EXTENDED SUMMARY
Introduction:
The Glans-Meatus-Shaft (GMS) Score is a pre-operative phenotypic scoring system used to assess hypospadias severity and risk for post-operative complications. The ‘M’ component is based on pre-operative meatal location, but meatal location sometimes changes after penile degloving, resulting in ‘meatal mismatch.’
Objective:
To identify: 1) the incidence and clinical predictors of meatal mismatch, and 2) the association of meatal mismatch with post-operative urethrocutaneous fistula development.
Study Design:
We performed a retrospective cohort study on patients who underwent primary hypospadias repair at a single center from 2011–2018. Meatal mismatch was defined as: upstaging (meatus moving more proximally after degloving), downstaging (moving more distally after degloving), or none. Covariates included: pre-degloving meatal location, chordee severity, penoscrotal anatomy, pre-operative testosterone, and number of stages for repair. To test the association between meatal mismatch and fistula development, we constructed two, nested, multivariable Cox proportional hazards regression models with and without meatal mismatch and compared them with the likelihood ratio test. A sensitivity analysis excluded patients with <6 months of follow-up.
Results:
Of 485 patients, 99 (20%) exhibited meatal mismatch, including 75 (15%) with upstaging and 24 (5%) patients with downstaging (Figure). Meatal mismatch was significantly associated with penoscrotal webbing, number of stages for repair, and pre-degloving meatal location, with downstaging being associated with more proximal meatal location. Over a median follow-up of 7.3 months (interquartile range 2.0–20.9), fistulae developed in 56 (12%) patients. On multivariable analysis, meatal upstaging was associated with a 3-fold increased risk of fistula development (Hazards Ratio [HR]: 3.04, 95% Confidence Interval [CI]: 1.44–6.45) compared to no mismatch. Meatal downstaging had similar risk of fistula development compared to no mismatch (HR: 0.99, 95% CI: 0.29–3.35). Multi-stage compared to single-stage repair was associated with reduced risk of fistula development (HR: 0.24, 95% CI: 0.09–0.66). The likelihood ratio test favored the model that included meatal mismatch. The sensitivity analysis showed similar findings.
Discussion:
Our short-term results suggest that meatal mismatch may be an important additional consideration to the GMS score as a tool to assess hypospadias severity, counsel families, and predict outcomes. Longer-term studies are needed to enhance the precision of risk stratification in hypospadias.
Conclusions:
Meatal mismatch occurred in 20% of patients undergoing hypospadias repair. Among this cohort, meatal upstaging was associated with a 3-fold increased risk of post-operative urethrocutaneous fistula development.
Keywords: hypospadias, urethrocutaneous fistula, GMS score, risk stratification
Introduction
In hypospadias repair, meatal location is the most commonly used variable by which surgical outcomes are stratified. However, other factors including glans and urethral plate characteristics, chordee severity, and type of repair also influence outcomes.1–10 Recognizing the need for a simple and reliable measure of hypospadias severity that incorporates more parameters than meatal location, Merriman et al. developed and validated the Glans-Meatus-Shaft (GMS) score in 2013.11 The GMS score is a phenotypic scoring system comprised of three separate components: G) glans and urethral plate quality, M) pre-degloving meatal location, and S) shaft curvature. Higher GMS scores have been associated with increased risk for post-operative complications.11,12
The inter-rater validity and reliability of the GMS score and its positive association with post-operative outcomes make it a valuable tool to facilitate standardized comparison of data between institutions and to track the success of variations in operative technique. However, the ‘M’ component of the GMS score is based on pre-operative meatal location.11 Surgeon observation in the operating room has revealed that meatal location often can change after penile degloving, resulting in ‘meatal mismatch.’ For example, an initial midshaft meatal location can shift into a true penoscrotal location if there is severe penile chordee, which may affect surgical approach, staging, and counseling.
Given the frequency with which meatal location is used to stratify outcomes data and the specification for pre-degloving meatal location in the GMS score, we sought to evaluate whether meatal mismatch may be an important additional consideration when predicting outcomes. We aimed to identify: 1) the incidence and clinical predictors of meatal mismatch, and 2) the influence of meatal mismatch on urethrocutaneous fistula development. We hypothesized that meatal mismatch would be associated with more proximal meatal locations and more severe chordee, and that meatal locations becoming more proximal after degloving would be associated with increased incidence of urethrocutaneous fistula following primary hypospadias repair.
