and exclusion criteria
Inclusion criteria were as follows: (I) patients who met the diagnostic criteria for hypospadias (6); (II) patients under 18 years of age; (III) patients who met the surgical indications for perididymis covering (it is indicated for all kinds of urethroplasty, and is not indicated if there is a preoperative history of bilateral cryptorchid surgery, absence of testicular sheaths or damaged testicular sheaths); (IV) patients who underwent either the TIP or Duckett procedure; (V) patients who had one-stage surgery or multiple-stage surgery performed by the same surgeon; and (VI) patients with normal coagulation and immune function.
Exclusion criteria were: (I) patients who also had other urological diseases; (II) patients with hermaphroditism; (III) patients with significant diseases affecting the heart, liver, kidneys, or other vital organs; (IV) patients with other chronic underlying diseases; (V) patients who refused follow-up visits; (VI) patients with a previous history of urethroplasty; and (VII) patients with malignant tumors.
Study methods
Baseline data collection
Baseline data included age, body mass index, length of the formed urethra (distal, intermediate, proximal), presence of preoperative penile curvature (yes, no), preoperative scrotum dysplasia (yes, no), preoperative testicles dysplasia (yes, no), surgical methods (TIP, Duckett), surgical season (spring, summer, autumn, winter), operation time, intraoperative blood loss, analgesic clean mode (earlier stage, later stage), prepuce vascular distribution (single, multiple), and number of surgeries (one-stage, multiple-stage), preputial covering (such as full covering, partial covering, full exposure).
Statistical analysis
Data processing was conducted using SPSS 25.0 software. The Shapiro-Wilk normal distribution was used to test the normality of the measurement data. Data conforming to a normal distribution were represented as mean ± standard deviation, with comparisons between groups performed using the independent samples t-test. The measurement data conforming to skewed distribution were expressed by [M (P25, P75)], and the Mann-Whitney U test was used for comparison between groups. Categorical data were expressed as n (%), and the Chi-squared test was utilized for comparisons.
Binary logistic regression analysis was used to analyze the relationship between various factors and postoperative complications of perididymis covering in patients with hypospadias. R software (R4.1.0) and the rms package were used to develop a nomogram model for predicting these complications. The receiver operating characteristic (ROC) curve was adopted, and the area under the curve (AUC) was calculated to determine the predictive value of the nomogram model (test level α=0.05).
Results
Postoperative complications and grouping
After 1 year of follow-up, postoperative complications of perididymis covering in patients with hypospadias were assessed according to relevant consensus criteria (6). Among the 204 patients, complications were observed in 63 cases (30.88%): 10 cases of wound infection (15.87%), 22 cases of urinary fistula (34.92%), 14 cases of urethral stenosis (22.22%), 4 cases of urethral diverticulum (6.35%), and 13 cases of residual penile curvature (20.63%). The remaining 141 patients (69.12%) did not experience complications.
Comparison of baseline data between the two groups
The complication group exhibited higher age and longer formed urethra compared to the non-complication group. Additionally, the complication group had higher proportions of intermediate and proximal hypospadias, preoperative penile curvature, utilization of the Duckett surgical method, and surgeries performed in summer (P<0.05) (see Table 1).
Table 1
| Items | Complication group (n=63) | Non-complication group (n=141) | t/χ2/F/U | P |
|---|---|---|---|---|
| Age (years) | 5 [5, 6] | 5 [4, 5] | 5.387 | <0.001 |
| Body mass index (kg/m2) | 20.64±1.76 | 20.58±1.58 | 0.242 | 0.81 |
| Length of the formed urethra (cm) | 2.01±0.28 | 1.72±0.25 | 7.372 | <0.001 |
| Types of hypospadias | 13.527 | 0.001 | ||
| Distal | 17 (26.98) | 73 (51.77) | ||
| Intermediate | 21 (33.33) | 41 (29.08) | ||
| Proximal | 25 (39.68) | 27 (19.15) | ||
| Preoperative penile curvature | 8.312 | 0.004 | ||
| Yes | 32 (50.79) | 42 (29.79) | ||
| No | 31 (49.21) | 99 (70.21) | ||
| Preoperative scrotum dysplasia | 0.054 | 0.82 | ||
| Yes | 16 (25.40) | 38 (26.95) | ||
| No | 47 (74.60) | 103 (73.05) | ||
| Preoperative testicles dysplasia | 0.016 | 0.90 | ||
| Yes | 13 (20.63) | 28 (19.86) | ||
| No | 50 (79.37) | 113 (80.14) | ||
| Surgical methods | 11.359 | <0.001 | ||
| TIP | 21 (33.33) | 83 (58.87) | ||
| Duckett | 42 (66.67) | 58 (41.13) | ||
| Surgical seasons | 15.230 | 0.002 | ||
| Spring | 15 (23.81) | 39 (27.66) | ||
| Summer | 27 (42.86) | 25 (17.73) | ||
| Autumn | 10 (15.87) | 40 (28.37) | ||
| Winter | 11 (17.46) | 37 (26.24) | ||
| Operation time (minutes) | 82.31±6.08 | 81.42±6.21 | 0.952 | 0.34 |
| Intraoperative blood loss (mL) | 43.25±5.52 | 44.13±5.23 | 1.091 | 0.28 |
| Analgesic clean mode | 0.032 | 0.86 | ||
| Earlier stage | 34 (53.97) | 78 (55.32) | ||
| Later stage | 29 (46.03) | 63 (44.68) | ||
| Prepuce vascular distribution | 0.411 | 0.52 | ||
| Single | 26 (41.27) | 65 (46.10) | ||
| Multiple | 37 (58.73) | 76 (53.90) | ||
| Number of surgeries | 0.010 | 0.92 | ||
| One-stage | 25 (39.68) | 57 (40.43) | ||
| Multiple-stage | 38 (60.32) | 84 (59.57) | ||
| Preputial covering | 11.028 | 0.001 | ||
| Full covering | 11 (17.46) | 31 (21.99) | ||
| Partial covering | 31 (49.21) | 99 (70.21) | ||
| Full exposure | 21 (33.33) | 11 (7.80) |
Data are presented as median [range], mean ± standard deviation, or n (%).
