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Topic

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External urethral orifice

The external urethral orifice, also called the urethral meatus, is the external opening of the urethra through which urine exits the body. It marks the terminal point of the urinary tract and serves as the passageway for urine excretion. Its position differs in males and females and is an important landmark in clinical examinations, urology, and radiology.

Synonyms

  • Urethral meatus

  • Urethral opening

  • External meatus

Location and Boundaries

  • In females: Located in the vestibule of the vulva, between the clitoris (superiorly) and vaginal opening (inferiorly)

  • In males: Located at the tip of the glans penis, typically at the summit of the penile glans in a vertical slit-like opening

Relations

  • Females: Anterior relation to clitoris, posterior relation to vaginal orifice, lateral relation to labia minora

  • Males: Surrounded by the glans penis, related proximally to the navicular fossa of the urethra

Function

  • Provides the final pathway for urine excretion from the bladder to the outside environment

  • In males, also transmits semen during ejaculation

  • Maintains continence in conjunction with urethral sphincters

Clinical Significance

  • Urethral stenosis/stricture: Narrowing of the meatus can cause difficulty urinating

  • Infection: Common site for entry of pathogens in urinary tract infections

  • Congenital anomalies: Hypospadias (opening on ventral penis) or epispadias (opening on dorsal penis) in males

  • Trauma: Can be injured during catheterization or pelvic trauma

  • Cancer: Rarely, may be site of urethral carcinoma

MRI Appearance

T1-weighted images:

  • Orifice itself not well seen unless pathology present

  • Surrounding fat is bright and provides contrast

  • Scar tissue or mass may appear low signal

T2-weighted images:

  • Urethral lumen at orifice appears bright if fluid-filled

  • Fibrosis or strictures appear low signal intensity

STIR (Short Tau Inversion Recovery):

  • Normal tissues appear dark

  • Inflammation, edema, or infection near the orifice appear bright

T1 Fat-Sat Post-Contrast:

  • Normal orifice shows little to no enhancement

  • Inflammation, tumor, or abscess may show focal or rim enhancement

CT Appearance

Non-Contrast CT:

  • External orifice usually not visible directly

  • Surrounding soft tissues appear normal unless inflamed

  • Pathology (stone at urethral meatus, calcification) may be visible

Post-Contrast CT:

  • Urethral mucosa may enhance slightly

  • Inflammation or tumor appears as enhancing lesion at the orifice

  • Abscess may present as central low density with rim enhancement

MRI image

External urethral orifice MRI sagittal anatomy image-img-00000-00000

MRI image

External urethral orifice MRI axial anatomy image-img-00000-00000

CT image

External urethral orifice CT sagittal anatomy image-img-00000-00000