Figure 1. Anatomical variables utilized for the determination of the urethral defect–based categorization system. B-B indicates the imaginary line between the 2 glanular knobs; UDR, urethral defect ratio.

Figure 2. Intraoperative image of the ventral aspect of the penile shaft of a hypospadias case that traditionally is categorized as glanular hypospadias based on meatal-based classification schemes. On the contrary, the urethral defect ratio system is based on the location of the spongiosa bifurcation in relation to the penile length. In this particular case, the stretched penile length is 53 mm, and the urethral defect (ie, the distance between the glanular knobs and the spongiosa bifurcation) is 32 mm. Therefore, urethral defect ratio = urethral defect/stretched penile length (32/53) = 0.6, which represents class 2.

The severity of the disease and the available repair options depend on the degree of hypospadias present. As a result, many different categorization systems have been created to evaluate the severity of hypospadias depending on the location of the urethral meatus. Unfortunately, the true location of spongiosal bifurcation is not reliably considered by these classification schemes. Certain forms of distal hypospadias are linked to proximal spongiosal hypoplasia and penile curvature (which may necessitate extensive or staged surgical treatment), whereas other, seemingly severe occurrences of proximal hypospadias can provide less of a surgical challenge where favorable anatomy is already present. Surgeons who specialize in treating hypospadias have known for quite some time that the location of the external meatus does not give any clear indication of the degree of the condition or the difficulty of its surgical correction.^1,2 It was also demonstrated that meatal position is not a reliable predictor of postoperative problems, demonstrating the importance of looking at the full hypospadias complex rather than just the meatus.³ A method for objectively evaluating the severity of hypospadias stays an important challenge in the field.⁴ Some tools to standardize the quantification of urethral plate quality and penile curvature have been introduced.^5-7

Merriman et al proposed the Glans-Urethral Meatus-Shaft (GMS) classification scheme, which takes into account not only the placement of the meatus but also glans characteristics such as size, existence, and aspect of glans groove, and degree of ventral curvature.⁸ Nonetheless, there is still a great deal of subjectivity involved in assessing these clinical characteristics.¹ Despite ongoing efforts to standardize, this variation in evaluation and classification hinders fair comparisons of results between institutions and surgeons. Lately, machine learning algorithms have emulated expert human classification of patients with distal/proximal hypospadias, potentially paving the way for future therapeutic applications and standardization of these technologies.⁹ As with any grading system, the optimum categorization for the intensity of hypospadias should be objective and simple to reproduce.

Abbas introduced the urethral defect-based categorization system, where the urethral defect ratio was computed by dividing the magnitude of urethral defect (distance between glandular knobs and bifurcation of the corpus spongiosum) by stretched penile length.¹⁰ The degree of hypospadias was then classified into 3 distinct classes (urethral defect ratio 0.5, 0.5-0.99, and 1.0; Figure 1).

The urethral defect-based categorization system also sheds new light on other crucial aspects of hypospadias, such as potential etiological/genetic causes and a family history of comparable defects. For instance, grade 1 is commonly associated with the familial occurrences and history of hypospadias in another family member, whereas grade 3 is related to the concept with pathologies related to placental insufficiency and preterm, etc. Similarly, cases of grade 3 carry a high risk of concomitant genital and extragenital abnormalities, which should be searched for and adequately addressed (Figure 2).