POCUS Skin and Soft Tissue

July 29, 2021

ID6844

To CiteDCA Citation Guide

00:00Hi, my name is Julie Leviter.
00:03I'm an assistant professor of
00:04clinical Pediatrics at Yale and
00:06I'd like to talk to you today
00:08about point of care ultrasound or
00:10pocus for skin and soft tissue.
00:11So your first patient of the day
00:13is a 15 year old male with red
00:15tender lesion of his ankle as shown.
00:18Now it's not obvious to you on exam
00:20whether there is an underlying Abscess
00:22or if this is simply Cellulitis.
00:24How do we tell whether we should
00:26just give antibiotics or if we need
00:28to perform an incision and drainage?
00:30We can use focus. Here
00:32are some indications for when you
00:34would use pocus for skin and soft tissue.
00:36So the first indication is to differentiate
00:39Cellulitis versus an Abscess.
00:40Figure out if you're just going to give
00:43antibiotics or if you also need to perform
00:46a drainage procedure.
00:48The next is to identify the location
00:50and size of the Abscess that
00:53can help to direct any procedure
00:55that you're going to perform.
00:57The next is to identify the presence
00:59and location of foreign bodies,
01:01thereby helping you to remove them,
01:03and the last is too.
01:05As I mentioned before,
01:06guide your Abscess drainage
01:08and your foreign body removal.
01:12Let's talk about what skin
01:14and soft tissue focus is not meant to
01:17do. One is that it's not meant to
01:20differentiate Cellulitis versus edema.
01:22This is going to look very similar
01:24or exactly the same on ultrasound,
01:27and so you're going to have to use
01:30other clinical and historical clothes.
01:32Another thing that skin
01:33and soft tissue pocus is
01:35not meant to do is to differentiate
01:38Abscess versus hematoma.
01:39Again, these can look very similar.
01:41An ultrasound and you're going
01:43to have to go with historical
01:45and clinical cues. So
01:48how do we practically go about
01:50scanning skin and soft tissue?
01:52We're going to use a linear probe.
01:55That's because it's high frequency and
01:57we want good resolution of
01:59those superficial structures.
02:00We're also going to put a tegaderm on it.
02:04It is not cool to get the probe
02:07covered in Mersa or COVID-19.
02:09The first thing I want you to
02:11do when you start this scan is
02:14to adjust the depth and gain.
02:16You'll notice that this depth
02:18is 4 centimeters,
02:19so we're going to get great
02:22resolution of those structures.
02:23Of interest in the superficial
02:25skin and soft tissue,
02:26one rule is to start though
02:28at about 5 to 6 centimeters,
02:30and then decrease your depth to hone
02:33in on the structures of interest.
02:35Otherwise you might miss something
02:37deeper then you want to turn up your
02:40game to make sure you can visualize
02:42your object of interest with good resolution.
02:46Once you've optimized your depth and gain,
02:49I want you to fully interrogate
02:52your area of interest.
02:54Now this doesn't mean just scan the area
02:57that looks abnormal on visual inspection,
03:00fully sweep through the area because
03:02you might find an Abscess adjacent to
03:05that area that looks abnormal visually.
03:07So scan it in short axis and then
03:10rotate 90 degrees and scan in long
03:13axis and two perpendicular planes,
03:16then measure.
03:17Any kind of fluid collection in
03:20three dimensions apply color,
03:22Doppler and optionally compare
03:25to the contralateral side.
03:28So now we're ready to scan.
03:31Let's first take a look
03:33at what normal tissue looks like.
03:35Here is someone's chest wall. This very top
03:39layer is the epidermis. Then we
03:42have some fascia and subq tissues.
03:44Nicely layered hypoechoic with linear,
03:47clearly demarcated sort
03:48of facial planes in there.
03:51Then we have the deep fascia layer,
03:54a little more hyper, hyperechoic and linear.
03:57Here we have some muscle,
03:59note the striations going from left
04:02to right and then we have bone.
04:05It's echogenic with acoustic
04:08shadowing posteriorly.
04:09Here's the calf of a four year
04:12old boy with pain, redness,
04:14warmth, and induration.
04:15Does this look different
04:17from the previous slide?
04:18It should.
