Lymphatics of the Retroperitoneal Space
The abdominal cavity contains the largest portion of our digestive tract in addition to the internal component of our renal system. The lymphatic system responsible for draining these organs, as well as the abdominal musculature, of lymph is found not only adjacent to the individual organs, but also in the retroperitoneal space.
The retroperitoneal, or lumbar lymph nodes and vessels are responsible for draining the lymph from the abdominopelvic gastrointestinal system as well as the deep tissue of the retroperitoneal space. More specifically, they receives lymphatic vessels which drain the skin, muscles, organs and deep tissues of the posterior abdominal wall.
This article will focus on the anatomical locations of these lymph nodes and vessels. Additionally, it will also look at clinically significant points relative to this segment of the lymphatic pathway.
Introduction: Lumbar Lymph Nodes
The retroperitoneal space is defined as the area of the abdominal cavity that is posterior to the parietal peritoneum and anterior to the anterior fascia of the posterior abdominal wall (fascia of quadratus lumborum). The lymph nodes of this cavity are collectively known as the lumbar lymph nodes, and are closely associated with the abdominal aorta and the inferior vena cava.
The lumbar nodes can therefore subdivided into three primary groups:
- the left lumbar lymph nodes, also known as the paraaortic lymph nodes,
- the right lumbar lymph nodes, alternatively known as the paracaval lymph nodes, and,
- the intermediate lumbar lymph nodes, interposed between the abdominal aorta and inferior vena cava.
Paraaortic lymph nodesThe paraaortic lymph nodes are composed of three primary group of nodes:
- The preaortic lymph nodes, located anterior to the abdominal aorta,
- the lateral aortic nodes, located to the left of the abdominal aorta, and,
- the retroaortic nodes, located posterior to the abdominal aorta, against the posterior abdominal wall.
Pre-aortic Lymph Nodes
- celiac lymph nodes,
- superior mesenteric lymph nodes and,
- inferior mesenteric lymph nodes,
The pre-aortic nodes receive lymph from both primary and accessory gastrointestinal organs ranging from the abdominal oesophagus to the anus. The nodes then drain to the intestinal trunk (see below) before draining to the cisterna chyli.
Coeliac Lymph Nodes
The celiac trunk, or celiac axis, is the first and largest branch from the anterior surface of the abdominal aorta. The artery subsequently trifurcates into the left gastric, common hepatic and pancreaticosplenic arteries. Surrounding this large artery and its branches are the coeliac nodes. They are the terminal nodes of the pre-aortic and regional lymph nodes (those associated with the branches of the artery).
- The gastric nodes (surrounding the left gastric artery) drain lymph from the abdominal oesophagus, stomach, proximal duodenum and greater omentum.
- Hepatic nodes are those surrounding the hepatic arteries and biliary tree. They receive lymph from the liver, gallbladder and biliary tree.
- The pancreaticoduodenal nodes are associated with the pancreaticodunal arteries, and as their name suggest, drain portions of the duodenum and head of the pancreas.
- Finally, the pancreaticosplenic group of nodes drain the pancreas, spleen and a portion of the stomach.
Mesenteric Lymph Nodes
The mesenteric nodes are the most caudal of the pre-aortic lymph nodes. They are further subdivided into the superior and inferior mesenteric nodes.
The superior mesenteric nodes are responsible for lymph drainage of the midgut (i.e. from the duodenojejunal flexure to the watershed area of the transverse colon).
The afferents to the superior mesenteric nodes arise from the juxatintestinal nodes (found between the layers of the mesentery), ileocolic nodes (found along the ileocolic artery and its branches) and the mesocolic nodes (within the mesocolon along the transverse colon). The distribution of these nodes and their associated arteries are almost identical.
Likewise, the inferior mesenteric nodes receive lymph from the same areas supplied by the artery for which it was named (i.e. the distal third of the transverse colon, descending colon, sigmoid colon and proximal rectum). This cluster of nodes include smaller groups associated with the sigmoid and left colic arteries, another cluster surrounding the superior hemorrhoidal artery and sigmoid mesocolon and a final pararectal cluster that is found next to the rectum.
The inferior mesenteric nodes will drain to the more superior preaortic lymph nodes, or the lateral aortic lymph nodes (see below).
Lateral Aortic Nodes
As mentioned above, the lateral aortic lymph nodes are located to the left of the abdominal aorta, anterior to the left diaphragmatic crura, sympathetic trunk and medial border of the left psoas major muscle.
