External iliac lymph nodes
The external iliac lymph nodes lie anterior to the internal iliac lymph nodes and usually form three separate subgroups according to their relation to the external iliac artery:
- lateral (considered the main channel of drainage)
The efferent channels pass on towards the common iliac nodes. The nodes collect lymph from the:
- infraumbilical abdominal wall
- adductor region of the thigh
- glans penis/clitoris
- membranous urethra
- fundus of bladder
- uterine cervix and upper vagina
Structural features remain as diagnostic standards for evaluation of pelvic lymph nodes. The size threshold of pelvic nodes ranges from 0.5 to 2 cm. A short axis diameter <1 cm in oval nodes or <0.8 cm in round nodes is considered the upper limit of normal . Using these parameters, the specificity for detecting positive pelvic nodes on CT reaches 97%, but with a low sensitivity of 34% .
The external iliac nodes are an important nodal group when considering lymphatic spread of pelvic malignancy. The lymphatic drainage patterns of urogenital malignancies are complex in the pelvis; however, spread from the pelvic organs to the medial chain of the external iliac nodal group is the most common route through which metastasis can occur .