Materials and Methods
Study Design and Population
A retrospective cohort study was performed of a prospectively-maintained database of patients who underwent primary hypospadias repair from 2011–2018 at a single, pediatric, large-volume, free-standing, tertiary referral center. Patients who did not undergo penile degloving (e.g., had glansplasty only), had no follow-up (i.e., never returned after surgical repair), had not yet undergone urethroplasty (i.e., only completed a 1st stage chordee correction), or had an incomplete medical record (e.g., missing operative details) were excluded. Institutional Review Board Approval was obtained (#2018–2197).
For each patient, intra-operative details including meatal location, chordee severity as measured by visual estimation after artificial erection, and other technical details were collected via a prospectively-recorded intra-operative case report form. A combination of the case report form and the electronic medical record were used to collect additional variables including: race, ethnicity, gestational age at birth, age at primary hypospadias repair, number of stages of repair, pre- and post-degloving meatal location, length of follow-up from final stage of repair, descriptors of penoscrotal anatomy, prescription of pre-operative testosterone, and development of post-operative urethrocutaneous fistula.
Outcomes and Exposures
For the first analysis, the primary outcome of meatal mismatch and its association with various clinical predictors were assessed. Meatal mismatch was defined as discordance between pre- and post-degloving meatal location, i.e., if the categorization of their pre-penile degloving meatal location did not match the categorization of their post-degloving meatal location. Meatal locations were stratified into glanular, coronal, distal/midshaft, and proximal to align with the categorizations used in the GMS score.11 Any meatal location proximal to the midshaft of the penis was considered proximal. Meatal mismatch was inclusive of both meatal downstaging (i.e., meatal location moving more distal after degloving) and meatal upstaging (i.e., meatal location moving more proximal after degloving), resulting in three meatal mismatch categories: meatal downstaging, no mismatch, and meatal upstaging.
For the second analysis, development of post-operative urethrocutaneous fistula and its association with meatal mismatch were assessed. Date of fistula development was defined as the earlier of either a clinic note detailing the date of fistula diagnosis or the re-operative date if clinic note was unavailable. The primary exposure of interest was meatal mismatch as defined in the three categories above.
Sensitivity Analysis
A sensitivity analysis was performed for the outcome of post-operative fistula development after restricting our cohort to patients who had ≥6 months of follow-up.
Statistical Analysis
Categorical variables were compared using the Chi-square or Fisher’s exact test. Continuous variables were compared using the Mann-Whitney U-test or Kruskal-Wallis test.
Odds of urethrocutaneous fistula development were evaluated with multivariable analyses. Variables that were significant on bivariate analysis with fistula development or that were a priori thought to be significant predictors of fistula development based on the literature were included into the multivariable model. We constructed two, nested, multivariable Cox proportional hazards regression models to adjust for differential follow-up for fistula development. The base model included GMS pre-degloving meatal location, chordee severity, pre-operative testosterone, and number of stages for repair. The full model included those same variables plus meatal mismatch. The likelihood ratio test was used to determine which model (base versus full) had a better fit. Cox proportional hazards assumptions were checked and verified for both models. The same methods were used in the sensitivity analysis.
All statistical analyses were performed with Stata version 14 (StataCorp, College Station, TX) with significance set at p<0.05. No adjustment was made for multiple comparisons.
Results
Study Population
Of 558 patients identified who underwent primary hypospadias repair, 485 (87%) met inclusion criteria. Patients were excluded due to lack of follow-up (n=35), lack of urethroplasty (n=23), no degloving (n=9), or an incomplete medical record (n=6). Table 1 shows cohort characteristics. Most patients were white (66%) and non-Hispanic (85%). Most patients (86%) underwent a single-stage repair, and the median age at initial repair (either single-stage or first-stage of a multi-stage procedure) was 9.6 months (range: 5.3–180.9; interquartile range [IQR]: 8.1–13.0 months). The median length of follow-up for the entire cohort from time of the latest stage surgery (i.e., urethroplasty) was 7.3 months (range: 0.1–90.0 months; IQR: 2.0–20.9).
Table 1.
