Glans–Urethral Meatus–Shaft (GMS) Scoring System in Hypospadias: A Multicontinental Systematic Review and Meta analysis

ABSTRACT

Background:

Traditional hypospadias classification systems based solely on meatal position inadequately predict surgical complexity and outcomes. The Glans–Urethral Meatus–Shaft (GMS) scoring system was developed to provide multidimensional phenotypic assessment, incorporating glans morphology, meatal location, and penile curvature.

Objective:

To systematically evaluate the clinical utility of GMS scoring in hypospadias assessment, prognostic counseling, and surgical outcome prediction through a comprehensive analysis of published evidence.

Materials and Methods:

A systematic review and meta-analysis were conducted following Preferred Reporting Items for Systematic Reviews and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Embase, Scopus, Ovid, and Google Scholar were systematically queried for studies reporting GMS scoring in unoperated hypospadias cases. Data extraction and quality assessment were performed independently by two reviewers. Statistical analysis employed random-effects models with 95% confidence intervals.

Results:

Twenty-seven studies encompassing 2300 unoperated hypospadias cases from 10 countries across the globe were included. Seventy-five percent of studies were published within the past 5 years. Studies demonstrated the following primary applications: Complication prediction (n = 19), surgical decision-making (n = 16), cosmetic outcome assessment (n = 10), validation studies (n = 10), artificial intelligence integration (n = 5), comparative scoring analysis (n = 12), and developmental research (n = 2). Statistical analysis revealed a significant association between increasing GMS severity and urethra-cutaneous fistula incidence (Z = 4.2871, P < 0.001).

Conclusions:

GMS scoring provides a validated, reproducible hypospadias severity assessment with demonstrated clinical utility in risk stratification, surgical planning, and outcome prediction. While showing strong correlation with surgical complications, weaker associations with cosmetic outcomes indicate the need for complementary assessment tools. Integration with emerging technologies and standardization of scoring methodology represent key priorities for optimizing clinical implementation.

INTRODUCTION

Hypospadias, affecting 1 in 200–300 male births globally, represents one of the most common congenital anomalies requiring surgical correction.[1] The complexity and phenotypic heterogeneity in hypospadias have challenged surgeons in optimizing treatment approaches and standardizing outcome assessment. Traditional classification systems, based predominantly on the position of the urethral meatus, have proven inadequate for capturing the multidimensional severity of hypospadias and predicting surgical outcomes.[2,3]

Historical systems by Duckett and Orkiszewski focused on meatal location relative to anatomical landmarks, failing to incorporate critical factors that influence surgical complexity, including glans morphology, urethral plate quality, and penile curvature.[4] This single-parameter approach proved insufficient for predicting complications or functional outcomes, creating significant gaps between anatomical classification and clinical utility.

The Glans-Urethral Meatus-Shaft (GMS) scoring system, introduced by DeCaro et al. and Merriman et al., addressed these limitations through multidimensional phenotypic characterization.[5,6] GMS integrates three anatomical components – glans size/urethral plate quality (G), meatal location (M), and penile curvature (S), each scored 1–4, generating total scores of 3–12.[7] Initial validation demonstrated excellent inter-observer reliability and significant correlation with postoperative complications.[6,8,9]

Despite expanding applications in surgical decision-making, risk stratification, and outcome prediction, the GMS literature remains heterogeneous, with predominantly single-center studies of variable methodology. Questions persist regarding the validity across various surgical approaches, the correlation with long-term outcomes, and the applicability across diverse populations. Recent developments include integration with artificial intelligence (AI) and associations with developmental biology, expanding potential utility beyond surgical classification.[10,11]

This systematic review and meta-analysis evaluate the GMS clinical utility, assessing reliability across settings, correlation with surgical outcomes, decision-making applications, emerging technologies integration, and limitations to provide evidence-based implementation recommendations.

MATERIALS AND METHODS

The review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.[12] The multidisciplinary review team comprised of pediatric surgeons, including pediatric urologists, urologists, computational biologists, research scientists, experts in biomedical informatics, biostatisticians-epidemiologists and experts in systematic review and meta-analysis. There were no conflicts of interest among the team members, and the study did not receive any external funding.

