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Bulbourethral gland (Cowper’s glands)

The bulbourethral glands, also known as Cowper’s glands, are paired pea-sized exocrine glands of the male reproductive system. They are located within the deep perineal pouch and secrete pre-ejaculate fluid that lubricates and neutralizes the urethra prior to ejaculation. The glands are clinically significant due to their involvement in infections, cysts, benign enlargement, and rare tumors.

Synonyms

  • Cowper’s glands

  • Male bulbourethral glands

  • Accessory urethral glands

Location and Structure

  • Situated in the deep perineal pouch, posterolateral to the membranous urethra

  • Each gland is approximately 3–4 mm in diameter in adults

  • Enclosed within fibers of the external urethral sphincter muscle

  • Ducts of the bulbourethral glands pass forward through the perineal membrane to open into the proximal portion of the spongy (penile) urethra

Relations

  • Anteriorly: Membranous and proximal spongy urethra

  • Posteriorly: Perineal body

  • Superiorly: Prostate gland (at base of bladder)

  • Inferiorly: Bulb of the penis

  • Laterally: Fibers of the external urethral sphincter

Function

  • Secretes pre-ejaculate fluid, a clear mucus-like secretion

  • Neutralizes traces of acidic urine in urethra before ejaculation

  • Provides lubrication for sperm passage during ejaculation

  • Contributes to overall seminal fluid composition

Clinical Significance

  • Infection (Cowperitis): Inflammation may cause painful urination and swelling

  • Cysts and syringoceles: Duct obstruction may form cystic dilatation, sometimes visible on imaging or cystoscopy

  • Benign hyperplasia: Enlargement can mimic other pelvic masses

  • Neoplasms: Rare, but bulbourethral adenocarcinoma has been described

  • Surgical relevance: Important landmark in urological procedures and urethral reconstruction

MRI Appearance

T1-weighted images:

  • Gland appears as low-to-intermediate signal intensity relative to surrounding fat

  • Fat planes around gland are bright and help delineate it

  • Cystic changes may appear with low-to-intermediate central signal and high signal if proteinaceous

T2-weighted images:

  • Normal gland shows mildly hyperintense signal

  • Cysts or fluid collections appear bright

  • Solid lesions or fibrosis remain low signal

STIR (Short Tau Inversion Recovery):

  • Gland itself: intermediate signal

  • Fluid or cystic changes: bright hyperintensity

  • Surrounding fat: suppressed and appears dark

T1 Fat-Sat Post-Contrast:

  • Normal gland: mild uniform enhancement

  • Inflammation: diffuse enhancement

  • Cysts: peripheral rim enhancement with non-enhancing center

  • Tumors: heterogeneous enhancement

3D T2 SPACE / CISS:

  • Gland appears as  mildly hyperintense relative to muscle

  • Surrounded by very bright signal from adjacent fat, highlighting ducts clearly

  • Excellent for visualizing ductal dilatation or small cysts

CT Appearance

Non-Contrast CT:

  • Gland is difficult to visualize unless enlarged

  • Appears as a small soft tissue density near membranous urethra

  • Cyst: hypodense lesion in expected location

Post-Contrast CT:

  • Normal gland enhances faintly and may not be well differentiated

  • Inflammatory changes: gland appears enlarged with homogeneous or heterogeneous enhancement

  • Cystic lesions: well-defined hypodense structure with possible rim enhancement

  • Tumors: enhancing mass replacing gland, possibly infiltrative

MRI image

Bulbourethral gland mri axial anatomy image-img-00000-00000