Relationship between various factors and the occurrence of postoperative complications
The postoperative complications of perididymis covering in patients with hypospadias were analyzed using the status variable (1= “complication”, 0= “no complication”). Independent variables included age, length of the formed urethra, types of hypospadias, preoperative penile curvature, surgical methods, and surgical seasons (variable assignment listed in Table 2). Binary logistic regression analysis identified age, length of the formed urethra, types of hypospadias, preoperative penile curvature, and surgical methods as risk factors for postoperative complications [odds ratio (OR) >1, P<0.05] (see Table 3).
Table 2
| Relevant factors | Variables | Assignments |
|---|---|---|
| Age | Continuous variables | – |
| Length of the formed urethra | Continuous variables | – |
| Types of hypospadias | Categorical variables | 2= “proximal”, 1= “intermediate”, 0= “distal” |
| Preoperative penile curvature | Categorical variables | 1= “yes”, 0= “no” |
| Surgical methods | Categorical variables | 1= “Duckett”, 0= “TIP” |
| Surgical seasons | Categorical variables | 3= “summer”, 2= “winter”, 1= “autumn”, 0= “spring” |
Table 3
| Influencing factors | B | SE | Wald | P | OR | 95% CI |
|---|---|---|---|---|---|---|
| Age | 1.833 | 0.387 | 22.425 | <0.001 | 6.253 | 2.928–13.353 |
| Length of the formed urethra | 5.141 | 0.953 | 29.073 | <0.001 | 170.870 | 26.369–1,107.234 |
| Types of hypospadias | 1.047 | 0.274 | 14.595 | <0.001 | 2.849 | 1.665–4.874 |
| Preoperative penile curvature | 0.964 | 0.435 | 4.905 | 0.03 | 2.622 | 1.117–6.152 |
| Surgical methods | 1.228 | 0.446 | 7.583 | 0.006 | 3.416 | 1.425–8.188 |
| Surgical seasons | 0.226 | 0.190 | 1.416 | 0.23 | 1.254 | 0.864–1.819 |
| Constant | −21.948 | 3.252 | 45.546 | <0.001 | – | – |
SE, standard error; OR, odds ratio; CI, confidence interval.
Construction of a nomogram prediction model
A nomogram prediction model for postoperative complications of perididymis covering in patients with hypospadias was constructed based on age, length of the formed urethra, types of hypospadias, preoperative penile curvature, and surgical methods (see Figure 1). Bootstrap was used to verify the nomogram model of secondary infection. The results showed that the C-index value was 0.906, indicating that the model had good discrimination, and the calibration curves fit well with the ideal curve (see Figure 2). The ROC curve was plotted for internal verification of the nomogram model, and the results showed an AUC of 0.909 [95% confidence interval (CI): 0.866–0.952], indicating significant predictive values, with a sensitivity of 0.746, a specificity of 0.929, and a Youden’s index of 0.675 (see Figure 3).
Discussion
Relevant studies indicate a gradual increase in the incidence of postoperative complications following perididymis covering in patients with hypospadias. As of 2008, the incidence was reported to be as high as 30%. The results of this study showed a similar incidence rate of 30.88%. Urinary fistula and urethral stenosis are the most common types of postoperative complications, accounting for about 14% of related complications, which seriously affects the postoperative daily life of patients with hypospadias (7). Therefore, identifying predictive factors for these complications is crucial for providing targeted treatment, reducing complication rates, and improving patient prognosis.
Binary logistic regression analysis identified age, length of the formed urethra, types of hypospadias, preoperative penile curvature, and surgical methods as risk factors for postoperative complications. Younger patients, due to their rapid growth and robust tissue regeneration, benefit from early surgery, which prolongs scar softening and absorption time and enhances the flushing effect of urine flow on the urethral wall, facilitating the restoration of normal penile function and reducing the occurrence of curvature (8,9). Additionally, younger patients have a relatively short penis, the length of newly formed urethra is hence shorter, and less tissue is required, resulting in less damage to the body and an improved prognosis (10). In contrast, older patients are more likely to develop wound infections due to mature puberty and increased urethral discharge (11). In addition, postoperative fibrous cords tend to limit penile development, resulting in poor prognosis (12).