The study protocol, including the objective, search strategy, inclusion and exclusion criteria, and statistical methodologies, was outlined in advance. All crucial steps in the review process, including search-execution, data extraction, and data analysis, were performed in duplicate by two independent reviewers. Any discrepancies were resolved through consensus and referral to the original source in the presence of the senior author.

Search strategy

An existing systematic review on the same subject was excluded prior to undertaking the review. PubMed, PubMed Central, Scopus, Embase, Ovid, and Google Scholar were systematically interrogated using relevant search terms including “hypospadias,” “GMS score,” and “glans–urethral meatus–shaft” score. Missing publications were identified through reference and citation tracking. Published abstracts and conference proceedings were searched for subject to open access availability.

Inclusion and exclusion of studies

No restrictions pertaining to the year or language of publication, geographical region, or study design were imposed. The case reports, series, books, theses, animal studies, editorials, commentaries, and review articles were, however, excluded.

The search strategy and results have been outlined in the PRISMA flow diagram [Figure 1].

Figure 1.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow diagram

Data extraction and analysis

Data were extracted from the included studies into Excel spreadsheets (Microsoft Excel for Mac version 16.9.1) and collated. The methodological quality of each study was assessed in the Joanna Briggs Institute Critical Appraisal Checklist.[13] No studies were, however, excluded from the synthesis to incorporate diverse evidence in the analysis.

The single-arm analysis was performed in MedCalc® Statistical Software, version 20.106 (MedCalc Software Ltd., Ostend, Belgium; 2022). The analysis employed a random effects model and pooled analysis with estimation of a 95% confidence interval (CI). The funnel plot, Begg’s test and Egger’s test were used to estimate the publication bias. The geographical locations based on the continents of the published papers were illustrated with R software, version 4.4.1 (R Foundation for Statistical Computing, Vienna, Austria).

RESULTS

The study cohort comprised data pertaining to 2300 unoperated cases of hypospadias from 27 studies reported across 10 countries in 3 continents, namely Asia, North America, and Africa. The mean age of the participants was 2.70 ± 2.03 years (minimum, maximum: 0.73, 7.5 years). The studies were predominantly prospective (n = 15; 55.56%) or retrospective (n = 10; 37.04%) with minimal representation of cross-sectional (n = 1) and case–control (n = 1) studies. While all were single-centre studies, Arlen et al. and Kim et al. collected data from more than one institute.[7,14] Within the study cohort, 33.33% (9/27) of studies primarily or partially used photographs or image-based methods rather than real-time clinical examination.[14,15,16,17,18,19,20,21]

Three-fourths (21 of 27; 77.78%) of the studies have been published over the last 5 years. The maximum number of publications is from Asia (n = 15; 55.56%), followed by North America (n = 9; 33.33%) and Africa (n = 4; 14.81%) [Figure 2].

Figure 2.

Global distribution of published papers across the globe. The color gradient represents the number of published papers, with darker shades indicating higher counts and lighter shades representing fewer publications

The anatomic subtypes of hypospadias have been reported in 48.15% (13/27) of studies only. Distal penile (or mild) hypospadias was the most commonly reported anatomic subtype of hypospadias (60.97%; 714/1171) of the study cohort. This included coronal (n = 270/909), distal (n = 192/909), sub-coronal (n = 80/909), and glandular (n = 45/909) hypospadias in that order of prevalence. The mid-penile (moderate) hypospadias was present in 13.15% (154/1171) of the study cohort. Proximal (severe) hypospadias was represented by 25.8% (303/1171) cases and included proximal penile (n = 145/909), scrotal (n = 49/909), penoscrotal (n = 43/909) and perineal (n = 12/909) hypospadias (the exact location of the urethral meatus was not clear in 262 cases in the study cohort).

Urethra-cutaneous fistula (UCF) was the most common complication, occurring in approximately 11.44% of cases (183/1599). The other complications included meatal stenosis (4.95%), urethral diverticulum (4.52%), glans dehiscence (2.72%), wound dehiscence (2.42%), and phimosis (0.83%) [Table 1].

Table 1.

