All right, thank you. Doctor Hearth. Okay, I'm gonna set it. I'm gonna set my own timer here. How long do I have? 15. Oh boy. Okay. So why do we do venus duplex? So mostly because we're concerned about DVT. Um So patients with unilateral uh extremity swelling, but also sometimes acute bilateral leg swelling. So we see this if the Kaveh is occluded, patients with limb pain or a tender palpable cord. Um It's certainly appropriate if a patient has a pulmonary embolism to get um venus duplex or if we suspect superficial thrombosis phlebitis and if we're doing surveillance, so a calf DVT that we've elected not to anti coagulate or for um suspected compression syndromes like may turner syndrome or the thoracic outlet syndrome. I'm not gonna go over anatomy except to say that it's really important that we know are deep veins from our superficial veins. So I can't tell you how many times I've had somebody tell me that someone had a basilica DVt. Uh And that is not a DVT and it has implications for treatment. Um So we don't want to anti coagulate someone typically for that kind of rhombus. So it's just that's really important and then it's also important to know proximal from distal in the leg because proximal DVT s may have a different prognosis from distal DVT? Um I do like to review this leg because it really helps me when I'm reading. So um looking at the anatomical relationships in the leg in the thigh and the leg. So um you can see here, the picture on the left is at the groin close to where we typically start our ultrasounds and you can see the two structures on the left of the street screen are the superficial femoral and the deep femoral arteries. The common femoral vein is always medial and then sometimes you'll catch the great staff in this vein draining into the common femoral vein and that produces the mickey mouse sign. Um So this is a great landmark when you're reading an ultrasound as we move into the thigh. Um Often we don't see the profound ephemeral. We may see it very proximal but oftentimes we don't image it um in the thigh the superficial femoral artery is on top and the vein is on the bottom. And I will remind us never to call it the superficial femoral vein even though it corresponds with a superficial femoral artery. Because mistakes get made that way in treating people, it's not a superficial vein. Okay, so at the knee, in the pop a little Fassa, the vein does not switch position but our transducer switches position and so the pop a little vein is going to be on the top and the pop a little artery is going to be on the bottom and then in the calf usually see the posterior tibial veins tucked up under the gas truck muscle and then more deep to that the paired peroneal veins. So when we think about veins, what do they look like. So veins um the lumen should be echo free. Although our ultrasound nowadays is so good that there's often faint echo, Jenise itty um in the lumen because we're seeing the reflection of red blood cells. And if we have very slow flow sometimes we'll see a big reflection of red blood cells. Um The wall of the vein is usually invisible because it's very thin unlike an artery which has several layers and a muscle. And you can see here on this screen the artery is to the right and I can see a tiny intimate reflection. Whereas the vein I just really don't see a vein well at all. Now in patients who've had DVT in the past, that vein wall may become thick. Um And we can see that on ultrasound. And then veins in the legs often have valves and we may if our imaging is really good c valves and it's actually really cool to see them flapping in the breeze. Um And these the number increases from proximal to distal typically. So most importantly on grayscale veins are compressible. So because veins have very thin walls um they're held open only by the pressure of the blood in the lumen. And so we should be able to compress them easily when we obtain compression images. This is always in the transverse view. So if you're pushing on a vein in a longitudinal view, that vein may slip out of your field of view and you could interpret that as a compressible vessel when in fact you're just not seeing the vessel. Um When we diagnose DVT compress, compress ability is the single most important criterion. So if we cannot compress a vein we cannot rule out DVT. And typically a vein that's non compressible has a DVT. There are some exceptions but um in general. So here we can see the digital external iliac vein. So on the left of your screen um is a non compression image. On the right is a compression image. And on the left side we can see the um external iliac artery medial to that as the external iliac vein. I could see a little bit of echoes in the lumen. But you can see on the right frame when all that stuff gets squished, That vein is gone. Now there's some gunk or schmutz. Um that's for dr leaders under there. That's not that's not vain. It's just some some echo Jenness city. And um where I used to work, we always call that tissue. So on gray scale veins are usually somewhat larger than the corresponding artery. Um They can change with respiration even on gray scale if we're patient and we want to look for it. So large veins like the femoral vein will increase in size with deep inspiration or the val salva maneuver if the vein is substantially larger than the artery and its size does not change with respiration suspect rhombus although this is not how we typically diagnose him. We use. So we talked about duplex ultrasound earlier. So Doppler is important. It's an important adjunct to what we're looking for. So veins should have spontaneous flow. So in the medium and large veins of the thigh if they're normal, there's no extensive compression. We should see spontaneous flow even when the leg is dangling down. We often don't see this in the caffeine's, they're small, they're far away. Um And so spontaneous float. Usually we don't, you know, we're not Doppler during the caffeine's on an ultrasound veins should be respirator physic. So the flow velocity changes in response to respiration in the legs. When I take a breath in flow goes down. Um It's the opposite in the arms. Um We can also see this on the spectrum. Um On color flow and through the audible signal if phases. Itty is absent. So you just see a line all the way across that's called continuous or mono physic flow. And that means something is going on north of where you're looking. So you're either occluded obstructed, compressed. Something's going on there. We need more investigation. So you can see here a normal spontaneous respiration aphasic waveform. Um So where the flow is lower, that's the patient taking a breath where it's picking up is where they are breathing out and then that's probably an augmentation wave that we're seeing which we'll talk about in a moment in contrast. You can see a vein with mono physic flow. So something is going on here north of where my probe is. I imagine this person probably has a DVt and probably had a DVt in the past because that looks kind of chronic key to me. Um And so we need more investigation here. We can see away form that's really spontaneous and in fact it's pulse, it'll. And