04:19Those nice bright white lines of
04:21the fascia layers have disappeared.
04:23Now you have this black anechoic
04:26fluid tracing within the tissue.
04:28This is called cobblestoning.
04:31How about this scam?
04:32This is a 5 year old boy with buttock pain,
04:35redness, warmth, and induration.
04:37First of all,
04:39aside from the obvious circle
04:41in the center of the screen,
04:43which we'll get to in a second,
04:46what do you make of this tissue architecture?
04:50Notice how those nice bright
04:52fascia layers have disappeared,
04:53and now it looks homogeneous,
04:56so this is caused by the inflammation
04:59and this sort of anechoic fluid
05:01collection with a heterogeneous
05:04inside that is an Abscess with pus.
05:07Take a look at this slide.
05:10Look how bright it looks posteriorly.
05:13So what artifact is this?
05:16This is called posterior
05:18acoustic enhancement,
05:19so this happens posterior
05:21to a fluid collection.
05:23Any kind anywhere in the body also occurs
05:27in the bladder and the gallbladder,
05:30but here this can help us
05:34differentiate Abscess versus
05:35Cellulitis in cases when the pus
05:38inside isn't as hypoechoic or
05:40obvious as in the previous slide.
05:47So before we spoke about
05:49to have a complete scan,
05:51we not only have to fan through
05:53in two perpendicular planes,
05:55but we also have to measure the
05:57object of interest and apply color.
06:00So let's talk about that right now.
06:03So here is an illustration of how
06:06we need to measure our object
06:08of interest in three planes.
06:10So here on the top of Mount Upper
06:13left you see depth and width
06:15measured and then in the bottom
06:18right we're measuring the length.
06:24Here we are applying color Doppler.
06:27Now this is important to
06:30distinguish this structure from,
06:32for example, a blood vessel,
06:34a lymphatic structure,
06:36even a pseudo aneurysm or a mess.
06:39All of these potential alternative
06:42diagnosis would be expected to have
06:45some flow and should definitely
06:48not be incised as you would and.
06:51Abscess another thing that you can do
06:55to differentiate is to apply pressure
06:57and look for the swirl sign or the
07:00movement of the contents inside.
07:03So this will happen in an Abscess and
07:05it won't happen in a lymph node or
07:08mass or pseudo aneurysm or lymphatic
07:11malformation or something like that.
07:16So let's talk a little bit more about
07:20some of these potential pitfalls.
07:22So is this an Abscess?
07:24No, this is a lymph node.
07:26How can we distinguish this from an Abscess?
07:29Will usually it's more Oval or round.
07:32Morse well circumscribed, it doesn't
07:34swirl on compression,
07:36and you can see this hilar vascularity
07:39that will light up with color Doppler.
07:43How about this one? Is this an Abscess?
07:46You might see some pockets of
07:49hypoechoic fluid, but not as much
07:52as you would see in an Abscess,
07:55and there is some blood flow,
07:58whereas we would expect an Abscess
08:00not to have blood flow through it.
08:03So this is a lymphatic malformation,
08:06something you definitely would not
08:08want to incise and would want to
08:12follow up with radiology. Study.
08:14Now, before applying color Doppler,
08:17we might have misdiagnosed this
08:19person with an Abscess as well,
08:21but now that we've applied color Doppler,
08:24we can see what's called the Ying
08:26Yang sign of a pseudo aneurysm.
08:28Again, not something that we want to inside.
08:33So here's a case.
08:34We have a 10 year old girl
08:37with a breast Abscess.
08:39It was actually seen at an outside hospital.
08:42They performed an Ind,
08:43but it didn't reveal any pus,
08:46just some blood and they were transferred.
08:48Now to your hospital or for
08:51some further management.
08:52So when you apply your ultrasound,
08:54you notice that the pocket of fluid does
08:58not correlate with where it might seem
09:00that there was an underlying Abscess.
09:03On visual and physical exam.
09:07So this has been found in the
09:10literature to be true as well.
09:13This was a prospective randomized
09:15clinical trial of patients in an
09:17academic emergency department.