Cohort characteristics overall and by meatal mismatch category.
| Total N=485, (%) | Meatal Mismatch Category | P-Value | |||
|---|---|---|---|---|---|
| Meatal Downstaging N=24, (%) | No Mismatch N=386, (%) | Meatal Upstaging N=75, (%) | |||
|
Median age at first surgery (Range, months) |
9.6 months (5.3–180.9) |
12.7 months (6.9–101.0) |
9.7 months (5.3–180.9) |
9.5 months (6.0–39.5) |
0.093 |
| Multi-stage | 70 (14) | 2 (8) | 49 (13) | 19 (25) | |
|
Median length of follow-up from latest stage surgery (Range, months) |
7.3 months (0.1–90.0) |
7.2 months (0.1–74.6) |
7.2 months (0.1–90.0) |
10.6 months (0.3–76.1) |
0.122 |
| Proximal | 89 (18) | 16 (67) | 73 (19) | 0 (0) | |
| Unknown* | 28 (6) | 1 (4) | 20 (5) | 7 (9) | |
| Buried Penis | 39 (8) | 2 (8) | 28 (7) | 9 (12) | 0.383 |
| Unknown | 1 (0) | 0 (0) | 0 (0) | 1 (1) | |
“Not documented” or “Unknown” category not included in Fisher’s exact test
Incidence of Meatal Mismatch
Pre-degloving meatal locations were classified as glanular (41/485, 8%), coronal (111/485, 23%), distal/midshaft (244/485, 50%), or proximal (89/485, 18%) (Figure 1). Ninety-nine patients (20%) exhibited meatal mismatch, including 24 patients (5%) with meatal downstaging and 75 (15%) patients with meatal upstaging.
Figure 1.
Meatal location agreement pre- and post-degloving, stratified into 4 locations by “M” score. Color code (for meatal location after degloving, compared to before): Dark Gray=meatal upstaging, White=no mismatch, Light Gray=meatal downstaging.
Clinical Predictors of Meatal Mismatch
There were no significant associations between meatal mismatch and race, ethnicity, or term-status. Pre-degloving meatal location, penoscrotal webbing, and number of stages for repair were each significantly associated with meatal mismatch on bivariate analysis, while chordee severity was not significantly associated with meatal mismatch (Table 1). Meatal upstaging was associated with more distal pre-degloving meatal location and multi-stage repair, while meatal downstaging was associated with more proximal pre-degloving meatal locations.
Development of Urethrocutaneous Fistulae
Urethrocutaneous fistulae developed in 56/485 patients (12%) at a median 7.3 months (range: 0.5–55.2 months; IQR: 1.8–14.6 months) after the last stage of the patients’ primary repair. Of the 56 patients who developed a fistula, 46 (82%) had undergone surgical repair by the time of study completion.
Bivariate analysis revealed that GMS pre-degloving meatal locations, prescription of pre-operative testosterone, and meatal mismatch were associated with increased risk of fistula development (Table 2). Chordee severity and number of stages for repair were not significantly associated with fistula development on bivariate analysis.
Table 2.
Bivariate Analysis of Risk of Urethrocutaneous Fistula Development, (%) reported by row.
| Total, N=485 | Fistula, N=56 | No Fistula, N=429 | P-Value | |
|---|---|---|---|---|
| Proximal | 89 | 14 (16) | 75 (84) | |
| Unknown* | 28 | 5 (18) | 23 (82) | |
| Buried Penis | 39 | 6 (15) | 33 (85) | 0.432 |
| Unknown | 1 | 0 (0) | 1 (100) | |
| Multi-stage | 70 | 7 (10) | 63 (90) | |
| Meatal upstaging | 75 | 15 (20) | 60 (80) |
“Unknown” category for chordee severity not included in Fisher’s exact test
In a multivariable Cox regression analysis (Table 3) incorporating GMS pre-degloving meatal location, chordee severity, stages of repair, and pre-operative testosterone (“base model”), multi-stage repair was significantly associated with 72% lower risk of fistula development (hazards ratio [HR]: 0.28, 95% confidence interval [CI]: 0.10–0.75). After additionally incorporating meatal mismatch into the model (“full model”), patients with meatal upstaging were significantly more likely to develop fistulae (HR: 3.04, 95% CI: 1.44–6.45) compared to those without any mismatch. Meatal downstaging had no significant influence on the incidence of fistulae in the full model (HR: 0.99, 95% CI: 0.29–3.35) compared to those without any mismatch. The association between pre-degloving proximal meatal location and fistulae development became significant, as patients with pre-degloving proximal meatal locations were significantly more likely to develop fistulae (HR: 6.28, 95% CI: 1.09–36.26). Multi-stage repair remained associated with a significantly reduced risk of fistula development (HR: 0.24, 95% CI: 0.09–0.66) in the full model. The likelihood ratio test demonstrated that the full model had a significantly better fit than the base model.
