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Endocervical canal

The endocervical canal is the tubular passage within the cervix that connects the endometrial cavity of the uterus with the vaginal canal. It is an essential structure for reproductive health, serving as the conduit for menstrual flow, sperm passage, and childbirth. Its mucosa contains glands that secrete protective cervical mucus, which varies with the menstrual cycle. The canal is clinically significant in gynecology, obstetrics, and oncology due to its role in fertility, cervical pathology, and as a site for diagnostic procedures such as Pap smears.

Synonyms

  • Cervical canal

  • Cervical os pathway

  • Endocervical passage

Location and Structure

  • The endocervical canal lies within the cervix uteri, extending from the internal os (opening into the uterine cavity) to the external os (opening into the vagina).

  • It is approximately 2–3 cm long in non-pregnant women but lengthens during pregnancy.

  • The mucosa is lined by simple columnar epithelium containing mucus-secreting glands.

  • The canal’s lumen is fusiform in shape and varies with age, hormonal status, and parity.

Relations

  • Superiorly: Continuous with the uterine cavity at the internal os

  • Inferiorly: Opens into the vaginal cavity at the external os

  • Anteriorly: Related to the bladder and vesicouterine pouch

  • Posteriorly: Related to the rectouterine pouch (pouch of Douglas)

Function

  • Provides a passageway for menstrual blood from the uterus to the vagina

  • Allows entry of sperm into the uterine cavity for fertilization

  • Produces cervical mucus, which changes consistency during the menstrual cycle to regulate fertility and protect against pathogens

  • Acts as a barrier during pregnancy, with the mucus plug protecting the uterine environment

  • Dilates during labor to permit childbirth

Clinical Significance

  • Site for Pap smear sampling to screen for cervical dysplasia and cancer

  • Commonly involved in conditions such as cervicitis, cervical stenosis, polyps, carcinoma

  • Plays a role in infertility evaluation (mucus quality and canal patency)

  • Imaging of the canal is important in detecting tumors, congenital anomalies, or obstructive lesions

  • Instrumental in procedures such as hysterosalpingography, hysteroscopy, and cervical cerclage

MRI Appearance

T1-weighted images:

  • Canal appears as a low-signal lumen

  • Surrounding cervical stroma appears intermediate to low signal

  • Mucus may appear bright if proteinaceous or hemorrhagic

T2-weighted images:

  • Canal appears as a high-signal lumen (fluid/mucus-filled)

  • Cervical stroma shows characteristic low-signal intensity forming a dark ring around the canal

  • Useful for delineating cervical pathology such as carcinoma or polyps

STIR (Short Tau Inversion Recovery):

  • Canal lumen appears bright if fluid/mucus present

  • Cervical stroma remains low signal

  • Pathological lesions show hyperintensity compared to stroma

T1 Fat-Sat Post-Contrast:

  • Normal canal does not enhance

  • Cervical stroma enhances uniformly

  • Neoplasms, polyps, or inflammation show focal or heterogeneous enhancement

CT Appearance

Non-Contrast CT:

  • Canal not well visualized unless distended

  • Appears as a soft tissue density within the cervix

  • Calcifications may be present in chronic inflammation or post-treatment

Post-Contrast CT:

  • Cervical stroma enhances

  • Canal lumen appears as a non-enhancing central tract if fluid-filled

  • Pathology (tumors, infection, obstruction) shows variable enhancement patterns

MRI image

Endocervical canal MRI SAGITTAL anatomy image-img-00000-00000

MRI image

Endocervical canal MRI axial anatomy image-img-00000-00000

CT image

Endocervical canal CT axial anatomy image-img-00000-00000

CT image

Endocervical canal CT SAGITTAL anatomy image-img-00000-00000