Pooled proportion of postoperative complications following hypospadias repair [heterogeneity, trend analysis, and publication bias assessment]

Type of Complication	Events	Sample size	Proportion (%)	95% CI	Weight (%)
					Fixed	Random
UCF	183	1599	11.45	9.93 – 13.11	33.67	15.12
Meatal stenosis	49	991	4.95	3.68 – 6.48	20.88	14.94
Glans dehiscence	23	847	2.72	1.73 – 4.05	17.85	14.87
Phimosis	3	362	0.83	0.17 – 2.40	7.64	14.19
Urethral stricture	43	512	8.4	6.15 – 11.15	10.8	14.53
Urethral diverticulum	14	310	4.52	2.49 – 7.46	6.54	14.01
Wound dehiscence	3	124	2.42	0.50 – 6.91	2.63	12.34
Total (fixed effects)	318	4745	6.18	5.51 – 6.90	100	100
Total (random effects)	318	4745	4.71	2.23 – 8.05	100	100

Test for heterogeneity
Q	126.42
DF	6
Significance level	P<0.0001
I2 (inconsistency)	95.25%
95% CI for I2	92.37 to 97.05
Publication bias
Egger’s test
Intercept	-7.019
95% CI	-18.6171 to 4.5792
Significance level	P=0.1805
Begg’s test
Kendall’s Tau	-0.3333
Significance level	P=0.2931

There was considerable heterogeneity in how the GMS score was operationalized and interpreted in studies comprising the study cohort. While the original intent of the score was to offer a quantitative metric for hypospadias severity, its use in the reviewed literature is more diverse. Seventeen studies treated GMS as a continuous variable in logistic regression, ROC curve, or correlation analyses, whereas eight studies applied categorical thresholds to define severity levels, most commonly using a cut-off of c10 to indicate “severe” hypospadias.[8,19,22] A few others used the alternate thresholds, such as a9[23] or defined severity using anatomic subtypes rather than absolute scores.[24]

Broadly speaking, 27 studies included in this review could be sub-stratified into several domains based upon their respective objectives and outcomes. The most dominant theme (n = 19 studies) involved using the GMS score as a predictor of short- and medium-term postsurgical complications such as UCF, glans dehiscence, and urethro-cutaneous breakdown.[5,6,7,8,15,16,18,21,22,23,24,25,26,27,28,29,30,31] The second theme (n = 10) focused on exploring GMS score in relation to cosmetic and subjective outcomes.[14,20,21,23,25,27,32,33,34,35] Sixteen studies used the GMS score to guide pre-operative risk stratification or surgical decision-making, such as choosing between one-stage and staged procedures.[5,8,15,16,19,21,22,23,24,26,27,28,29,31,34,36] Ten studies addressed the inter-observer reliability and validation of the GMS score, either alone or in comparison with other scoring systems like Hypospadias Objective Penile Evaluation (HOPE) or plate objective scoring tool (POST).[5,6,14,15,17,18,19,22,34] Five studies explored the integration of GMS scoring with AI, image segmentation or machine learning-based digital phenotyping.[14,15,17,19] Twelve studies compared GMS against other scoring systems, either by proposing new metrics like POST[18,19] or validating GMS against hypospadias objective scoring evaluation (HOSE),[21,23,25,35] HOPE,[14,33,34] and Pediatric penile perception score (PPPS) in various clinical settings.[20] Elmore and Maizels extended GMS into the Glans–Urethral Meatus–Shaft + Urethral plate (GUMS) via an e-learning platform.[15] Two studies examined GMS not merely as a surgical severity score but as a proxy for underlying developmental and tissue-level abnormalities.[16,36]

GMS score as a predictor of surgical complications (n = 19)

Higher GMS scores (total score or specific sub-components) were consistently associated with elevated rates of postoperative complications, including UCF, glans dehiscence, meatal stenosis, and urethral stricture formation.[6,7,8,19,22,29] Arlen et al. quantified this relationship, reporting that each one-point increase in the GMS score increased the odds of a complication by 1.44 times (95% CI: 1.24–1.68).[7] Shoukry et al. echoed this trend, citing a 3.23-fold rise in complication risk per unit increase in GMS score.[8] De Oro further demonstrated that opting for a staged repair significantly reduced the risk of UCF formation (HR: 0.28; 95% CI: 0.10–0.75) in anatomically severe cases.[28] Abbas et al., reported an area under the curve of 0.82, indicating good discriminatory ability for predicting surgical outcomes.[19]