Table 3.
Multivariable Cox regression models with and without meatal mismatch (N=485). Likelihood ratio test showed better fit with full model (p=0.02).
| Variable | Base Model HR (95% CI), p-value | Full Model HR (95% CI), p-value |
|---|---|---|
| Proximal | 2.91 (0.60–14.03), p=0.18 | 6.28 (1.09–36.26), p=0.04 |
| Severe (≥61 degrees) | 5.39 (0.67–43.23), p=0.11 | 5.08 (0.63–40.58), p=0.13 |
| Multi-stage | 0.28 (0.10–0.75), p=0.01 | 0.24 (0.09–0.66), p=0.006 |
| Yes | 1.65 (0.92–2.98), p=0.10 | 1.43 (0.78–2.62), p=0.25 |
| Meatal upstaging | - | 3.04 (1.44–6.45), p=0.004 |
In the sensitivity analysis, 275 patients had ≥6 months of follow-up. Multivariable-adjusted estimates of risk of fistula development were similar to the primary analyses (Supplemental Table). Meatal upstaging, proximal pre-degloving meatal locations, and single-stage repair remained significantly and independently associated with higher risk of fistula development. The likelihood ratio test remained significant favoring the full model.
Discussion
Although meatal mismatch may often be recognized clinically, it has not been formally described or studied in previous hypospadias literature.13 In this study, we describe meatal mismatch in hypospadias and quantify its incidence, its clinical predictors, and its association with urethrocutaneous fistula development after surgical repair. Meatal mismatch occurred in 20% of patients, and, as expected, distal pre-degloving meatal location was associated with significantly increased risk for meatal upstaging, since proximal meatal locations cannot further upstage. Meatal upstaging was associated with a more than 3-fold increased adjusted risk for post-operative urethrocutaneous fistula development compared to no mismatch.
Reported rates of post-operative complications vary significantly based on meatal location; proximal repairs are associated with significantly higher rates of post-operative complications than distal repairs.14–18 Urethrocutaneous fistula is the most common complication associated with both distal and proximal repairs.14,18 Eleven percent of patients in this study with pre-degloving distal or midshaft hypospadias developed fistulae, higher than the 5.7% reported by a meta-analysis of 49 studies with variable lengths of follow-up but similar to a fistula rate reported in a randomized control trial analyzing suture types in distal repairs.14,19 Additionally, 16% of patients in this study with pre-degloving proximal hypospadias developed urethrocutaneous fistulae, which was lower than the 20–57% reported in four recent studies of patients with proximal hypospadias but with median durations of follow-up substantially longer than that in the present study.16–18 The disparities between our incidence of fistulae and the incidence of fistulae in other studies may be attributed to our short length of follow-up.
Aside from meatal location, other factors have been shown to be associated with development of post-operative complications, including small glans size8, poor urethral plate quality20, chordee requiring plication21, and single-stage repair of proximal hypospadias.18 Our results corroborate that multi-stage repair is associated with lower rates of fistulae than single-stage repair, even after multivariable adjustment for other a priori risk factors such as pre-degloving meatal location, chordee severity, and receipt of pre-operative testosterone. In addition, we found that meatal upstaging was an independent risk factor associated with fistula development. The association found between meatal upstaging and fistula development suggests that meatal upstaging should be an additional factor to be considered in the complex web of intra-operative decision-making. For instance, if a patient has a pre-degloving midshaft meatus that upstages to a more proximal location after degloving, our results suggest that a single-stage repair compared to a multi-stage repair may be associated with higher risk of fistula development postoperatively.
Part of the value of the GMS score is that it is assessed pre-operatively - a distinguishing feature from other hypospadias phenotypic scoring systems.11,22,23 Because it is assessed pre-operatively, the GMS score can effectively quantify patients’ hypospadias severity overall and according to several individual, important parameters. This helps surgeons with surgical planning and pre-operative counseling with families. Additionally, because the GMS score is easy to assess and has high inter-rater reliability, it can facilitate the sharing and comparison of more standardized data across institutions.11 These attributes of the GMS score, ideally, help surgeons evaluate the effectiveness of various surgical techniques on similar groups of patients, as results can be stratified according to individual and composite GMS scores.
