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Internal iliac lymph nodes

The internal iliac lymph nodes, also called hypogastric lymph nodes, form an important group of pelvic lymph nodes. They are closely related to the internal iliac vessels and their branches. These nodes receive lymphatic drainage from the pelvic viscera, gluteal region, perineum, and medial thigh, making them critical for pelvic oncology staging and surgical planning.

Synonyms

  • Hypogastric lymph nodes

  • Lateral pelvic lymph nodes

  • Internal pelvic nodes

Location and Groups

  • Distributed along the internal iliac artery and vein and their branches

  • Typically grouped as:

    • Anterior internal iliac nodes: along anterior branches of the internal iliac artery

    • Lateral internal iliac nodes: along the lateral pelvic wall

    • Posterior internal iliac nodes: along posterior branches, near sacral connections

  • Communicate with external iliac, sacral, obturator, and common iliac nodes

Relations

  • Anteriorly: Pelvic viscera (bladder, uterus, rectum)

  • Posteriorly: Sacrum and sacral plexus

  • Laterally: Pelvic sidewall, internal iliac vessels

  • Medially: Pelvic organs and peritoneal reflections

Function

  • Drain lymph from:

    • Pelvic organs (bladder, prostate, cervix, upper vagina, rectum, anal canal above pectinate line)

    • Perineum and medial thigh (via obturator lymphatics)

    • Gluteal region (via gluteal vessels)

  • Act as immunologic filters, trapping pathogens, tumor cells, and debris

  • Serve as major staging nodes in gynecological, urological, and colorectal cancers

Clinical Significance

  • Oncology: Frequently involved in spread of cervical, prostate, rectal, bladder, and uterine cancers

  • Surgery: Target in pelvic lymphadenectomy for cancer staging

  • Infection: May enlarge in pelvic inflammatory disease or tuberculosis

  • Imaging: Crucial landmarks in cross-sectional imaging for pelvic disease staging

MRI Appearance

T1-weighted images:

  • Nodes appear as oval/round low-to-intermediate signal structures

  • Fatty hilum, if preserved, shows bright signal

  • Without fluid: nodes remain solid with clear margins

  • Surrounding fat: bright signal, highlighting nodes

T2-weighted images:

  • Nodes show intermediate-to-high signal

  • Reactive or inflamed nodes may appear brighter

  • Malignant nodes often lose hilum and show more uniform intermediate signal

STIR (Short Tau Inversion Recovery):

  • Normal nodes: Intermediate-to-high signal

  • Pathological nodes: bright hyperintensity, with fatty hilum not visible

  • Surrounding fat: suppressed and appears dark

T1 Fat-Sat Post-Contrast:

  • Normal nodes: mild homogeneous enhancement

  • Reactive nodes: stronger uniform enhancement

  • Malignant or necrotic nodes: heterogeneous enhancement, rim-enhancing necrosis possible

CT Appearance

Non-Contrast CT:

  • Nodes appear as soft tissue density structures along internal iliac vessels

  • Fatty hilum: appears as central low attenuation if preserved

  • Malignant nodes: rounded, enlarged, loss of hilum

Post-Contrast CT:

  • Normal nodes: mild homogeneous enhancement

  • Reactive nodes: stronger, uniform enhancement

  • Malignant or necrotic nodes: heterogeneous or rim enhancement, central low attenuation in necrosis

  • Fat stranding may suggest infection or inflammatory lymphadenitis

MRI image

Internal iliac lymph nodes CT axial anatomy image-img-00000-00000_00001

MRI image

Internal iliac lymph nodes mri coronal anatomy image-img-00000-00000

CT image

Internal iliac lymph nodes CT axial anatomy image-img-00000-00000