Across all GMS categories, UCF was the most frequently reported complication.[37] While individual studies addressed complication rates across different levels of severity, most did not disaggregate outcomes by individual GMS subgroups (i.e., GMS 10, 11, 12).[23,26] However, the subgroup analysis using the Cochran–Armitage trend test revealed an upward trend in UCF incidence with increasing GMS scores (Z = 4.2871, P < 0.001), although the rise was more prominent between mild (GMS: 3–6) and moderate (GMS: 7–9) as compared to that between moderate and severe (GMS: 10–12) hypospadias [Table 1 inset picture].

Several studies further emphasized the prognostic utility of specific GMS components. For instance, glans width <14 mm or a proximally located meatus or degree of shaft curvature were associated with higher surgical failure and reoperation rates in studies.[25,27,32] Notably, Huang et al. found that complication rates increased significantly in patients with GMS 11 scores undergoing one-stage repairs, while GMS 12 showed the highest complication rate overall. These findings support the use of higher GMS scores as a clinically actionable threshold for surgical planning.[26]

Conversely, Indriasari et al. reported no significant association between GMS and complication rates.[20] The scoring criteria and applications of GMS varied across the study cohort, with some studies modifying the system or using it descriptively without analyzing its association with outcomes.[6,24,27,32]

GMS score and cosmetic outcomes

Ten studies explored the relationship between GMS score and cosmetic or parental satisfaction outcomes, using both subjective (PPPS) and objective (HOPE) assessment tools. Indriasari et al. found no correlation between GMS and postoperative PPPS scores,[20] while Kim et al. found modest to strong associations between specific GMS components (especially glans configuration and meatus type) and cosmetic appearance scores.[14] While GMS may offer some predictive value for aesthetic outcomes, it is likely influenced by other surgical and healing variables not captured by anatomical scoring alone.

GMS score in surgical decision-making (n = 16)

Studies have established the role of GMS as an important preoperative triage tool, enabling surgeons to stratify patients into pathways of repair and counselling. Maheshwari et al. and Shoukry et al. emphasized the value of GMS in predicting technical complexity and failure risk, thus justifying a staged approach in higher severity cases.[8,27] Karakaya et al. and Abdelhalim et al. demonstrated that GMS sub-components, such as a narrow urethral plate or small glans that could serve as guides for tailoring the surgical approach to individual patient anatomy.[32,36] Chandni et al., embedded the GMS score into a prospective, structured clinical protocol to guide comparative evaluation of surgical techniques.[21]

GMS score validation and interobserver reliability (n = 4)

Merriman et al. reported excellent interobserver agreement (kappa >0.7) across all three score components.[6] Elmore and Maizels introduced a variant scoring system (GUMS) and used a Computer Enhanced Visual Learning (CEVL) platform to demonstrate its educational and reliability potential.[15] Kim et al. conducted a large-scale photo-based expert validation study showing high agreement in meatal and shaft scoring, but noted moderate variability in glans and urethral plate evaluations.[14] These findings underscore the reproducibility of GMS when standardized visual criteria and training are applied, while also highlighting areas (like glans depth) where subjective interpretation may limit consistency.

Integration with AI, image analysis, and advanced tools (n = 5)

Fernandez et al. and Caldwell et al. used image segmentation and machine learning techniques to classify hypospadias anatomy and compare it with GMS, enabling more objective phenotyping and tissue assessment.[16,17] Kim et al. applied automated scoring to preoperative photographs from two institutions, demonstrating strong interobserver agreement in GMS and HOPE components using digital workflows.[14] Elmore and Maizels developed an e-learning module (CEVL) that used GMS-derived “GUMS” scoring to train clinicians in outcome prediction, supporting scalable digital standardization.[15] Abbas et al. introduced the POST tool, a quantifiable urethral plate scoring system and validated its superiority to GMS in predicting complications using digital imaging and software-based measurement tools.[19] Collectively, these innovations reinforce the role of GMS-based anatomy scoring as a cornerstone in developing automated, reproducible and scalable platforms for precision hypospadias surgery.

