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Ejaculatory duct

The ejaculatory ducts are paired tubular structures of the male reproductive system that convey sperm and seminal fluid into the urethra. Each duct is formed by the union of the duct of the seminal vesicle and the ampulla of the vas deferens. The ducts pass through the prostate gland and open into the prostatic urethra at the seminal colliculus. They play an essential role in reproduction by providing the pathway for semen during ejaculation.

Synonyms

  • Seminal vesicle-vas deferens duct

  • Male prostatic ejaculatory duct

  • Ductus ejaculatorius

Location and Course

  • Origin: Formed by the union of the duct of the seminal vesicle and the ampulla of the vas deferens

  • Course:

    • Each duct is short (approximately 2 cm in length)

    • Passes anteromedially through the prostate gland

    • Runs obliquely within the prostate to approach the midline

  • Termination: Opens into the prostatic urethra at the seminal colliculus, lateral to the prostatic utricle

Relations

  • Anteriorly: Prostatic urethra

  • Posteriorly: Seminal vesicles and rectovesical fascia

  • Laterally: Prostatic tissue

  • Medially: Prostatic utricle

Function

  • Transmits sperm from the vas deferens and secretions from the seminal vesicles into the urethra

  • Plays a key role in ejaculation and fertility

  • Ensures semen is delivered into the urethra during orgasm

Clinical Significance

  • Obstruction (congenital or acquired): May cause infertility, hematospermia, or painful ejaculation

  • Cysts or dilatation: Ejaculatory duct cysts can mimic midline prostatic cysts

  • Infections: Can be affected by prostatitis or seminal vesiculitis

  • Tumors: Rare but may involve or compress the ducts

  • Evaluated with MRI and CT, especially in infertility workup

MRI Appearance

T1-weighted images:

  • No fluid: Ducts appear as thin, dark tubular structures within the prostate

  • Simple fluid (semen): Appears dark (low signal intensity)

  • Fat: Appears bright, providing contrast against ducts

  • Blood/proteinaceous material: May appear bright

T2-weighted images:

  • No fluid: Ducts may not be clearly visible, only thin hypointense lines in prostate

  • Simple fluid: Appears bright

  • Fat: Intermediate to bright

  • Obstructed/expanded duct with debris or pus: May appear with mixed or bright signal

STIR (Short Tau Inversion Recovery):

  • No fluid: Ducts are not well visualized

  • Fluid: Appears bright hyperintense

  • Fat: Suppressed, appears dark

  • Inflammation/infection: Bright hyperintensity in or around duct

T1 Fat-Sat Post-Contrast:

  • Normal duct: Thin lining with minimal or no enhancement

  • Fluid: Does not enhance

  • Fat: Suppressed, appears dark

  • Pathology (cyst, infection, tumor): Shows focal, heterogeneous, or rim enhancement depending on etiology

CT Appearance

Non-Contrast CT:

  • No fluid: Ducts are not visible, only potential space within prostate

  • Fluid-filled ducts/cyst: Appear as low-attenuation tubular or cystic structures

  • Fat: Low density, separates ducts from surrounding structures

  • Blood or calcifications: Hyperdense areas in ducts

Post-Contrast CT:

  • Normal ducts: Not directly seen, surrounding prostate enhances homogeneously

  • Dilated or cystic ducts: Fluid remains low attenuation, walls may enhance

  • Infection or tumor: Irregular wall thickening, heterogeneous enhancement, or rim enhancement if abscess present

MRI image

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MRI image

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CT image

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