09:19Patients presenting with an
09:20uncomplicated skin soft tissue,
09:22Abscess requiring drainage diagnosis
09:24was either by physical exam by
09:27bedside ultrasound or by both and
09:29those randomized to the pocus group
09:31had Ind performed with bedside
09:33ultrasonographic imaging of the Abscess.
09:35Those in the non pocus.
09:38Group had Ind with physical exam alone.
09:41Now there were 125 patients
09:43enrolled 54 in the focus group and
09:4753 in the non focus group.
09:49They found that the Pokus group
09:52was less likely to fail therapy.
09:54The focus group had a four point 8%
09:58failure rate and the physical exam
10:01group alone had a 16% failure rate,
10:04so this is likely because pocus guidance
10:08facilitates the identification of the
10:10Abscess pocket and allows for better
10:13planning of the initial incision.
10:16So,
10:16just to recap,
10:17the first thing we want to do when we're
10:20doing a skin and soft tissue ultrasound
10:23is cover the probe with a tegaderm.
10:25Then we're going to scan in two planes,
10:28fully interrogate the area of interest we're
10:31going to measure the dimensions in 3D,
10:33apply color Doppler check for the swirl sign,
10:36and don't be fooled.
10:37If anything doesn't look like you would
10:40expect an Abscess to look like and has
10:43any other signs like color flow through it.
10:46Then be sure to follow up
10:50with radio radiologic imaging.
10:52Let's talk next about using
10:54ultrasound for foreign bodies.
10:56It actually has a fantastic
10:58sensitivity of 80 to 90%.
11:00It's very useful for finding
11:02radiolucent foreign bodies like wood,
11:04plastic, and cactus spine.
11:06But remember,
11:06if you don't
11:08see the foreign body that you're
11:10looking for on ultrasound,
11:12make sure to get an X ray just to
11:16make sure that nothing is missed.
11:19And remember. Pocus is also useful in
11:22real time for foreign body removal.
11:30So what do you see here?
11:34So at the top of the screen you see
11:36a hyperechoic linear structure that
11:38doesn't look like it's part of the
11:42muscle tissue that we're seeing here.
11:44This is a retained needle.
11:48This next patient is a 5 year
11:50old boy with a red tender area
11:52on the bottom of his foot.
11:53What do you see?
11:56So where are these arrows are pointing?
11:59Are the two perpendicular
12:00views of a retained splinter,
12:02so also notice that there is a small
12:05anechoic rim as well as some other
12:08pockets of fluid that we're seeing.
12:11Superficially this is likely some
12:13fluid or pus that's collected
12:15around the splinter plus adima or
12:17Cellulitis based on the ultrasound
12:19findings and clinical context.
12:21I'm thinking this splinter needs
12:23to be removed and that this kid.
12:26Needs antibiotics after removing
12:28the foreign body makes sure
12:30to scan again to ensure that
12:33you've removed the whole thing.
12:36This is a nice example of two
12:38artifacts that are frequently
12:40seen with foreign bodies,
12:42so the first is reverberation artifact.
12:45So this happens when there are two
12:47reflectors parallel to each other and
12:50perpendicular to the ultrasound wave and
12:52the sound gets trapped between these
12:55two echogenic surfaces bounces back
12:57and forth before returning to the probe.
13:00So since it takes more time to get back,
13:04it seems that.
13:05Each successive bounce
13:07comes from a deeper place,
13:09so that's where you're seeing
13:11that sort of triangular cone of
13:14brightness posterior to that object.
13:17That's more superficial.
13:20So the other artifact that we're
13:22seeing here is acoustic shadow.
13:25That's all that black area behind
13:27the object up on top of the screen,
13:31and that's because the object is preventing
13:34the sound waves from passing through.
13:36So this example shows a chemotherapy
13:39port so it didn't get there by accident.
13:43But I thought this was a really
13:45nice example of both reverberation
13:48artifact and acoustic shadowing.
13:50Both of which you can see
13:52with foreign bodies.
13:55So here's one last example.
13:57This is an 8 year old girl
14:01with a red painful earlobe.
14:03So look at whether it where
14:06this arrow is pointing.
14:08There's a hyperechoic structure
14:10at the top of the screen that is
14:13in Piper echoic metal earring,
14:16and this also shows that nice
14:18posterior acoustic shadowing
14:19and reverberation artifact.