Tributaries to these nodes include structures that are perfused by the dorsal and lateral branches of the abdominal aorta. These include the left kidney and left adrenal (suprarenal) glands, ureters, as well as the left testis (in males), or left ovary, uterine tube and cranial portion of the uterus (in females). The deep tissues of the left posterior abdominal wall also drain to this group. The lateral aortic nodes also receive lymph from the common iliac nodes, which receive lymph drained from the pelvis and lower extremities.
Retro-aortic Lymph Nodes
The retro-aortic lymph nodes is the smallest group of para-aortic nodes. While there isn’t a defined set of areas that drain to this set of nodes, it occasionally receives tributaries from the paraspinal posterior abdominal wall. Otherwise, it functions as intermediary group that drains to the lateral aortic nodes, and may also receive lymph drained from the common iliac lymph nodes.
Intermediate lumbar lymph nodes
These nodes may extend over to the area between the inferior vena cava and abdominal aorta. These nodes receive lymph drained from the same organs and tissues as the paraaortic and paracaval lymph nodes, and likewise receive efferent lymphatic vessels of the common iliac nodes.
Paracaval lymph nodes
The paracaval lymph nodes, also known as the right lumbar nodes surround the abdominal portion of the inferior vena cava, located towards to right half of the posterior abdomen.
Similar to the paraaortic nodes, the paracaval nodes can be subdivided into three primary groups: the precaval, lateral caval, and retrocaval lymph nodes.
These nodes have an equivilant function as the paraaortic nodes, in that they drain the same organs, but on the right side of the body i.e. the right kidney, right adrenal (suprarenal) glands, ureter, as well as the right testis (in males), or right ovary,uterine tube and cranial portion of the uterus (in females).
Intestinal Lymph Trunks
The coeliac group of nodes give rise to the intestinal lymph trunk. In addition to receiving afferents directly from the coeliac nodes, it also receives lymph indirectly from the superior and inferior mesenteric nodes and their tributaries. This trunk forms part of the lymph channels in the retroperitoneum that is responsible for draining the abdominopelvic components of the gastrointestinal system.
Lumbar Lymph Trunks
Efferent vessels of the lateral aortic and lateral caval nodes will coalesce and form the left and right lumbar lymph trunks, respectively. In addition to draining the tributaries of the lateral aortic nodes (named above) the lumbar trunks will also carry lymph from the perineal wall, pelvic wall and the region of the anterior abdominal walls caudal to the umbilicus as well as most of the deep tissue of the anterior abdominal wall cranial to the umbilicus.
The left and right branches of the lumbar lymph trunks converge anterolateral to the L1-L2 vertebrae to form the cisterna chyli. This is an approximately 5 – 7 cm long sac-like, fusiform dilatation that receives lymph from the major abdominal trunks.
The cisterna chyli or confluence of lymph trunks extends cranially to the right of the abdominal aorta to form the abdominal part of the thoracic duct at the level of T12 or the thoracolumbar intervertebral disc.
The right lumbar azygous vein and two cranial lumbar arteries are medially related to the cisterna chyli, while the medial border of the right diaphragmatic crus is anteriorly related to the structure. While most of the lymph that passes through the cisterna chyli is delivered by the lumbar and intestinal trunks, it may also receive direct tributaries from the paracaval nodes.
The abdominal lymph trunks along with the cisterna chyli are large vessels that carry a large volume of lymph. This makes it particularly difficult for them to automatically seal following trauma.
Consequently, surgical procedures may be complicated by this factor owing to the close relationship between the lymphatic trunks and the abdominal aorta. Iatrogenic injury of this nature may give rise to a chylous ascites (i.e. ascites secondary to lymph extravasation). It should be noted, however, that this is a rare condition that has several aetiologies.
The lumbar lymph nodes receive lymph from the lower limbs, genitals, pelvic viscera and retroperitoneal structures (including, but not limited to, the suprarenal glands, ureters, ascending and descending colon, kidneys and oesophagus). Tumor metastasis to these nodes from the afore-mentioned sites is not uncommon.
In some cases of testicular carcinoma, renal cell carcinoma and upper urinary tract urothelial carcinoma and other urologic malignancies, a procedure known as retroperitoneal lymph node dissection can be conducted as both a diagnostic and therapeutic procedure.