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Topic

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Uterus

The uterus is a hollow, muscular, pear-shaped organ of the female reproductive system, located in the pelvis between the bladder and rectum. It is responsible for menstruation, implantation of the fertilized ovum, fetal development during pregnancy, and expulsion of the fetus during labor. Its structure, vascular supply, and close relation to pelvic organs make it highly significant in gynecology, obstetrics, surgery, and radiology.

Synonyms

  • Womb

  • Uterine organ

  • Female reproductive uterus

Location and Parts

  • Located in the true pelvis, posterior to the bladder and anterior to the rectum

  • Normal orientation is anteverted and anteflexed

  • Divided into three main regions:

    • Fundus: Dome-shaped part above the openings of the uterine tubes

    • Body (Corpus): Central and largest portion, contains the endometrial cavity

    • Cervix: Cylindrical lower portion projecting into the vagina, contains internal and external os

Relations

  • Anteriorly: Urinary bladder and vesicouterine pouch

  • Posteriorly: Rectum and rectouterine pouch (pouch of Douglas)

  • Laterally: Broad ligaments, uterine vessels, and ureters

  • Superiorly: Intestinal loops may overlie the fundus

  • Inferiorly: Connects with the vagina via the cervical canal

Layers

  • Endometrium: Inner mucosal lining, undergoes cyclical changes during menstruation

  • Myometrium: Thick muscular middle layer, responsible for contractions during labor

  • Perimetrium: Outer serosal covering (peritoneum)

Function

  • Menstrual cycle regulation and shedding of endometrium

  • Site of implantation for the fertilized ovum

  • Provides protection and nourishment for the fetus

  • Contracts to expel the fetus during childbirth

Clinical Significance

  • Common site for fibroids (leiomyomas), adenomyosis, endometrial hyperplasia, and malignancies

  • Central in conditions such as endometriosis, infertility, abnormal uterine bleeding

  • Assessment of uterine size and position is important in pregnancy and pelvic imaging

  • Target of surgical procedures such as hysterectomy, myomectomy, and cesarean section

MRI Appearance

T1-weighted images:

  • Myometrium shows low-to-intermediate signal intensity

  • Endometrium appears slightly higher signal intensity than myometrium

  • Hemorrhage (as in endometriosis) may show high signal foci

T2-weighted images:

  • Endometrium appears bright

  • Junctional zone (inner myometrium) appears low signal intensity

  • Outer myometrium shows intermediate signal intensity

  • Fibroids appear as well-defined low signal masses

STIR (Short Tau Inversion Recovery):

  • Normal uterus: intermediate to low signal

  • Edema, adenomyosis, or fibroids with degeneration appear hyperintense

T1 Fat-Sat Post-Contrast:

  • Myometrium enhances homogeneously

  • Endometrium enhances less intensely

  • Fibroids may enhance heterogeneously

  • Malignant lesions show irregular or intense enhancement

CT Appearance

Non-Contrast CT:

  • Uterus appears as a soft tissue density structure in the pelvis

  • Endometrium is usually indistinct on non-contrast scans

  • Calcified fibroids may be visible

Post-Contrast CT:

  • Uterine myometrium enhances uniformly in the normal uterus

  • Fibroids may enhance heterogeneously or less than the surrounding myometrium

  • Malignancies may appear as irregularly enhancing masses with possible invasion of adjacent structures

MRI image

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MRI image

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CT image

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