Video: Lymphatics of the urinary organs

The urinary system – the anatomical machinery that provides the means to keep everything in balance in our body by removing waste like urea, salts, excess water, and other things the body does not need from our blood. The uncontested flusher of the human body, if you will.

That being said, as urinary organs do their work of removing toxins from the blood, they too produce their own toxins, waste, and other junk which they need to dispose of. But how does it get rid of all this metabolic garbage? Let's find out more now as we explore the lymphatics of the urinary organs.

To start with in this tutorial, we'll have a quick look at the main urinary organs to remind ourselves of what they are, their location, and their relationship to each other. Then we'll talk about and discover the various groups of lymph nodes that drain the urinary organs. This will include two main groups of nodes – the lumbar nodes and the pelvic nodes. Finally, we'll be able to put it all together by looking at the drainage by organ. By doing this, we'll see the pathways that lymph takes from the urinary organs to the venous system.

The urinary system is an important system of the body comprised of urinary organs which include the kidneys, ureters, the urinary bladder, and the urethra. This system functions to filter chemical waste products out of the blood which, if allowed to accumulate, obviously becomes toxic to your body. It also helps to remove excess water and maintains blood pressure.

Once all this waste is filtered from our blood by our kidneys, the rest of the organs of the urinary system work to transport, store, and intermittently eliminate the waste products from the blood in the form of urine. This is, of course, known as urination or micturition in the anatomy world. Yes, you heard right. Anatomists micturate. Apparently, the term urinate doesn't quite do it for anatomists, but it means exactly the same thing. So let's begin our exploration of the lymph nodes related to ureters, urinary bladder, and urethra with these ones here which are appropriately known as the pelvic lymph nodes.

This is an umbrella term for all of the lymph nodes located within the pelvis which can be broken down into two major subcategories – the parietal pelvic lymph nodes which lie adjacent to the large blood vessels of the pelvis and the visceral pelvic lymph nodes which lie adjacent to the organs of the pelvis.

The superior most of the parietal pelvic lymph nodes are the common iliac nodes which, as the name suggests, are found around the common iliac artery and vein. They are also sometimes referred to as the superior iliac lymph nodes by clinicians, or even, the posterior iliac lymph nodes by radiologists. Go figure!

The common iliac lymph nodes are at the top of the pelvic lymph node tree, and therefore, have afferent lymphatics from across the pelvic region and limb. This includes all organs of the pelvis except for the testes in males or ovaries in females. Efferent vessels from the common iliac lymph nodes drain to the lumbar lymph nodes which we will discuss later on in the tutorial.

The common iliac lymph nodes can be further subdivided into three groups – the lateral, intermediate, and medial common iliac nodes, which we won't discuss in detail today except for the medial common iliac lymph nodes which are also sometimes referred to as the promontorial lymph nodes, as they overlie the promontory of the sacrum, or alternatively, the subaortic nodes due to their position inferior to the aortic bifurcation.

Next up are the external iliac lymph nodes which are inferiorly continuous with their parents – the common iliac nodes. As you might expect, they are closely related to the external iliac artery and vein, and once again, you'll see them alternatively referred by different names such as the inferior or anterior iliac lymph nodes.

Afferent lymph vessels which are vessels going towards the lymph nodes carry lymph from a wide range of structures such as the inguinal lymph nodes which drain the lower limb, the infraumbilical part of the abdominal wall, the pelvic part of the ureter, parts of the bladder and urethra, as well as the genitalia. As you would expect, the external iliac lymph nodes drain into the common iliac lymph nodes. And just like the common iliac nodes, they can be similarly divided into lateral, intermediate, and medial subdivisions.

We also have the internal iliac lymph nodes which primarily surrounds the internal iliac artery, shown here in the anterior view of the abdomen. They are also sometimes referred to as the hypogastric lymph nodes which makes sense given that the internal iliac artery used to be called the hypogastric artery. They receive afferent lymphatics from many of the pelvic viscera and deeper part of the perineum in addition to the superior half of the rectum and gluteal region of the lower limb.

