Examination of the Lymphatic System

00:01 All right, next up, we're going to talk about the lymphatic system.

00:04 It turns out the lymphatic system is composed of over 400 lymph nodes scattered throughout the body in different regions.

00:11 I promise you, we're not going to go through every one of those 400 lymph nodes.

00:16 We're going to go through a couple specific regions.

00:18 It turns out that only about 100 of those lymph nodes are even palpable under normal circumstances.

00:23 The majority of them are buried deep within the thorax or in the abdomen and can really only be visualized with radiologic imaging.

00:31 The second thing I'll say about the lymphatic system is that all those lymph nodes are draining in very predictable ways, draining back into the venous system ultimately.

00:38 So the left side of the body, for the most part, is going to drain into your left sided subclavian and internal jugular vein on the left.

00:46 And the right side of your body is going to drain into the equivalent vessels on the right, with a very important exception involving the lower half of the body, which we'll come to later.

00:55 But first off, if we're having a patient who had, let's say, an upper respiratory infection, we would start off by examining the head and the neck lymph nodes.

01:03 So let's jump into those systems now.

01:06 So first place we'll start off with is looking underneath the mandible.

01:09 So we're going to feel the lymph nodes underneath the mandible here.

01:14 Then we'll move on to the anterior cervical chain.

01:18 These lymph nodes are going to be felt just in front of the sternocleidomastoid muscle and we'll actually dive deep to the sternocleidomastoid muscle.

01:27 Then we have posterior cervical chain lymph nodes.

01:29 These are going to be felt behind their sternocleidomastoid muscles.

01:34 We have preuricular lymph nodes.

01:36 We have posterior auricular lymph nodes as well.

01:39 And lastly, we have occipital lymph nodes back here at the occiput.

01:45 All those lymph nodes on the left side of the face are going to drain into the left internal jugular vein.

01:50 All right.

01:51 So now let's move on and take a look at the arms.

01:54 So with the upper extremities, there's only really two significant places you're going to find lymph nodes.

01:58 You're going to start off, if I may have your hand on.

02:01 You're going to find what's called the epitrochlear lymph nodes.

02:04 These are located just proximal and anterior to your medial condyles.

02:09 You can feel it.

02:10 You could feel the area where they would be if they were inflamed, sort of at the base of the biceps muscle or brachioradialis muscle down here.

02:17 You can imagine that if somebody had an acute paronychia or cellulitis in the forearm, this is where you might find evidence of inflammation and infection.

02:25 The next place is the axilla.

02:27 Now, we'd like to think of the axilla or the armpit as a box with an anterior, posterior, a lateral and medial side, and I'd like to examine each side in order.

02:37 So I'm going to start off by first examining the medial side or the side that's abutting the chest wall, then the anterior side, which is where you're going to feel the pectoralis muscles and you're looking for lymph nodes buried in that area.

02:49 Then the lateral wall underneath where the humerus is inserting and then the posterior wall where the latissimus dorsi muscles are located.

02:59 So that's the entirety of the axilla and the epitrochlear nodes.

03:04 Those nodes are also going to drain directly into your left subclavian on this side and your right subclavian onto the other side.

03:10 Now, let's move off and start examining the lower extremities.

03:13 All right.

03:14 So a moment ago, we talked about how the left side of the body in general is going to drain into your left IJ and and left subclavian vein as well.

03:23 And the right side will drain into the contralateral side.

03:25 The exception starts with the legs.

03:28 And so it turns out that both the left leg and the right leg, lymphatic system is going to converge into something called the chyle cistern, which is just to the right of the aorta.

03:39 And then that's going to form the start of the thoracic ducked.

03:42 The thoracic duct is going to march all the way up in the retroperitoneal space.

03:46 Ultimately, it's going to converge in one place in entering into the left subclavian.

03:52 And along the way, it's taking the lymphatic drainage from the entire abdomen and most of the lymph lymph nodes in the chest as well.

