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Dr. P here.

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3 00:00:01,640 --> 00:00:05,550 This is a 53-year-old male with diffuse

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swelling and erythema, a warm foot, and we've

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got a sagittal, heavily water-weighted image

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on the far left, the so-called lateral view,

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and then a sagittal T1 fat-weighted image in

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the center, and then on the far right, another

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heavily water-weighted image in a long axis

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axial-type projection.

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So it's obvious to many of you

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that the entire foot is swollen.

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Look at this laminar pattern

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of interstitial edema.

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Just about everywhere.

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You've got some tendons interspersed

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there, and then you look a little bit more

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deeply, you see the same phenomenon here.

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Here's a couple blood vessels

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working their way around, and then you look in

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the superficial soft tissues, and this patient did

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have, as you can see on the far right, a focal

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ulceration along the lateral aspect of the foot.

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So that is of some concern.

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And then when we get into these areas right

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here, you know, you'd like to think they're

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veins, but you can't hook them all up.

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And that's one of your jobs is to follow

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them around and make sure they're nerves

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or veins or fascia layers or maybe

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just fat that's been fat suppressed.

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And you have to go back and

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forth to kind of figure that out.

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And when you go over here and you look inside

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this ulcer, if nothing else, if you don't believe

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that any of these areas could be gas, and that

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is an essential thing to rule out in a patient

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who has fasciitis or myofasciitis, then,

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you know, you can always go to, you know, say,

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CT or some other modality if you're unsure.

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So we're scrolling around.

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The T1 is not particularly revealing as it usually

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isn't for air or gas unless it's a lot of it.

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When we go to the water-weighted image,

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these are not structures that are linear.

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These are not structures

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that are connected to veins.

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So, they look like little tiny dots of

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hypointensity, and you must at least

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be very worried about gas bubbles.

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So then, you know, you can justifiably get a CT.

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And a CT was done.

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There's no shame whatsoever in confirming or

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corroborating the diagnosis of air or gas with CT.

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And indeed, it's obvious, we do have air or gas.

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So CT doesn't do as well at showing abscesses,

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the myositis, the laminar fasciitis that's

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occurred, but it does better, it does a very good job

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at picking up air or gas.

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So let's talk a little bit about this

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entity of flesh-eating bacterial infection

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that is caused by group A Streptococcus.

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Yes, you can get Clostridium.

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Yes, you can get other organisms involved,

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especially when there's gas.

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It's a strange thing.

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It doesn't take a lot of trauma. You know, I've

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seen it happen with somebody that just got a

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little abrasion from brushing their arm against

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a rock while on a trip, a rafting

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trip in Georgia. I've seen it many, many times

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with innocuous injuries. Somebody that got

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stuck with a toothpick and that's it.

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I've seen it as a result of an infected

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chickenpox, which sounds kind

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of crazy, but there's a name for that.

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I'll tell you in a minute.

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So trauma plus often, not always, but often some

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degree of immunosuppression: diabetes, alcoholism,

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chronic renal failure, steroids, drug use, HIV.

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Now, the chickenpox type, where you get it

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with chickenpox, is called varicella gangrenosa.

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That's a rarity, that's just a

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piece of trivia to win a beer at a bar.

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But toxic shock syndrome occurs about

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10% of the time in this entity.

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Now typically on physical exam, you, you might

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see crepitus or feel crepitus, not see it.

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Feel it or you might not.

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You might see purplish discoloration of

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the skin that's dusky or patchy.

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You might not.

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You might see some of the cardinal

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lab features of necrotizing fasciitis.

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One of which is often not quoted

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or recognized, hyponatremia.

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You may also see an elevated BUN and the

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white count may or may not be elevated.

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Typically, there's deep laminar enhancement within

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the interstitium of the muscle, but you know what?

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You can see that with just a straightforward

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myositis, and you can see it with, you know,

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other forms of myositis, including those

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related to immune types of disorders.

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The differential diagnosis in a case like

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this is going to be cellulitis, but that's

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disease here in the subcutaneous region.

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Once you get into the muscle,

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now you're into myofasciitis.

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You can get simple pyomyositis,

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in which you get an abscess in the

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muscle without necrotizing fasciitis.

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You can get lymphangitis.

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You can get idiopathic inflammatory myositis.

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You know, some of the other important differential

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diagnoses, especially when out of the foot,

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but also in the foot, include ischemia, compartment

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syndrome, rhabdomyolysis with myoglobinuria.

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So a case like this, you want to

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get a urine myoglobin, you want to check

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the CPK, you want to check the aldolase,

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you probably want to check the ALK Phos, and

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some other key measurements of myonecrosis.

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Lymphedema is usually more superficial.

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126 00:05:31,915 --> 00:05:34,305 It's usually not as deep within

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the interstitium of the muscle.

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And the same thing is true of venoedema

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or venous edema from venous obstruction.

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The fluid tends to congregate around the venous

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structures like this, which is not happening here.

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You know, it's just randomly

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going from proximal to distal.

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And finally, you can get some inflamed, ruptured,

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capsulocinovial cysts that dissect into the foot.

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And I've seen that happen.

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And I've also seen primary

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thrombophlebitis in one of my good friends

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occur in the foot and look a little

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scary with some edema in the deep

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aspect of the muscular tissue.

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So this is necrotizing fasciitis.

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I know you're all familiar with it and

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that it can occur in various other parts

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of the body, especially in the perineum,

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where it can be particularly difficult

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to manage and particularly heinous.

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It's a case that sometimes presents

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to the ER and everybody is scrambling.

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Necrotizing fasciitis.

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Dr. P out.