Comparative scoring systems and extensions of GMS (n = 12)

Comparative analyses across 12 studies critically examined the performance of the GMS score in relation to other established or novel hypospadias scoring systems, including HOSE, HOPE, POST, PPPS and GUMS. Abbas et al. introduced the POST to address the subjectivity inherent in evaluating urethral plate quality, a component not explicitly scored in the original GMS system. POST demonstrated superior inter-observer reliability (inter-class correlation [ICC] = 0.84) and stronger ICC compared to the “G” component of GMS, suggesting a more reproducible method for assessing plate-related severity.[18,19] The HOSE, which integrates both cosmetic and functional outcomes, was used postoperatively in four studies,[21,23,25,35] although it often showed a weak correlation with GMS-based severity. Similarly, the PPPS, a subjective measure completed by patients or caregivers, was employed in a study and showed minimal alignment with GMS components[20,38] [Table 2].

Table 2.

Comparison of hypospadias scoring systems

Scoring System	Developer/Year	Components Assessed	Scoring Method	Primary Application	Strengths
Traditional Anatomical Classification	Harrison and Smith et al. 1960, Baskin et al. 1998, Orkiszewski 2012	Meatal position only	Descriptive categories (anterior, middle, posterior)	Basic anatomical description	Simple, intuitive; widely understood; standard terminology
GMS (Glans–Meatus–Shaft)	DeCaro et al. 2012, Merriman et al. 2013	Glans size/urethral plate quality, meatal location, shaft curvature	1–4 scale per component (total 3–12)	Complication prediction, surgical planning, risk stratification	Excellent inter-observer reliability (κ >0.7); 1.44× risk per unit; multidimensional; validated; easy to apply
POST (Plate Objective Scoring Tool)	Abbas et al. 2020, Abbas et al. 2023	Urethral plate width, depth, quality	Objective digital measurement	Urethral plate assessment in distal hypospadias	Superior inter-observer reliability (ICC=0.84); addresses GMS limitations; digital integration
GUMS (Glans–Urethral Plate–Meatus–Shaft)	Elmore et al. 2015	Glans configuration, urethral plate, meatal position, shaft curvature	Modified GMS+urethral plate domain	Education, surgical training	More comprehensive than GMS; enhanced urethral plate evaluation; digital/educational utility
HOPE (Hypospadias Objective Penile Evaluation)	Neheman et al. 2022, Neheman et al. 2024, Kim et al. 2024	Meatal position and shape, glans shape, skin coverage	Objective cosmetic scoring	Postoperative cosmetic assessment	Focus on aesthetics; good inter-observer agreement; validated; patient-relevant
HOSE (Hypospadias Objective Scoring Evaluation)	Ali et al. 2020, Guler et al. 2020, Aydin et al. 2019, Chandni et al. 2023	Combined cosmetic and functional outcomes	Multi-domain scoring	Postoperative outcome evaluation	Integrates function and aesthetics; clinically relevant; broad coverage
PPPS (Penile Perception and Parents’ Perception Scale)	Indriasari et al. 2022	Subjective satisfaction (cosmetic + functional)	Patient/parent questionnaire	Patient-reported outcomes	Patient- and parent-centered; real-world insight; long-term relevance
AI-Enhanced Digital Systems	Fernandez et al. 2023, Caldwell et al. 2024, Kim et al. 2024, Elmore et al. 2015, Abbas et al. 2023	Variable: image segmentation, automated landmarks	Machine learning algorithms	Automated phenotyping and prediction	Objective; scalable; reduces bias; supports pattern recognition

Key Observations:

• GMS remains the most extensively studied and validated system

• POST systems offer superior objectivity but limited scope

• GUMS and HOSE attempt a multidimensional assessment but lack validation

• HOPE and PPPS focus on outcomes that matter to families

• AI-enhanced systems may address current limitations but need validation

Elmore and Maizels proposed a modification of the original GMS score by introducing the GUMS score, which adds urethral plate appearance as a fourth domain. This adaptation aimed to create a more anatomically comprehensive and reproducible classification system, particularly for use in surgical education platforms such as the CEVL module.[15] Collectively, these comparative studies validate the foundational utility of the GMS score while simultaneously highlighting its limitations, especially in assessing cosmetic outcomes and urethral plate anatomy. They underscore the growing interest in integrating GMS with more functionally nuanced or digitally calibrated frameworks to enhance its clinical and research applicability.

