Video: Lymphatics of the posterior abdominal wall

Lymph nodes? Anything but lymph nodes. I hate lymph nodes. Why do we hate lymph nodes? It's always the last thing we look at when exploring a region of the body. We explore the bones, the muscles, the blood vessels, the nerves, the organs - right? But we're all guilty of just skimming over the unsung hero that is the lymphatic system because it seems so complicated and variable. But, maybe, we should give just a little more attention to the system that prevents us from turning into giant water balloons of interstitial fluid and also plays a vital role in defending our body from harmful infection. I'm going to show you right now that learning about the lymphatic system is not as complicated as you might think. Let's take a shot now at the lymphatics of the posterior abdominal wall.

In this tutorial, we're going to discuss several groups of lymph nodes present in the posterior abdominal wall. Don't let the number of lymph nodes present frighten you. Fortunately, lymph nodes are named after their location. In the posterior abdominal wall, this location is related to the abdominal aorta and its branches, so if you're ever confused on how to name a particular group of lymph nodes, try to remember the names of the vessels adjacent to them.

Now in this tutorial, we will present the lymph nodes of the posterior abdominal wall starting from the most central structures of the lymphatic system on the region and moving on to more peripheral ones. We will begin our tutorial with the cisterna chyli - a dilated sac which receives all the lymph of the abdomen - and then move further down to its peripheral contributors to the intestinal trunk, the left lumbar trunk and the right lumbar trunk.

After discussing the groups of lymph nodes associated with each of these trunks, we will focus on the contributing lymphatic vessels and nodes of the right lumbar trunk, then the iliac nodes, and finally, the inguinal nodes. This way we will cover the lymphatic drainage of the posterior abdomen, the pelvic region, and the inguinal region. For now, let's focus on the cisterna chyli and its contributors.

The cisterna chyli is a dilated sac which rests between two great abdominal vessels. The one on the left of the cisterna chyli is the abdominal aorta. On the right of the cisterna chyli, we can normally see the inferior vena cava, but the particular section which is normally adjacent to the cisterna chyli is removed in our image. However, you can imagine the inferior vena cava which normally continues upwards parallel to the abdominal aorta.

The cisterna chyli receives lymph from three lymphatic trunks which in turn receive their lymph from smaller vessels and lymph nodes. These are the intestinal lymph trunk, the right lumbar trunk, and the left lumbar trunk. We'll first talk about the intestinal lymph trunk and its corresponding nodes before we move on to the lumber trunks. In this section, we will also talk about the superior mesenteric lymph nodes, the celiac nodes, and the inferior phrenic nodes.

As you can see here, we have highlighted the intestinal trunk in green. If we take a closer look at our image, we can see that this trunk loops around the right gonadal artery, which is also known as the right testicular artery in males or the right ovarian artery in females, and receives lymph from both superiorly and inferiorly located nodes. Firstly, we're going to focus on the nodes located superiorly to the intestinal lymph trunk which drain exclusively to that trunk. Those groups of nodes are the superior mesenteric nodes, the celiac nodes, and the phrenic nodes. The inferior mesenteric nodes also drain into the intestinal lymph trunk but not as exclusively as the other groups do.

The nodes we're currently seeing highlighted in green are known as the superior mesenteric nodes. These nodes receive afferents from the areas of distribution of the superior mesenteric artery namely the jejunum, the ilium, the cecum, the vermiform process, and the ascending and transverse parts of the colon. They pass on the lymph they receive to the intestinal lymph trunk as we saw earlier.

We've switched our highlights to match the group of nodes known as the celiac nodes. As you can see, these nodes are located at the root of the celiac artery. To understand which areas are drained to these nodes, we should also try to remember the branches of the celiac arterial trunk. You might recall these to be the left gastric artery, the splenic artery, and the common hepatic artery. So you can understand that the celiac lymph nodes receive lymph from the stomach, the duodenum, the pancreas, the liver, the spleen as well as from the greater omentum.

We're now highlighting two lymph nodes located at the root of each inferior phrenic artery. We can see the lymph vessels associated with these nodes as they run parallel to their respective arteries. So we can again gain insight on these areas drained to these nodes if we examine the distribution of the inferior phrenic arteries.

From our image, we can see that these arteries are distributed on the inferior surface of the diaphragm bilaterally. We can also see that the left phrenic artery gives off some branches to the abdominal portion of the esophagus. These two arteries also give off adrenal branches which supply the adrenal glands. So we can safely assume that the inferior phrenic nodes receive lymph from the inferior surface of the diaphragm, the abdominal portion of the esophagus, and the adrenal glands.