Given the benefits of the GMS score outlined above, we do not seek to change the GMS score itself. Instead, we believe that meatal mismatch should be reported alongside the GMS score in future outcomes studies, or that an updated intra-operative GMS score should be developed. Higher composite GMS scores have been associated with increased risk of post-operative complications, including development of urethrocutaneous fistulae.11,12 While Arlen et al. also found that the individual ‘S’ component of the GMS score was associated with fistula development on multivariate analysis, they did not find that the individual ‘M’ component had a significant association with fistula development.12 Our results differ in that we found the individual ‘M’ component to be significantly associated with increased risk of fistula development, but only after incorporating meatal mismatch into the multivariate model. Given this finding, and that meatal upstaging is associated with fistula development, our results suggest that meatal mismatch should be further explored and considered in future hypospadias repair outcome studies.
In addition, we believe pre-operative counseling with families may be bolstered by discussing risk factors for meatal mismatch. While the GMS score can provide a valuable baseline estimate of post-operative risk, we have found that meatal upstaging is associated with increased risk for fistula development compared to no meatal mismatch. Though not statistically significant, a possible underpowered bivariate association was found between more severe chordee and meatal downstaging. The association could reflect severe chordee “hiding” a more distal meatal location that appears only after penile degloving. By discussing risk factors for meatal upstaging such as pre-operative meatal location, stages for repair, and penoscrotal webbing, families may have a fuller understanding of patients’ post-operative complication risk.
Our study has several limitations. First, our study population had a short median duration of follow-up (7.3 months). While follow-up was not important for the analysis of meatal mismatch (as the primary outcome took place on the day of surgery), it likely affects our analysis of urethrocutaneous fistula development, given recent evidence suggesting that fistula may take years to develop.24 It is likely that fistula rates may be higher if these patients had longer follow-up, which is why a sensitivity analysis was conducted of only those patients with ≥6 months of follow-up. Our results, however, remained unchanged. Secondly, due to the retrospective nature of the study, it is possible that some of the clinical characteristics studied, including mismatch between pre- and post-degloving meatal locations, were not always documented. Although the operative reports were consistently very detailed and the prospectively-recorded intra-operative case report form was updated to include all studied anatomical variables later in the study period, some information may have been omitted and affected our analysis, such as quality of urethral plate. We also only focused on fistula as the main outcome for this study. Third, we did not stratify our results based on type of repair (e.g., tubularized incised plate versus Thiersch-Duplay) beyond classification of single-versus multi-stage. While type of repair may influence development of urethrocutaneous fistula, we wished to focus this study on the utility of the “M” component of the GMS score in assessing risk for post-operative fistula development. While we do not have required data to calculate a full GMS score, meatal mismatch will change the overall score by ≥1 point, with direction depending on whether the mismatch was upstaging or downstaging. Finally, we could not assess how intra-operative decision-making was altered by presence of meatal mismatch. For example, we do not know how many patients might have originally been planned to undergo single-stage repair which was changed to a multi-stage repair after meatal upstaging was found.
Conclusions
Our results demonstrate that meatal mismatch occurs in 20% of patients with hypospadias, and that pre-degloving meatal location, penoscrotal webbing, and number of stages of repair influenced probability of meatal mismatch. Additionally, we found that meatal upstaging was associated with increased risk of fistula development, despite adjustment for other known risk factors. Only after accounting for meatal mismatch was the ‘M’ component of the GMS score significantly associated with development of urethrocutaneous fistula. Future studies are needed on enhancing precision of phenotypic scores for risk stratification in hypospadias repair surgery.
Supplementary Material
Funding
Anthony D’Oro was supported by the Crile Research Fellowship from Case Western Reserve University School of Medicine (CWRU SOM).
Dr. Chu was supported by K23 DK125670 from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)/National Institutes of Health (NIH).
The NIH, NIDDK, and CWRU SOM had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript. The views expressed in this article are those of the authors and do not necessarily represent the official view of the NIH, NIDDK, nor CWRU SOM.
Footnotes
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Conflict of Interest Statement
The authors of this study report no conflicts of interest.
Ethical Approval
This study was approved by the Institutional Review Board (#2018–2197).
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