The findings of Hensle et al. support these observations, showing that older age at the time of surgery correlates with worse surgical outcomes and a higher incidence of postoperative complications (13). Therefore, early screening and timely surgical intervention for patients with hypospadias, when feasible, are recommended to effectively reduce the risk of postoperative complications.
The length of the formed urethra is related to the length of the urethral defect. Patients with hypospadias who have longer urethral defects often experience insufficient vascular pedicle protection during perididymis covering. This insufficiency can lead to inadequate blood supply during urethral reconstruction, which adversely affects flap healing and leads to poor urethral tension. Consequently, this condition can cause postoperative complications such as urinary fistula and infection (14). Additionally, the longer length of the constructed urethra may result in an inadequate width of the surgical flap and increased suture tension (15). Patients are prone to postoperative urethral spasms, thereby resulting in urethral stenosis which then affects prognosis (16).
Furthermore, the thinness of the newly constructed urethra in cases of long defects can cause retraction of the skin tube, leaving the anterior urethral orifice at the penis head uncovered. The lack of laxity at the inversion of the skin tube may cause distortion and infection of the formed urethra, thereby resulting in a series of complications.
Hypospadias is categorized into distal, intermediate, and proximal types (17). The results of this study showed a higher incidence of complications in patients with proximal hypospadias and penile curvature compared to other types. Previous studies have highlighted that both the presence and degree of penile curvature are crucial factors in determining the appropriate surgical procedure (18). Clinically, for patients with proximal hypospadias and penile curvature, the urethral plate must be incised to correct the curvature. If this measure is insufficient, dorsal folding may be required during surgery, increasing its complexity and consequently the risk of postoperative complications (19).
In addition, the closer the urethral orifice is to the proximal end, the more pronounced the penile curvature. After correction, the external urethral orifice is positioned farther from the penis head, resulting in a longer urethral defect (20). The increased length of the reconstructed formed urethra required in the surgery complicates ensuring adequate blood supply, thereby increasing the risk of postoperative complications (21).
The TIP and Duckett procedures are both widely used surgical procedures for the clinical treatment of hypospadias. The key to TIP is to open the urethral plate without grafting, so as to wrap it around the stent tube to create a new urethral tube. This technique preserves the intact urethral plate and makes the urethral orifice resemble a normal structure, thereby reducing postoperative complications (22). The Duckett procedure is commonly used in moderate to severe hypospadias, which uses the junction of the inner and outer plates of the prepuce to create a skin tube with a vascular pedicle thereby enhancing the survival rate of the newly formed urethra (23). However, the Duckett operation is more complex, requiring extensive experience and high precision from the surgeon. Inadequate tissue coverage following Duckett urethral reconstruction can lead to insufficient blood supply and distal obstruction, resulting in complications such as urinary fistula and urethral stenosis.
Existing literature indicates that urethral fistula is the most common postoperative complication of perididymis covering (24). Inadequate tissue coverage of the new urethra or insufficient blood supply of the flap are recognized as primary causes of postoperative urethral fistula, which is consistent with the results of this study (25). Therefore, selecting the most appropriate surgical method based on the severity and type of hypospadias is essential in clinical practice to minimize the incidence of postoperative complications (26).
In this study, the regression analysis model was visualized and graphically processed by constructing a nomogram model, enabling intuitive and convenient prediction of postoperative complications of perididymis covering in patients with hypospadias. Moreover, the model demonstrated good discrimination and practicability without requiring complex operations. In clinical practice, this nomogram model can be widely used to identify high-risk patients early and implement effective treatment measures targeting high-risk factors, thereby preventing postoperative complications and improving patient prognosis.
However, there are some limitations in this study, such as a single-center small-sample study with a subjective selection of surgical methods, short follow-up time, and insufficient data collection, which may introduce selection bias. Other influencing factors were not included in the study. Future research should expand the sample size and adopt a multi-center prospective study design to include more potential influencing factors, further validating the nomogram model for predicting postoperative complications in patients with hypospadias to obtain more accurate results.
Conclusions
In conclusion, age, length of the formed urethra, types of hypospadias, preoperative penile curvature, and surgical methods are closely related to the incidence of postoperative complications following perididymis covering in patients with hypospadias. Clinically, relevant treatment plans can be formulated based on these indicators to reduce the occurrence of postoperative complications in patients.
Acknowledgments
Funding: This study was supported by
Footnote
Reporting Checklist: The authors have completed the TRIPOD reporting checklist. Available at https://tp.amegroups.com/article/view/10.21037/tp-24-368/rc
Data Sharing Statement: Available at https://tp.amegroups.com/article/view/10.21037/tp-24-368/dss
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Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tp.amegroups.com/article/view/10.21037/tp-24-368/coif). The authors have no conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the declaration of Helsinki (as revised in 2013) and approved by the Ethics Committee of Tangshan Maternal and Child Health Center (No. 2021-046-01). Written informed consent was obtained from the legal guardians of participants.
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