External Iliac Nodes

The external iliac lymph nodes are a chain of lymph nodes located along the external iliac vessels. They serve as major conduits for lymph drainage from the lower abdominal wall, pelvic organs, and lower limbs. These nodes are essential for the immune surveillance of pelvic and lower limb regions and are commonly involved in the spread of malignancies such as cervical, bladder, and prostate cancers.

Structure

The external iliac lymph nodes are oval or bean-shaped structures organized into three main groups based on their anatomical position relative to the external iliac artery:

• Lateral group: Located lateral to the external iliac artery
• Medial group: Located medial or anterior to the external iliac artery, often adjacent to the vein
• Intercalated (middle) group: Between the artery and vein, more dispersed

Each node consists of a capsule, subcapsular sinus, cortex with lymphoid follicles (B cells), and a medulla with cords and sinuses. Afferent lymphatic vessels enter the node, and filtered lymph exits via efferent vessels to common iliac nodes.

Location

External iliac nodes lie along the length of the external iliac artery and vein, from the level of the inguinal ligament up to the bifurcation of the common iliac artery. They are embedded in the connective tissue of the pelvic sidewall, anterior to the psoas major muscle.

Function

• Lymph drainage: Receives lymph from:
  • Inguinal lymph nodes (especially deep inguinal)
  • Lower abdominal wall
  • Pelvic viscera: bladder, prostate, cervix, upper vagina, lower uterus
• Immune surveillance: Filters lymph for pathogens and tumor cells
• Pathway to common iliac nodes: Efferent vessels drain into common iliac lymph nodes

Clinical Significance

• Oncologic staging: Commonly assessed in cancers of the cervix, bladder, prostate, and testis
• Lymphadenopathy: Enlargement may indicate metastatic spread or infection
• Pelvic lymphadenectomy: These nodes are routinely removed or biopsied in gynecologic and urologic cancers