Let's move on to the left lumbar lymph trunk. In this section, we will look at the inferior mesenteric lymph nodes, the lateral aortic lymph nodes, and the retroaortic lymph nodes. We're now looking at the left lumbar lymph trunk. You might remember this to be one of the three trunks which drain into the cisterna chyli. This trunk can be seen to drain nodes from the left side of the aorta. The node groups mostly associated with the left lumbar lymph trunk are the left lateral aortic lymph nodes, the inferior mesenteric lymph nodes which we also saw drain to the intestinal lymph trunk, and the retroaortic lymph nodes. We can also later see that the nodes associated with the left common iliac artery and branches drain to this trunk, but we'll refer to these much later. So, for now, let's look at the lateral aortic nodes, the inferior mesenteric nodes, and the retroaortic nodes in more detail.

We'll start with the inferior mesenteric nodes. You can see these nodes highlighted in green. This group of nodes is located at the root of the inferior mesenteric artery, and like the nodes at the root of the celiac arterial trunk or the superior mesenteric artery, this group also drains lymph from the regions where the inferior mesenteric artery is distributed.

This group drains lymph from many other node groups, each associated with a specific branch of the inferior mesenteric artery. However, referring to these structures is beyond the scope of this tutorial. So to understand the function of the inferior mesenteric nodes, we will say that they ultimately drain structures related to the hindgut, and more specifically, they drain the lymph from the descending colon, the sigmoid colon, and the upper part of the rectum.

Our green highlight now fills the lateral aortic nodes. These nodes form a chain on the left side of the aorta in front of the origin of the psoas major and on the left crus of the diaphragm. They're paired to an intermediate group, which also form a chain at the right side of the aorta. Despite that last fact, the two groups have a similar function. They both drain lymph from the iliac lymph nodes on their respective sides. Moreover, they drain lymph from nodes on the gonadal arteries.

We're now looking at a retroaortic lymph node. These nodes are located below the cisterna chyli anteriorly to the bodies of the third and fourth lumbar vertebrae. They receive lymph from the lateral and preaortic nodes. Some of them drain into the left lumbar lymph trunk while others drain directly to the cisterna chyli.

Let's move on and take a look at the right lumbar lymphatic trunk. In this section, we'll also talk about retrocaval lymph nodes, intermediate lumbar lymph nodes, and lateral caval lymph nodes. We have now highlighted the right lumbar lymph trunk. As we can see, this trunk is located laterally and right to the abdominal aorta and behind the inferior vena cava. This trunk drains lymph from several node groups. Among these, we will find the retrocaval lymph nodes and the intermediate lumbar lymph nodes.

Let's start discussing these groups. The group highlighted right now is known as the retrocaval lymph nodes. If you look at these nodes closely, you'll notice that they receive lymph from other lymph node groups particularly nodes which drain the right kidney.

Our green highlight now covers the intermediate lumbar lymph nodes. This is a group of lymph nodes which forms a chain in between the abdominal aorta and the inferior vena cava. These nodes drain to the retrocaval or the lateral caval lymph nodes and receive lymph from adjacent structures as well as nodes near the midline.

We're now looking at the lateral caval lymph nodes which are highlighted in green. These nodes serve a similar role to the lateral aortic nodes draining lymph from the nodes on the right gonadal artery as well as from the iliac nodes.

Next, we'll be looking at the lymph nodes of the pelvis starting with the common iliac lymph nodes. We'll also look at all these node groups which drain to the common iliac lymph nodes. These would be the internal iliac lymph nodes, the external iliac lymph nodes, and the sacral lymph nodes. First up, though, let's take a look at the promontorial lymph nodes which are a subdivision of the common iliac lymph nodes.

The medial nodes of the left and right common iliac nodes are collectively known as the promontorial lymph nodes. They're found in the midline anterior to the promontory of the sacrum in the region where the right common iliac artery crosses the left common iliac vein just inferior to the aortic bifurcation. Hence, they are also known as the subaortic nodes. They receive lymph from the tributaries of external and internal iliac lymph nodes, and like all common lumbar nodes, drain to the lumbar lymph nodes. The common iliac lymph nodes receive lymph from node groups associated with branches of the common iliac artery. So we can expect internal iliac nodes and external iliac nodes to drain to this group of nodes.

We have currently highlighted the internal iliac lymph nodes which surrounds the internal iliac artery and its branches. These nodes receive the lymphatics corresponding to the distribution of the branches of the artery. More specifically, they receive lymphatics from all the pelvic viscera, from the deeper parts of the perineum including the membranous and cavernosus portions of the urethra, and from the buttock and to the back of the thigh. The internal iliac lymph nodes also drain the superior half of the rectum.

Now we're highlighting the external iliac lymph nodes. As you can see, these nodes lie along the external iliac vessels. They're usually eight to ten in number and receive lymph from several regions including the inguinal lymph nodes, the deep lymphatics of the abdominal wall below the umbilicus, and of the adductor region of the thigh. They also receive lymph from the external genitalia, the membranous urethra, the prostate, the fundus of the urinary bladder, the cervix uteri, and the upper part of the vagina.

The last group of lymph nodes we'll discuss before we talk about the inguinal lymph nodes is the group of nodes highlighted in the midline of the posterior pelvic area. These are known as the sacral lymph nodes. These nodes receive lymphatics from the rectum and the posterior wall of the pelvis.

