Epispadias refers to a rare urogenital birth defect of the urethra found in both males and, more rarely, females assigned at birth in which the urethral tube fails to tubularize as usual. As a result, the urethral opening is found on the dorsal side rather than the tip of the penis in those assigned male at birth and towards or above the clitoris in those assigned female at birth. In epispadias, the space between the expected and the actual urethral opening remains open.
For reference, the penis has a different definition of dorsal and ventral relative to anatomical standards. Typically, on the human body, dorsal (i.e., posterior) refers to the back portion of the body and ventral (i.e., anterior) to the front part. However, when referring to the penis, the dorsal side describes the top of the penis and ventral refers to the bottom side.
Epispadias is part of the bladder exstrophy-epispadias-complex (BEEC), which is a spectrum of genitourinary malformations. Depending on the severity, BEEC may involve the urinary system, musculoskeletal system; pelvis; abdominal wall; genitalia; and sometimes, the spine and anus. Isolated epispadias is the mildest form of the complex found more frequently in individuals assigned male at birth. Nonetheless, epispadias is rarely identified without other malformations of the BEEC.
Instead of having an opening at the tip of the penis or between the clitoris and the vaginal opening, hypospadias refers to an abnormal opening ventrally on the penis or close to/within the vaginal orifice. On the other hand, epispadias refers to an abnormal opening dorsally on the penis or towards/above the clitoris.
Of note: According to their Greek origins, the prefix hypo- means below and epi- means above, whereas the suffix -spadias refers to the opening of the urethra.
Of the two, hypospadias is more common and is associated with other conditions such as chordee, which is when the penis has a hook shape and curves (usually downward); inguinal hernias, which are protrusions of bowel through the inguinal canal; and cryptorchidism, which is the absence of testes from the scrotum. Epispadias is usually associated with bladder exstrophy, where the bladder protrudes through the abdominal wall. In individuals with female genitalia, a bifid clitoris, which is when the clitoris itself is divided into two parts, can often be identified along with epispadias.The precise cause of epispadias is not fully understood but appears to be related to fetal exposure to low levels of androgens and estrogens.
Epispadias is the result of malformations during embryogenesis, starting from the sixth week of gestation when the genital tubercle (i.e., a fetal tissue responsible for the development of the reproductive system) grows in a posterior direction towards the rectal area instead of in the cranial direction. This leaves the urethral tube on the dorsal side of the genital tubercle, which results in epispadias.
Anatomically, in individuals with male genitals, epispadias can occur in three areas: penopubic, where the base of the penis and the abdominal wall come together; penile, which is somewhere along the penis; and glanular, or near the tip of the penis. The least severe is glanular, and the most severe is penopubic.
In individuals with female genitals, development is stimulated by estrogens. The genital tubercle elongates and forms the clitoris in addition to the urethral folds, which create the labia minora and the vestibule. In the 13th week of gestation, the urethra is formed and is situated anterior to the vaginal canal. Epispadias results if the urethra develops too far anteriorly.Anand, S., & Lotfollahzadeh, S. (2021). Epispadias. In StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK563180/
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