Like the external iliac lymph nodes, the internal iliac lymph nodes also drain into the common iliac lymph nodes primarily into their medial chain. The internal iliac nodes can also be further divided into three groups – the superior gluteal, inferior gluteal, and lateral sacral lymph nodes. So the iliac lymph nodes which we have just covered all fall under what we called the parietal pelvic lymph nodes.

Let's now take a quick look at some of the nodes belonging to the other subdivision of the pelvic lymph nodes – the visceral pelvic lymph nodes.

As the term visceral suggests, these are the nodes which directly surround and drain the organs or viscera of the pelvic cavity. They can be divided into four main groups – the paravesical nodes. the pararectal nodes, the parauterine nodes, and the paravaginal nodes, with the latter two applying to females only, of course.

In terms of the urinary system, only one of these are of real interest to us today which are the paravesical nodes, which are located around the urinary bladder. The term vesical gives a nod to the urinary bladder and the Greek prefix para meaning around or side by side. In males, these lymph nodes are also located around the prostate.

We can divide them into three groups based on their relative position to this organ – the prevesical, lateral vesical, and postvesical lymph nodes. As you can imagine, they mainly drain lymph from the bladder and from the prostate in males.

The prevesical nodes, also known as the anterior paravesical nodes, are located between the anterior surface of the bladder and pubic symphysis. The lateral vesical nodes are found close to the inferior end of the medial umbilical ligament lateral to the urinary bladder. The postvesical nodes, also known as the posterior paravesical nodes, are not visible in our illustration here, however as their name suggests, they are located along the posterior wall of the urinary bladder.

And that pretty much is as far as we're going to go with our exploration of the pelvic lymph nodes in the context of the pelvic urinary organs, so let's move back up now to the lumbar lymph nodes which are also sometimes referred to as the parietal abdominal lymph nodes.

These are a large group of nodes which surround the length of the abdominal aorta and inferior vena cava, and because of that, they can be divided into three major subgroups – the left lumbar or paraaortic lymph nodes, the intermediate or interaorticocaval lumbar lymph nodes, and the right lumbar or the paracaval lymph nodes.

The left lumbar nodes can again be further divided into three groups. The first of these are the preaortic lymph nodes located anterior to the abdominal aorta. The next are the lateral aortic lymph nodes or the lateral aortic nodes for short which as you would expect are located along the lateral border of the abdominal aorta. These are the most developed and plentiful of the paraaortic nodes.

The final group of paraaortic nodes are not visible in our illustration as they are located behind the abdominal aorta and are therefore known as the retroaortic lymph nodes, and these are the least numerous of the paraaortic members.

Like the left lumbar nodes, the right lumbar lymph nodes are divided into three groups, and once again, those anterior to the inferior vena cava are the precaval nodes which are usually three to eight in number. To the right of these are the lateral caval or laterocaval nodes which are comprised of one large node seen here at the level of aortic bifurcation which is specifically known as the inferior caval lymph node as well as two to three nodes located at the angle of the inferior vena cava and right renal vein.

Now that we have mentioned all the different members of the lumbar lymph nodes, we can finally talk about their afferent and efferent lymphatic vessels.

The afferent vessels going towards the lumbar lymph nodes are many and carry all lymph received by the common iliac nodes in addition to others which drain the suprarenal glands, the kidneys, and abdominal part of the ureters, gonads, uterine tube, and the upper part of the uterus. In addition, they can also receive lymph drained from the gastrointestinal tract, but that's the story for another tutorial. All in all, you can see that these are a pretty important group of lymph nodes.

The efferent vessels from the lumbar lymph nodes converge and will form two larger lymphatic vessels which are the right lumbar lymph trunk which drains the right lumbar nodes and its left counterpart, the left lumbar lymph trunk, which receives lymph from the left and intermediate lumbar nodes. Both are located posterior to the abdominal aorta and IVC.

The left and right lumbar lymphatic trunks join together at the level of the first and second lumbar vertebrae, sometimes, with another vessel known as the intestinal lymphatic trunk to form a larger, somewhat dilated structure known as the cisterna chyli. The cisterna chyli is very variable in its size and appearance but often looks like an elongated sac and it receives lymph from the major abdominal trunks which will continue as the thoracic duct through the thorax eventually terminating at the venous angle of the left internal jugular and subclavian veins.

