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Topic

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Foreskin

The foreskin, or prepuce, is a specialized double-layered fold of skin and mucous membrane that covers and protects the glans penis. It is a mobile structure that develops embryologically as a distal extension of penile skin and becomes retractable during childhood or adolescence. The foreskin is rich in nerve endings, blood vessels, and lymphatic supply, contributing to protective, sensory, and immunological functions.

The structure is clinically relevant in urology, dermatology, and radiology due to conditions such as phimosis, paraphimosis, balanitis, and its role in circumcision.

Synonyms

  • Prepuce

  • Penile prepuce

  • Penile foreskin

Structure and Layers

  • External layer: Keratinized skin continuous with penile shaft skin

  • Internal layer: Thin mucosal epithelium lining the inner surface, continuous with mucosa of the glans penis

  • Frenulum: A midline fold on the ventral side connecting foreskin to glans, rich in sensory innervation

  • Preputial sac (space): Potential space between foreskin and glans when non-retracted

Relations

  • Anteriorly: Free margin of foreskin covering glans penis

  • Posteriorly: Continuous with skin of penile shaft

  • Ventrally: Attached to glans penis via frenulum

  • Internally: Lies over and protects urethral meatus and glans

Function

  • Protects the glans penis from mechanical trauma, dryness, and infection

  • Provides mobility for smooth gliding during erection and intercourse

  • Contains specialized nerve endings (Meissner’s corpuscles) contributing to penile sensitivity

  • Secretes smegma (via preputial glands), which aids in lubrication

  • Plays an immunological role with Langerhans cells in the mucosal layer

Clinical Significance

  • Phimosis: Inability to retract foreskin, common in children and some adults

  • Paraphimosis: Trapped retracted foreskin behind glans, a urologic emergency

  • Balanitis/posthitis: Inflammation of glans/foreskin, often due to infection or irritation

  • Circumcision: Surgical removal of foreskin, performed for medical, cultural, or religious reasons

  • Cancer risk: Chronic inflammation or poor hygiene may increase risk of penile carcinoma

  • Imaging relevance: Seen in MRI/CT studies for penile trauma, infection, or tumor staging

MRI Appearance

T1-weighted images:

  • Foreskin shows low-to-intermediate signal intensity

  • Fat in adjacent penile shaft appears bright, outlining the prepuce

T2-weighted images:

  • Foreskin has intermediate signal intensity

  • Edema, infection, or inflammation increases signal intensity

STIR (Short Tau Inversion Recovery):

  • Normal foreskin appears as low-to-intermediate signal

  • Inflammatory changes, edema, or tumor involvement appear bright

T1 Fat-Sat Post-Contrast:

  • Normal foreskin enhances mildly and uniformly

  • Pathological foreskin (infection, tumor, inflammation) shows heterogeneous or rim enhancement

3D T2 SPACE / CISS:

  • Foreskin appears with intermediate signal compared to muscle

  • Bright surrounding structures (CSF-equivalent or fat) help outline its thin layers

  • Useful for assessing fine preputial details and relation to glans

CT Appearance

Non-Contrast CT:

  • Foreskin appears as thin soft tissue density covering glans penis

  • Fat in surrounding penile shaft enhances contrast

  • Edema or mass may appear as soft tissue thickening

Post-Contrast CT:

  • Normal foreskin enhances mildly and evenly

  • Infection or tumor may show irregular or heterogeneous enhancement

  • Abscess formation appears as rim-enhancing lesion with central low attenuation

MRI image

Foreskin of penis mri axial anatomy image-img-00000-00000