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Seminal vesicle

The seminal vesicles are paired tubular glands of the male reproductive system located in the pelvis. Each vesicle lies posteroinferior to the urinary bladder and superior to the prostate, contributing significantly to seminal fluid production. Their close anatomical relations to the bladder, prostate, rectum, and vas deferens make them highly relevant in urology, radiology, and oncology.

Seminal vesicles are elongated, sacculated structures that typically measure 5–10 cm in length. They are coiled pouches with a lobulated surface, each joining the ductus deferens to form the ejaculatory duct, which then empties into the prostatic urethra.

Synonyms

  • Vesicula seminalis

  • Seminal gland

  • Glandula vesiculosa

Location and Boundaries

  • Superiorly: Base of the urinary bladder

  • Inferiorly: Prostate gland (ejaculatory ducts open into prostatic urethra)

  • Anteriorly: Posterior wall of urinary bladder

  • Posteriorly: Rectum, separated by rectovesical fascia

  • Medially: Vas deferens (ductus deferens) joins vesicle duct to form ejaculatory duct

  • Laterally: Pelvic sidewall and vessels

Relations

  • Anterior relation: Bladder base

  • Posterior relation: Rectum (palpable in digital rectal exam)

  • Inferior relation: Prostate gland

  • Superior relation: Peritoneal reflection of rectovesical pouch

  • Medial relation: Ampulla of ductus deferens

Function

  • Produce ~60–70% of ejaculate volume

  • Secrete alkaline, fructose-rich fluid that nourishes sperm and enhances motility

  • Provide prostaglandins and proteins that aid sperm viability and fertilization

  • Contribute to coagulation and subsequent liquefaction of semen

Clinical Significance

  • Inflammation (vesiculitis): May cause pelvic pain, hematospermia, or infertility

  • Cysts: Can be congenital or acquired, sometimes associated with ejaculatory duct obstruction

  • Neoplasms: Rare but include adenocarcinoma or secondary involvement from prostate or bladder cancer

  • Infections: Commonly occur with prostatitis or epididymitis

  • Imaging relevance: Enlargement, calcification, or altered signal intensity may indicate infection, obstruction, or tumor

MRI Appearance

T1-weighted images:

  • Normal (no fluid): Vesicle walls appear low signal; collapsed lumina may appear dark

  • With normal seminal fluid: Fluid within vesicles is of intermediate-to-high signal intensity (due to protein/seminal content)

  • Hemorrhage/proteinaceous fluid: Appears bright

  • Fat: Surrounding pelvic fat appears bright, outlining vesicles

T2-weighted images:

  • Normal (no fluid): Vesicle appears collapsed, showing low signal

  • With fluid: Fluid appears bright hyperintense, with thin hypointense wall

  • Fat: Intermediate-to-bright signal, outlining structures

  • Chronic changes (fibrosis, tumor): Hypointense thickening of walls

STIR (Short Tau Inversion Recovery):

  • Normal: Vesicle walls low signal, minimal visualization when collapsed

  • With fluid: Fluid appears very bright

  • Fat: Suppressed, appears dark, helping highlight vesicles

  • Inflammation/tumor: Bright hyperintense signal in affected regions

T1 Fat-Sat Post-Contrast:

  • Normal: Mild enhancement of thin vesicle wall; luminal fluid does not enhance

  • Inflammation/tumor: Wall or nodular enhancement, possible irregular thickening

  • Abscess: Peripheral rim enhancement with central non-enhancing core

CT Appearance

Non-Contrast CT:

  • Appear as paired, soft tissue density lobulated structures posterior to bladder

  • With fluid, lumen appears low attenuation

  • Fat around vesicles clearly defines margins

  • Calcifications may be seen in chronic infection or neoplasm

Post-Contrast CT:

  • Vesicle wall enhances mildly and uniformly in normal state

  • Inflammation, infection, or neoplasms produce irregular, nodular, or asymmetric enhancement

  • Abscess appears as central low attenuation with peripheral rim enhancement

MRI image

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MRI image

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CT image

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CT image

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