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Corpus spongiosum

The corpus spongiosum is one of the three erectile bodies of the penis. It is a cylindrical mass of vascular erectile tissue that surrounds the penile (spongy) urethra. Unlike the paired corpora cavernosa, it remains relatively soft during erection to maintain urethral patency for ejaculation. Proximally, it expands to form the bulb of the penis, and distally, it enlarges to form the glans penis. It is enclosed by a thinner tunica albuginea compared to the corpora cavernosa, allowing greater distensibility.

The corpus spongiosum plays a vital role in urinary and reproductive physiology and is a critical structure in urologic imaging and surgical procedures.

Synonyms

  • Spongy body of penis

  • Corpus cavernosum urethrae (historical)

  • Urethral erectile body

Origin, Course, and Structure

  • Origin: Posteriorly at the perineum as the bulb of the penis, attached to the urogenital diaphragm

  • Course: Extends anteriorly along the ventral aspect of the penis, surrounding the penile urethra

  • Structure:

    • Encloses the urethra in its entire length

    • Surrounded by a thin tunica albuginea and fibrous connective tissue

    • Composed of vascular sinusoids lined by endothelium, separated by trabeculae of smooth muscle and connective tissue

  • Termination: Expands distally to form the glans penis, covering the tips of the corpora cavernosa

Relations

  • Anteriorly: Continuous with the glans penis

  • Posteriorly: Expands to form the bulb of the penis

  • Superiorly (dorsal): Related to the paired corpora cavernosa

  • Inferiorly (ventral): Related to the penile urethra and surrounding fascial layers

  • Laterally: Bounded by Buck’s fascia and penile skin

Function

  • Maintains patency of the urethra during erection by remaining softer than corpora cavernosa

  • Facilitates passage of urine and semen through the penile urethra

  • Contributes to glans engorgement, providing sensory feedback during sexual activity

  • Plays a role in ejaculation and orgasm

Clinical Significance

  • Urethral stricture disease: May cause fibrosis within corpus spongiosum (spongiofibrosis)

  • Penile trauma: Rupture of corpus spongiosum may accompany urethral injury

  • Infection/inflammation: Abscess or periurethral infection may involve corpus spongiosum

  • Tumors: Rare but possible, usually squamous cell carcinoma extending from urethra

  • Surgical relevance: Key structure in urethroplasty, hypospadias repair, and penile prosthesis surgery

MRI Appearance

T1-weighted images:

  • Corpus spongiosum shows intermediate signal intensity

  • Fat in surrounding fascial planes appears bright

  • Hemorrhage (subacute) may appear bright

T2-weighted images:

  • Corpus spongiosum demonstrates intermediate to high signal intensity due to vascular sinusoidal content

  • Fibrosis or scarring appears low signal

  • Surrounding fat appears bright

STIR (Short Tau Inversion Recovery):

  • Normal spongiosum shows  intermediate to high signal intensity

  • Edema, inflammation, or acute trauma appears bright hyperintense

  • Fat is suppressed and appears dark

T1 Fat-Sat Post-Contrast:

  • Normal tissue shows homogeneous mild enhancement

  • Inflammation, tumor, or abscess shows heterogeneous or rim enhancement

  • Fat suppressed: perinodal fat and fascial fat appear dark, aiding visualization

3D T2 SPACE / CISS:

  • Corpus spongiosum appears with intermediate to mildly hyperintense signal compared to muscle

  • Urethral lumen (if fluid-filled) appears bright

  • Provides excellent contrast for evaluating urethral course and periurethral pathology

CT Appearance

Non-Contrast CT:

  • Appears as soft tissue density along ventral penis containing urethra

  • Calcifications (rare) or traumatic hematoma may appear hyperdense

  • Fat around the penis appears as low attenuation, delineating borders

Post-Contrast CT:

  • Corpus spongiosum enhances homogeneously and moderately

  • Urethral or periurethral pathology may enhance irregularly

  • Abscess shows rim enhancement with central low attenuation

MRI image

Corpus cavernosum mri coronal image 1

MRI image

Corpus cavernosum mri coronal image

MRI image

Corpus spongiosum mri axial anatomy image-img-00000-00000