in the leg this is not normal. It reflects elevated filling pressures in the heart. And so this might be a patient with pulmonary hypertension. They may have congestive heart failure, they may be completely volume overloaded. This is not normal in the leg. This is a fairly typical waveform for the subclavian vein though. So the arms tend to be more pulse. It'll and then that's just absent flow. In someone with a Dvt. So augmentation. What is this? An augmentation, don't let it fool you into thinking, flow is respirator physic augmentation is where we compress the limb distal to where our probe is. So we have our probe here. We squeeze here. If we don't see augmentation over here, something is going on here. So there's some kind of obstruction. Now. In our lab we do whole egg ultrasound. We compress every 1 to 2 centimeters. So we're going to find what that is. But if you were doing two point or three point ultrasound and you saw a wave form like that um you would want to know more augmentation can be normal. If you have thrombosis if it's not inclusive or your well collateralized. Um I don't know why that waveform is. Oh I'm going backwards that's why. Um. Okay. So how do we diagnose acute DVt? So I mentioned non compressibility. That's really the key. So the vein must disappear completely. Um Or you cannot rule out DVT. Now sometimes things can interfere with how we compress. So uh there may be a lot of edema. There may be some muscle that's preventing us from compressing or a bone maybe in the way. And our ultrasound text usually will move around that and change position. Also a patient who's in pain um made tense when you push. Um And so that can prevent compression. A rule of thumb is if you can deform the artery and the vein doesn't compress that's a problem. So if you are pushing hard enough to deform an artery, a vein will compress a normal vein will compress. Um You don't have to deform the artery. The patients don't like it. Other things that help us diagnose acute DVt. So um the vein is often distended. So veins are very compliant their capacitance vessels. If I feel a vein with rhombus it's gonna stretch stretch stretch stretch to try to get blood past that occlusion and so usually the vein is going to be in an acute DVT is going to be much larger than the adjacent artery. However if your thrombosis non inclusive. The vein may not be dilated, ACUTE DVT is typically low echo Jenness city. It's often homogeneous and lightly speckled. And that echo Jenness city increases as the thrombosis ages, acute rhombus are Sinatra furs will tell us feels kind of squishy and spongy. It may be poorly adherent to the vessel wall, it may have a free floating uh mobile tail that you can see. That looks scary on ultrasound. And then usually for an inclusive DVc T. We'll see absence of color filling um or absence of flow Or we may see that mono physic flow. And so here you can see a dilated, left, external iliac vein. It's on the left of your screen because the vein is medial. You can see the smaller artery and when we push it doesn't compress it all and you can actually see some of that rhombus in there. When we push here's a common femoral vein DVT that's a little maybe a little bit older but still acute because that vein is very dilated. So and virtually non compressible. So another acute proximal DVT. So how do we diagnose old DVt? So and and the preferred terminology is chronic post traumatic change. So we don't confuse our ordering providers who hear the word DVT and think oh gosh I gotta anti coagulate this patient. So chronic post traumatic change. The vein is typically partially compressible. It's not distended. The thrombosis is organized and it's not really thrombosis anymore. It's more like a scar, it can be brightly echo genic, it's heterogeneous. Oftentimes it'll be linear or striated or look like a web. You may actually see some really bright white, almost calcified looking stuff if the vein is chronically occluded, which we see this sometimes too uh it's not distended. Um And it may be quite small and shrunken like actually a tragic um And it feels firmer with probe pressure. So here you can see a common femoral, that helpful arrow showing you a really bright um little blip in that vein wall that vein is not dilated at all. It compresses nearly completely. Um This is a really great picture on a lot of pictures. We might actually even miss this depending on how good our resolution is and how you know what the patient's body habits is. Like Here you can see a public um I think it's a femoral vein uh deep to the artery. With that um linear structure that's not too veins. That's uh some adherent chronic post robotic change on the on the wall of the vessel. And this is a very classic picture of chronic post robotic change. I mentioned the normal venus wave forms in the subclavian. So sometimes we'll see things, these compression syndromes. So um venus thoracic outlet syndrome when you move the arm, you completely cut off flow. May turner. I didn't put a picture in here but typically we'll see a mono physic flow in the affected in the left leg. So limitations of ultrasound body habits. So we mentioned earlier, resolution decreases as penetration increases. And so in people who are very large or very swollen we get sub optimal images. Um We can have difficulties with compression, as I mentioned before. Things like adam, a bone muscle, also the adductor canal. So sometimes the technologist will move into the back of the leg and squeeze the front of the leg to to be able to find that um distal femoral distal femoral vein veins may be duplicated. So particularly the femoral or the pop little. And this is a problem if you see only one vein and the other vein has thrombosis and you don't see the vein that has three rhombus. Um You should suspect it if your veins are really small. We also know of course the limits of the pelvis, so that iliac vessels dive into the pelvis as we get north of the inguinal ligament and they they're really hard to see. And so we may need alternative imaging modalities. And then finally, in the Caffeine's it can be tough to tell the age of three Rhombus, particularly if it's somewhere in between here, you can see on the left, a patient uh where body habit is is is a problem. So we're just losing all resolution and on the right is just an example of a normal duplicated vein, The upper extremity. Um I just want to call out the nerve bundle pitfall. So there's a nerve bundle that travels near the break your veins. And if you don't see both your paired break your veins you may mistake this for a D. V. T. And I've actually seen this in clinical practice a couple times where somebody got anti coagulated for their nerve bundle. So to summarize lack of compressibility is the most important criterion for diagnosing DVt fresh thrombosis fatally eca genic. So visualizing and apparently patent vein is not enough to rule out DVt chronic post traumatic changes often brightly echo genic partially compressible and the vein is not distended. And if you see mono physic flow you need imaging of your more proximal veins. Thank you. Mhm.
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