We're now leaving the abdominal area to have a quick look at the lymph nodes surrounding the origin of the femoral artery. We'll start with the superficial inguinal lymph nodes then discuss the deep inguinal lymph nodes and a special node known as the intermediate lacunar lymph node. These lymph nodes form a chain immediately below the inguinal ligament and are much closer to the skin, hence, the name superficial. There are approximately ten of them and they receive lymphatic afferents from the following regions - the abdominal wall below the level of the umbilicus, the back below the level of the iliac crest, the vulva or the skin of the penis and the scrotum, the perineum and the anus, and the medial thigh and the buttock.

Let's have a look now at the deep inguinal lymph nodes. These nodes drain the superficial lymph nodes and then drain to the external iliac nodes. They are located deeper under the skin compared to the superficial inguinal lymph nodes and are very close to the medial surface of the femoral vein.

Finally, we will be discussing a very special node which is considered to be the most superior of the deep inguinal nodes and the most inferior of the external iliac nodes. This node is known as the intermediate lacunar lymph node but is also known as Cloquet's node or Rosenmueller's node. This node, similar to the other deep inguinal nodes, receives lymph from more superficial nodes. It is special in that it is located directly under the inguinal ligament.

Alright, let's move on to some clinical notes now. To highlight the importance of the anatomy of lymph nodes and the course of lymph in the nodes we have already discussed, we will examine a condition known as lymphadenopathy.

Lymphadenopathy is a term referring to disease of the reticuloendothelial system resulting in enlargement or change in consistency of lymph nodes. As such, it can affect any lymph node of the body; however, right now, we're looking at superior mesenteric lymph nodes which drain the small bowel, the ascending colon, and the transverse colon. So we'll examine the causes of lymphadenopathy in this region.

Lymphadenopathy can be due to a wide variety of causes, most commonly infection, but since the reticuloendothelial system is involved in dealing with autoimmune disorders and malignancies, lymphadenopathies can occur under such circumstances. One particularly common cause of adult malignancy which can present with mesenteric lymphadenopathy at advanced stages is colon cancer.

Say, for example, that a malignant collection of cells develops on the ascending colon. At some point, the tumor may penetrate the basement membrane of the epithelium. Its cells would then begin to proliferate in underlying connective tissue and then be carried off to the lymphatic system partly by active movements and partly by the hydrostatic pressure. Cancer cells would then begin proliferating in nearby lymph nodes resulting at localized lymphadenopathy. If the cancer is not diagnosed and treated, cancer cells can continue invading nodes along the flow of lymph and spreading to other organs.

Alright, well done! You're at the end of the tutorial now, let's quickly recapped what we've covered today.

So let's sum up what we've learnt on the anatomy of the lymphatics of the posterior abdominal wall. First and foremost, we should point out that most lymph node groups are named based on their corresponding artery and that they usually drain lymph from the regions of distribution of this artery. This being clarified, let's remember that we've talked about the cisterna chyli as the region where all lymph from the posterior abdomen collects. The cisterna chyli receives lymph via three lymph trunks - the intestinal trunk here, the left lumbar trunk here, and the right lumbar trunk here.

The intestinal trunk, if you remember, drains the celiac nodes which receive lymph from the stomach, duodenum, and omental surfaces; the superior mesenteric nodes which receive lymph from the small bowel, the ascending colon, and half the transverse colon; and from the phrenic nodes which drain the diaphragm.

Now regarding the left lumbar trunk, we've already mentioned that it receives lymph from the inferior mesenteric nodes which drain the lymph from the descending and sigmoid colon, the lateral aortic nodes, and the retroaortic nodes. We should also clarify at this point that these node groups drain the common iliac lymph nodes.

Regarding the right lumbar trunk, we should remember that it receives lymph from the retrocaval lymph nodes which drain the kidney and the aortic nodes, the lateral caval lymph nodes, and the intermediate lumbar lymph nodes which in turn mostly receive lymph from the common iliac lymph nodes.

Now continuing to the iliac lymphatic anatomy, we've established that the common iliac lymph nodes receive lymph from both the internal iliac lymph nodes which drain the perineum and the pelvic viscera as well as the external iliac lymph nodes which drain the genitalia, urethra, and deeper pelvic nodes. In addition to that, we also mentioned the promontorial nodes, a subdivision of the common iliac nodes found near the bifurcation of the abdominal aorta. The promontorial lymph nodes drain into the lumbar lymph nodes.

Next, we briefly discussed the anatomy of the inguinal nodes - those being a continuation of the external iliac lymphatic vasculature in the thigh. We've distinguished between a superficial group of nodes which mostly drain lymph from the skin below the umbilicus, the skin of the genitalia, and the buttock; and a deep group of nodes which drain the superficial lymph nodes and further drain to the iliac nodes.

Finally, we briefly talked about lymphadenopathy, its common causes, and how malignant cells from a growing colon cancer can spread to the lymph nodes draining the colon.

And that's it! Thanks for watching and happy studying!