04:00 So the bottom line is that while everything else is pretty symmetric with the upper extremities draining to both sides and the left and right side of the head draining to both sides, the legs in the abdomen are exclusively draining via the thoracic duct into one place on the left side.

04:15 And that has some significance when we think about different cancers in the abdomen manifesting with left-sided lymphadenopathy, particularly in the supraclavicular space.

04:26 But let's take a look at the lymph node regions in the legs.

04:29 First, there's really only two spots in the legs that we look for lymph nodes and they're both in the inguinal region.

04:36 There's a horizontal field and a vertical field for the inguinal lymph nodes.

04:40 So let's take a look.

04:42 So the inguinal lymph nodes of the horizontal plane, if I'm going to just pull this down here, basically run along the inguinal ligament.

04:51 They're going to run from about the anterior superior iliac spine towards the pubic symphysis.

04:55 And in this area, you can palpate that strand of the inguinal ligament.

05:00 As you're going down, you're looking for any swelling, any swollen lymph nodes in those areas.

05:06 Oftentimes in this horizontal chain, which is draining the groin, you may find what's called "shotty lymphadenopathy", which refers to buck shot, which is the little pellets that are inside a shotgun shell.

05:17 And it's very common and has no really significant pathology associated with it.

05:24 The next part of the lymphatic drainage system of the leg is actually the vertical chain.

05:29 Now, the vertical chain is best demonstrated here.

05:32 It actually runs along the saphenous vein, the greater saphenous vein.

05:36 And this is actually what's draining the leg.

05:38 The horizontal chain is draining the groin.

05:41 The vertical chain is going to drain the leg.

05:43 And that would be palpated if it was going to be present along the greater saphenous vein in this location here.

05:51 So that's the lymphatic drainage for the legs.

05:53 And again, they're going to converge form the thoracic duct with the abdominal and fat lymph nodes and head all the way up to the insertion of the thoracic duct in the left subclavian vein.

06:06 All right.

06:06 So having talked about the different regions where we can find these lymph nodes, let's talk about some of the things we're looking for when we find a lymph node.

06:14 What are the features that are going to distinguish between a pathologic concerning lymph node for something that's more benign or associated with a transient problem like an infection? So if I were to find a lymph node here on Sean's neck in the anterior cervical chain, I'm going to be looking for a couple significant properties.

06:32 How big is the node? I know that's less than 1 or 2 centimeters in size.

06:36 It's not something I'm going to be very worried about.

06:39 Is it symmetric? If I'm finding lymph nodes scattered throughout multiple fields on both sides, that may be concerning.

06:45 If somebody has a breast lump and I find lymph nodes just in the axillary chain on one side, that would be concerning as well.

06:52 So thinking about sometimes asymmetry is important, sometimes symmetry is important.

06:57 The next feature is whether it's mobile or not.

07:00 If I find in his axilla, for example, a lymph node that is 2-3 centimeters in size and it's fixed to the deeper tissues, that is I can feel it, It's firm, it's rubbery, and I can't really move it around.

07:13 It's as if it's fixed in place.

07:15 That is a very significant feature that may suggest something like cancer, for example, particularly in the axilla of breast cancer.

07:24 And the last feature is really is it tender or not? Typically, if somebody has, for example, strep throat with an acute infectious pharyngitis, I may find multiple lymph nodes in these anterior cervical chains.

07:36 And the characteristic feature that the patient would tell me is that they're really painful and certainly tender to the touch.

07:42 So tender lymph nodes more likely to be infectious in origin, nontender lymph nodes, I'm more worried about some indolent process.

07:50 And the patient will also tell me in terms of the timing of these lymph nodes, if they developed over the span of a few days, in the setting of a fever in pharyngitis, I'm not going to be as worried about them compared with the lymph nodes that the patient reports have been slowly growing over the span of weeks to months.

08:06 So that really summarizes the key features we're looking for once we find some lymph nodes anywhere in the body.