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Endometrium of uterus

The endometrium is the inner mucosal lining of the uterus. It undergoes cyclic changes during the menstrual cycle under the influence of estrogen and progesterone. These changes prepare the uterus for possible implantation of a fertilized ovum. If implantation does not occur, the functional layer is shed during menstruation. The endometrium is also clinically significant as the origin of several gynecological disorders including endometrial hyperplasia, polyps, and carcinoma.

Synonyms

  • Uterine lining

  • Endometrial mucosa

  • Uterine mucous membrane

Location and Layers

  • Basal layer (stratum basale):

    • Deep layer adjacent to the myometrium

    • Provides regenerative cells to restore the functional layer after menstruation

  • Functional layer (stratum functionale):

    • Superficial layer subject to hormonal changes

    • Thickens under estrogen and progesterone influence

    • Shed during menstruation if implantation does not occur

Relations

  • Anteriorly: Urinary bladder (via uterovesical pouch)

  • Posteriorly: Rectum (via rectouterine pouch of Douglas)

  • Laterally: Broad ligaments of the uterus and uterine arteries

  • Inferiorly: Continuous with the endocervical canal

Function

  • Provides a receptive surface for embryo implantation

  • Supports early embryo development via secretions (glycogen, lipids, proteins)

  • Sheds cyclically during menstruation if fertilization does not occur

  • Acts as a barrier and immune-modulating tissue during conception

Clinical Significance

  • Endometrial hyperplasia: excessive thickening, often due to unopposed estrogen

  • Endometrial carcinoma: one of the most common gynecological cancers

  • Endometritis: infection/inflammation of the endometrium

  • Infertility: linked to endometrial receptivity issues

  • Imaging evaluation is critical for assessing endometrial thickness, lesions, and pathology

MRI Appearance

T1-weighted images:

  • Endometrium appears with intermediate-to-high signal intensity depending on phase of cycle

  • Hemorrhagic or pathological changes may appear bright

T2-weighted images:

  • Endometrium appears with high signal intensity, sharply demarcated from low-signal myometrium

  • Thickness and signal vary with cycle (thin in early proliferative, thickened in secretory phase)

STIR (Short Tau Inversion Recovery):

  • Endometrium appears bright and well contrasted from surrounding structures

  • Useful for identifying edema, inflammation, or infiltrating pathology

T1 Fat-Sat Post-Contrast:

  • Normal endometrium enhances strongly and uniformly

  • Malignancy may show heterogeneous or irregular enhancement

  • Polyps may appear as enhancing intracavitary structures

CT Appearance

Non-Contrast CT:

  • Endometrium is not well visualized unless thickened or containing hemorrhage

  • Thickened endometrium may appear as a soft tissue density within the uterine cavity

Post-Contrast CT:

  • Endometrium enhances diffusely in normal states

  • Hyperplasia or malignancy appears as abnormally thickened, irregular, or heterogeneously enhancing endometrium

  • Intracavitary lesions such as polyps may be detected with contrast

MRI image

Endometrium of uterus MRI sagittal image anatomy image-img-00000-00000

CT image

Endometrium of uterus CT sagittal image anatomy image-img-00000-00000