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Labia majora

The labia majora are paired, prominent longitudinal folds of skin forming the outer boundaries of the vulva. They contain adipose tissue, connective tissue, sweat glands, sebaceous glands, and hair follicles, serving both protective and sensory functions. They extend from the mons pubis anteriorly to the perineum posteriorly, enclosing the pudendal cleft and labia minora.

Anatomically, they represent the female homologues of the male scrotum, arising from the labioscrotal swellings in embryological development. They serve as important landmarks in gynecology, obstetrics, surgery, and pelvic imaging.

Synonyms

  • Greater labia

  • External labial folds

  • Outer lips of vulva

Location and Boundaries

  • Anteriorly: Fuse at the mons pubis forming the anterior commissure

  • Posteriorly: Join at the posterior commissure in front of the anus

  • Laterally: Covered externally by skin with hair follicles and sebaceous glands

  • Medially: Enclose the pudendal cleft and labia minora

Relations

  • Anterior: Mons pubis

  • Posterior: Perineum and anal region

  • Lateral: Perineal skin and subcutaneous fat

  • Medial: Labia minora, clitoris, vaginal vestibule

Function

  • Protects the vaginal vestibule, urethral meatus, and clitoris

  • Cushions external genitalia with adipose tissue

  • Contributes to sexual arousal through rich innervation and vascular supply

  • Acts as a barrier against infection and trauma

Clinical Significance

  • Common site for infections, cysts (Bartholin gland cyst if extension occurs), and dermatological conditions

  • Can be affected by trauma, hematomas, or lacerations during childbirth

  • Site of benign and malignant tumors (e.g., vulvar carcinoma, lipomas, cysts)

  • Atrophy and loss of fat tissue occur in menopause and aging

  • Imaging important in cases of suspected abscess, hematoma, or neoplasm

MRI Appearance

T1-weighted images:

  • Fat in labia majora appears bright

  • Skin and fibrous tissue appear dark to intermediate

  • Hematomas may appear iso- to hyperintense depending on age

  • No fluid: labia show fatty bright background with dark skin covering

T2-weighted images:

  • Fat appears bright

  • Skin and fibrous tissue remain low signal

  • Fluid collections or cysts appear bright

  • No fluid: uniform bright fat with thin dark rim of skin

STIR (Short Tau Inversion Recovery):

  • Fat signal is suppressed and appears dark

  • Fluid or edema appears bright

  • No fluid: labia appear uniformly dark with no hyperintensity

T1 Fat-Sat Post-Contrast:

  • Fat is suppressed and dark

  • Normal labial tissue enhances mildly and uniformly

  • Inflammatory or neoplastic lesions enhance heterogeneously

  • Abscess shows rim enhancement with central non-enhancing area

CT Appearance

Non-Contrast CT:

  • Fat in labia majora appears as low attenuation (dark)

  • Skin and fibrous tissue show soft tissue density

  • Hematomas appear as hyperdense regions

  • No fluid: labia show fat density with thin soft tissue rim

Post-Contrast CT:

  • Fat remains dark (no enhancement)

  • Soft tissue components enhance mildly and uniformly

  • Infection or tumor may show irregular or nodular enhancement

  • Abscess appears as low-density center with rim enhancement

MRI image

Labia majora MRI axial anatomy image-img-00000-00000

MRI image

Labia majora MRI coronal anatomy image-img-00000-00000

CT image

Labia majora CT axial image 1

CT image

Labia majora CT axial image 2