Okay, you'll be happy to know that that concludes our marathon tour of lymph node groups. Let's put all of that information into context now by looking at the drainage from the perspective of each urinary organ.

So as I mentioned at the beginning of our tutorial, we have four primary organs to concern ourselves with here – the kidneys, the ureters, the urinary bladder, and of course, the urethra. Let's begin with the kidneys.

Each kidney contains a network of intrarenal lymphatic vessels which run closely with the intrarenal arteries. These lymph vessels join together to form four or five renal lymphatic trunks as you might expect at the hilum of the kidney and course alongside the renal artery and vein. On the right side, these vessels empty their contents mainly into the right lumbar and intermediate lumbar lymph nodes while on the left side, the efferent lymphatic vessels of the kidney tend to only drain into the left lumbar lymph nodes.

The lymphatic drainage of the ureters is a tiny bit more complicated in that the superior abdominal part of each ureter drains directly to the lumbar nodes while the inferior abdominal part generally drains to the common iliac nodes. The intrapelvic part of the ureters, however, are usually said to be drained by the internal iliac and paravesical nodes.

We've already become quite familiar with the lymphatic drainage of the urinary bladder when we looked at the paravesical lymph nodes which are composed of prevesical, lateral vesical, and postvesical nodes. Their efferent vessels continue mostly to the external iliac nodes. Some collectors may terminate at the internal and common iliac nodes, however, this is more the exception than the rule.

Surprisingly, the urethra has the most complex pattern of lymphatic drainage of all the urinary organs with several defined pathways draining it. For the purposes of this tutorial, however, let's just say that lymph drained from the membranous and prostatic urethra in males and the entire urethra in females is mostly received by various members of the internal and external iliac lymph node groups, be it via the paravesical nodes, the inferior gluteal nodes, the lateral sacral nodes or others.

In males, however, it's important to note that the spongy part of the urethra has a somewhat longer drainage route in that lymph is first drained to the prepubic node and superomedial superficial inguinal nodes before eventually being also received by the external iliac lymph nodes.

We've now gone through the lymphatic system relating to the urinary organs. Let's take a look at a clinical application of what we've learned today.

Knowledge of the lymphatic system plays a key role in cancer diagnosis as carcinomas may spread through the body by way of the lymphatic system. Medical imaging or biopsy of enlarged lymph nodes is one means of assessing the spread of metastatic cancer cells in the body.

In the case of bladder cancer or urothelial carcinoma, clinicians most commonly use the TNM staging system in cancer diagnosis where the T refers to the characteristics of the tumor, N relates to the lymph nodes that are involved, and M refers to the metastases to other organs.

Since we're talking about lymph nodes, let's talk at the N staging of bladder cancer. N0 means that there are no cancer cells in any lymph nodes, N1 means cancer cells have been detected in one of the pelvic lymph nodes, N2 signifies that cancer cells are present in multiple pelvic lymph nodes, and finally, N3 means that cancer cells have spread to one or more lymph nodes outside of the pelvis.

And that brings us to the end of our tutorial. Let's finish up as always with a quick summary of the lymph nodes we identified today.

At the beginning of the tutorial, we briefly went through some important terms such as describing the urinary system and the lymphatic system which transports lymph around the body and the lymph nodes which are involved with the activation, proliferation, and differentiation of the lymphocytes. Then we looked at the lymph nodes involved in the main pathway of the lymphatic drainage and discussed some organs that were drained by it – internal and external iliac lymph nodes which drain to the common iliac lymph nodes then to the paraaortic lymph nodes which are drained into the lumbar lymph trunk emptying to the cisterna chyli which is a confluence of lymph around the lower part of the body. We also had a look at smaller lymph nodes which are more directly related to the urinary organs such as the paravesical lymph nodes which are divided into the prevesical, lateral, and retrovesical lymph nodes draining the urinary bladder.

I hope you enjoyed this tutorial. Don't forget to check out more videos on our website. Thanks for watching and happy studying.