Topics

Topic

design image
Obturator lymph nodes

The obturator lymph nodes are a group of pelvic lymph nodes located within the obturator fossa. They are closely related to the obturator nerve and vessels and are part of the internal iliac lymphatic chain. These nodes are clinically significant in the staging and spread of pelvic malignancies, particularly cervical, prostate, bladder, and rectal cancers.

Synonyms

  • Obturator fossa lymph nodes

  • Pelvic obturator nodes

  • Obturator canal nodes

Location

  • Found within the obturator fossa

  • Situated along the obturator nerve and obturator vessels

  • Positioned between the external iliac and internal iliac lymph node groups, often forming a bridge in lymphatic spread

Relations

  • Anteriorly: Obturator externus muscle

  • Posteriorly: Obturator internus muscle and pelvic wall

  • Superiorly: External iliac vessels

  • Inferiorly: Upper fibers of the adductor muscles

  • Medially: Bladder and pelvic organs

  • Laterally: Pelvic sidewall

Function

  • Receive lymph from the pelvic organs including bladder, cervix, prostate, vagina, and rectum

  • Contribute to lymphatic drainage of the upper medial thigh via deep channels

  • Act as key filter stations for tumor spread in pelvic malignancies

  • Support immune function by trapping pathogens and malignant cells

Clinical Significance

  • Frequently involved in pelvic malignancies (cervical, uterine, bladder, prostate, and rectal cancers)

  • Their involvement is a crucial factor in cancer staging and prognosis

  • Obturator node dissection is part of pelvic lymphadenectomy in oncologic surgery

  • Enlarged nodes may compress the obturator nerve, causing medial thigh pain or sensory changes

  • Can harbor metastatic deposits even when other pelvic nodes appear normal

MRI Appearance

T1-weighted images:

  • Nodes appear as oval structures with low-to-intermediate signal intensity

  • Fatty hilum, if present, appears with high signal intensity

T2-weighted images:

  • Nodes typically show intermediate to high signal intensity

  • Pathological nodes may lose the normal internal architecture

STIR (Short Tau Inversion Recovery):

  • Normal nodes show intermediate signal intensity

  • Enlarged or malignant nodes show bright hyperintensity and often loss of fatty hilum

T1 Fat-Sat Post-Contrast:

  • Normal nodes enhance mildly and uniformly

  • Malignant nodes show heterogeneous or irregular enhancement

  • Necrotic nodes may show peripheral rim enhancement with a central non-enhancing area

CT Appearance

Non-Contrast CT:

  • Appear as soft tissue density nodules along the obturator vessels and nerve

  • Normal fatty hilum, if visible, shows as a central low-density area

  • Enlarged or pathological nodes appear as solid soft tissue masses

Post-Contrast CT:

  • Normal nodes enhance mildly and evenly

  • Malignant nodes show irregular or heterogeneous enhancement

  • Necrotic or infected nodes demonstrate rim enhancement with central low attenuation

CT image

Obturator lymph nodes ct axial anatomy image-img-00000-00000