Pelvic nodes that are typically harvested lie betweeen the external iliac vessels and the obturator vessels. For some cancers (e.g., uterine and cervical CA) harvesting the nodes can be curative.
Begin with the skeleton and key ligaments. (At any time you can rotate the image or add or subtract structures. Clicking the red hyperlink will bring you back to a starting point. The axial and coronal images are set to illustrate relationships with the heads of the femur that can orient you when viewing an MRI or CT. Use mouse rollovers to identify the heads of the femur, bladder, and uterus. The mid sagittal image emphasizes the relationships of the bladder, uterus, cervix, and vagina. Any coloration in the 3D image will be shown in the cross-sections.)
Add the iliopsoas muscle to one side, as a reference. This is an easy structure for the surgeon to identify.
What does it do?
It is a powerful flexor of the hip.
Now add the external iliac and femoral vessels.
Name the branches of the external iliac and femoral arteries that supply the pelvis.
They have no branches to the pelvis. The external iliac is just passing through the pelvis to the thigh where it becomes the femoral artery.
The external and internal iliac vessels lie in the lateral walls of the pelvis. The lymph nodes to be harvested are found on the pelvic wall between these vessels. Note the anatomic variation: this women has two right internal iliac veins instead of just one.
Why are lymph nodes located here?
The pelvis is supplied by the internal iliac artery and its branches. The branches travel anteriorly along the pelvic wall to reach the bladder and uterus. Lymphatics flow backwards along this arterial tree.
Name the primary branches of the internal iliac artery that supply pelvic viscera.
Inferior vesical, uterine, vaginal and umbilical arteries
One approach to the lymph nodes is to incise the peritoneum along the external iliac vessels to separate them from the iliopsoas muscle, thereby creating an opening into the retroperitoneal plane. Open the plane with your hand, using a sweeping motion. The peritoneum and all the blood vessels will be safely separated from the lateral pelvic wall. All the lymph nodes can be quickly and safely harvested with minimal risk to these vessels and nerves. However, several structures may be dangerously stretched: The genitofemoral nerve (not seen), deep circumflex iliac artery, and ureter will be placed at risk of injury. The ureter (purple) is hard to locate in the cross-sections, but look for it in the center of the images.
What is the function of the genitofemoral nerve?
The genital branch innervates the cremasteric muscle and provides sensory fibers to the skin over the scrotum in men and to the mons pubis and labia majora in women. The femoral branch provides sensation for the skin over the femoral triangle.
Another structure that would be placed at risk is the obturator nerve.
What is the territory of this nerve? What action would be compromised if it were injured?
The adductor compartment of the thigh. Adduction at the hip would be compromised.
A large lymph node is often found by the deep inguinal ring. A guide to this location is the round ligament of the uterus. For the male pelvis, this guide would be the vas deferns. We can identify some of the male pelvic lymph nodes.
When performing this procedure be aware of the following important anatomy: