Lymphatic Vessels and Nodes of the Pelvis
The lymphatic vessels and nodes of the pelvis return lymph drained from pelvic organs, and follow a certain course that generally, but not reliably, follow the pattern of venous drainage of the pelvic structures.
Lymphatic capillaries with fenestrated endothelial cell lining are blind ended tubes found in capillary bed. They merge together forming lymphatic vessels, which possess valves similar to those found in veins.
These lymphatic vessels drain into various series or groups of lymph nodes, which are present in the form of chain or rows. All lymph drained from the pelvic region is returned to the venous circulation via the thoracic duct, which empties its contents in or around the junction of the left internal jugular and subclavian veins.
Since many structures of the pelvis are located along the midline (e.g. prostate, urinary bladder), they are supplied and drained into both sides of pelvis. Pelvic organs are mostly suspended by dense connective tissue suspensory apparatus which carry blood vessels, nerves and lymphatics to these organs. Several groups of lymph nodes have been identified in pelvis and mainly include the sacral, internal, external, and common iliac lymph nodes.
There are several other minor groups of lymph nodes like pararectal nodes in the connective tissue along the branches of internal iliac vessels. The pelvic lymph nodes receive afferent from pelvic, peripheral, visceral and parietal structures and send efferents to proximal group of lymph nodes.
Major lymph Nodes of the pelvis
Iliac lymph nodes
The location and number of several groups and sub-groups of lymph nodes receiving lymph drainage from the pelvic organs vary but four main groups are well known and can be described as follows:
- External iliac nodes: These group of lymph nodes are located above the pelvic brim, along the external iliac vessels. Apart from receiving lymph directly from pelvic structures, especially the superior parts of the middle to anterior pelvic organs, they also receive lymph from the inguinal lymph nodes. These inguinal lymph nodes are the main structures they drain. The external iliac nodes return lymph into the common iliac nodes.
- Internal iliac lymph nodes: These nodes derive their name from the internal iliac vessel. They form a cluster around the anterior and posterior divisions of the internal iliac artery and the origins of the gluteal arteries. They receive drainage from the inferior pelvic viscera, deep perineum, and gluteal region and like the external iliac nodes, drain into the common iliac nodes.
- Sacral lymph nodes: Within the pelvis, at the concavity of the sacrum, lies the sacral group of lymph nodes. They receive lymphatic vessels which course along the median sacral blood vessels. Specifically, they receive lymph from the posteroinferior pelvic viscera and drain either to internal or common iliac group of lymph nodes.
- Common iliac lymph nodes: The common iliac lymph nodes mainly drain other lymph nodes within the pelvis. They are located above the pelvis and receive drainage from the sacral, external iliac and internal iliac groups of lymph nodes. They mainly drain lymph into the caval and aortic groups of lymph nodes. Some direct lymph drainage into the common iliac nodes occurs from some pelvic organs, for example, the direct lymphatic vessels from the neck of the urinary bladder and the inferior parts of the vagina. Depending upon their location this group of lymph nodes is divided into three sub-groups:
- Lateral: direct continuation of external iliac lymph nodes
- Posterior/intermediate: receives lymph from external and internal iliac nodes
- Medial: lies below the aortic bifurcation and receives lymph from internal iliac nodes
Lumbar lymph nodes
All lymph drained from the aforementioned lymph nodes continues superiorly to drain into the lumbar lymph nodes
The right lumbar lymph nodes are composed of the:
- Precaval lymph nodes
- Lateral caval lymph nodes
- Retrocaval lymph nodes
The left lumbar lymph nodes are composed of the:
- Preaortic lymph nodes
- Lateral aortic lymph nodes
- Retroaortic lymph nodes
Interposed between the right and left lumbar lymph nodes are the:
- Intermediate lumbar lymph nodes
Important to note: In females, lymphatic drainage from the ovaries and uterine tubes follow the ovarian veins directly to the lumbar lymph nodes (i.e., the caval and aortic lymph nodes). Similarly, the lymphatic drainage of the testis and epididymis also drain to those lumbar nodes, bypassing the iliac nodes.
The lateral lumbar nodes tend to receive lymph drained from common iliac and sacral nodes, and also from ovaries or testes as mentioned above. The preaortic nodes receive lymph from rectum, anal canal, colon and anterior abdominal wall while retroaortic/retrocaval nodes receive drainage from posterior abdominal wall.
Such sub-groups of lymph nodes, as well as the main groups like those of the pelvis described above, are usually highly interconnected to allow free flow of drainage. However, in some clinical conditions like cancer affecting one organ, there can be a spread to other regions through the interconnecting lymphatic network.
The pelvic lymph nodes are highly interconnected, so that lymphatic drainage (and metastatic cancer) can pass in almost any direction, to any pelvic or abdominal organ.
The lymphatic system of the pelvis is used in the diagnosis and treatment of cancers that affect organs in the pelvic region. Cancer spreads easily from one organ to the other through the lymphatic vessels. Lymph nodes also destroy cancer cells but can also become cancerous itself.
Cancer of the bladder can spread through the internal iliac and obturator nodes. Cervical cancer spreads easily through the internal, external and obturator nodes. Removal of these nodes helps to stop the spread and therefore improves treatment.