GMS score as a proxy for developmental and prenatal factors

Two studies have expanded the utility of GMS by exploring its potential as a phenotypic marker of underlying etiopathogenesis in hypospadias.[39] Abdelhalim et al. investigated the role of GMS score as a marker of the severity of embryologic disturbances during genital development. The study demonstrated a significant association between higher GMS scores and younger maternal age, as well as shorter anogenital distance, an established surrogate marker of disrupted fetal androgen exposure.[36] Complementing this, Fernandez et al. linked increasing GMS severity with histopathological evidence of inflammation and fibrosis within penile tissues, implying a possible biological continuum between anatomical severity and tissue-level alterations. Together, these findings suggest that the GMS score may serve not only as a surgical classification system but also as a proxy for developmental and molecular alterations in hypospadias pathophysiology.[16] Although currently limited to isolated studies, this emerging application highlights the potential of GMS as a research tool for exploring disease mechanisms and identifying at-risk populations. The funnel plot depicting no publication bias is represented in Table 1 (inset figure).

Preoperative–intraoperative variations and their impact on postoperative outcomes

Several studies reported clinically relevant variations between preoperative GMS assessment and intraoperative findings, particularly with respect to urethral plate quality, degree of chordee, glans configuration, and intraoperative meatal mismatch. These discrepancies influenced intraoperative decision-making and postoperative outcomes. D’Oro et al. demonstrated that intraoperative meatal mismatch, not always evident during preoperative assessment, was independently associated with an increased risk of UCF formation.[28] Other studies similarly noted that intraoperative reassessment of glans size and curvature frequently resulted in modification of the planned surgical approach, especially in patients with higher GMS scores, thereby impacting complication rates and the need for staged repair[8,22,26] [Figure 3].

Figure 3.

Glans, Meatus, and Shaft (GMS) scoring system and clinical domains. The figure illustrates the GMS scoring components, along with their severity grades, and summarizes key research domains and clinical outcomes associated with the GMS system in hypospadias

DISCUSSION

GMS scoring extends beyond pure anatomical classification to include functional, developmental, cosmetic, and patient-centered outcomes. Convergent evidence from 2300 cases across 27 studies supports that the GMS score is a multifaceted, versatile clinical framework that can transform the assessment of hypospadias from simple anatomical classification to comprehensive phenotypic characterization. GMS has the potential to provide risk quantification, enabling evidence-based surgical planning and family counseling.[40] Given the emotional and functional implications of hypospadias repair and complications thereof, the role of GMS in evidence-based shared decision-making regarding surgical timing and technique selection cannot be overemphasized. The consistent association between higher GMS scores and increased complication rates across diverse geographic and institutional settings validates its universal applicability.

The development of the GMS scoring system represents a paradigmatic shift from historical reliance on unidirectional approaches such as those proposed by Duckett and others, which suffered from the fundamental flaw of single-parameter-based assessment and failed to capture the multidimensional nature of the hypospadias phenotype. The conceptual foundation of GMS reflects the recognition that hypospadias severity should be understood as a constellation of three anatomical features formally integrated into a unified, reproducible scoring framework with demonstrated clinical utility.

The clinical utility of GMS extends beyond anatomic segregation of the malformation to active surgical planning, particularly in the challenging management of severe hypospadias. The evidence supporting staged approaches for higher GMS scores provides objective criteria for one of pediatric urology’s most subjective decisions.[7,41] The differential complication rates between single-stage and staged approaches across GMS severity levels offer evidence-based guidance for surgical technique selection.[26] The need to balance the technical complexity and risk of failure against the patient age, family preferences and institutional expertise represents GMS’s most impactful clinical utility, directly influencing operative planning, resource allocation and patient counseling.

The assessment of cosmetic and subjective outcomes, explored in 10 studies, represents another important dimension where GMS provides valuable insights,[14,20,21,23,25,27,32,33,34,35] though with acknowledged limitations in fully predicting patient and family satisfaction. Two studies reported that glans and meatus sub-scores of GMS had limited ability to predict cosmetic satisfaction, especially in adolescents and older children, highlighting the subjectivity of aesthetic perception.[14,33,34]

The successful integration of GMS with AI and machine learning demonstrated its adaptability to emerging technologies while comparative analyses with other scoring systems have helped define its relative strengths and limitations.[16,17] AI-enhanced scoring to reduce variability while maintaining clinical relevance is a promising trajectory towards more objective and reproducible assessment. For instance, the POST system developed by Abbas et al. for digitized urethral plate evaluation and Elmore’s and Maizels e-learning-based validation of the GUMS score illustrate how image-based platforms can enhance reproducibility, reduce interobserver variability and support remote training and clinical standardization.[15,19]

Perhaps the most novel insight was the emergence of GMS as a potential proxy for developmental and biological perturbations. Two studies explored associations between GMS and prenatal or histopathological variables.[16,36] GMS severity correlated with maternal age, anogenital distance and tissue-level inflammation or fibrosis, suggesting that the score may capture more than surface anatomy. If validated, such associations could position GMS as a non-invasive surrogate for prenatal androgen exposure or tissue remodeling dynamics. This hypothesis aligns with recent shifts in pediatric urology towards integrating phenotypic, molecular and genetic data. Although current evidence is limited, the correlation between anatomic severity and developmental disruption can provide a foundation for GMS-based clinical decision making.

The robust inter-observer reliability demonstrated across multiple validation studies establishes GMS as a reproducible clinical instrument.[5,6,14] The original validation showing 93% agreement between independent observers, combined with subsequent photo-based validation studies, confirms that GMS can maintain consistency across different clinical contexts and observer experience levels.[6] However, the moderate variability noted in glans and urethral plate assessments highlights persistent subjective elements that limit perfect reproducibility.[42] This recognition has catalyzed the development of complementary scoring systems (POST, GUMS) that address specific limitations while building upon the GMS foundation.[15,18,19]

Despite its comprehensive scope, this review has certain limitations. First, the included studies were predominantly single-center and geographically concentrated, limiting global generalizability. Second, heterogeneity in how the GMS score was applied, whether as a continuous or categorical variable, or with modified thresholds, impeded direct comparison across studies. Third, subjective interpretation of glans and urethral plate anatomy, especially in photo-based scoring, affected interobserver consistency. Few studies reported disaggregated component scores, and formal observer training was often lacking. Finally, most studies focused on early surgical outcomes, with limited data on long-term functional or psychosocial results key concerns for patients and families.

While the GMS score provides a structured and reproducible preoperative assessment of hypospadias severity, evidence from the included studies indicates that intraoperative reassessment remains essential. Dynamic findings such as urethral plate quality, degree of chordee, and intraoperative meatal mismatch may differ from preoperative evaluation and can necessitate modification of the planned surgical approach, particularly in patients with higher GMS scores. These variations have been shown to influence postoperative outcomes, including complication rates and the need for staged repair.

Addressing the existing gaps through standardized scoring protocols, multi-center prospective validation, and longitudinal outcome studies will be essential for optimizing the clinical utility of GMS-based systems.

CONCLUSIONS

This systematic review and meta-analysis affirms the GMS score as a validated, reliable, and clinically useful tool for assessing hypospadias severity. Its consistent association with surgical outcomes, particularly postoperative complications, supports its role in preoperative planning, risk stratification, and shared decision-making. While GMS enhances anatomical assessment, its integration with AI, image-based tools, and emerging scoring systems reflects its adaptability to precision medicine. Standardization of scoring protocols, improved training, and further research into long-term functional and cosmetic outcomes will be key to optimizing its global utility in hypospadias care.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.