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I'm Dr. P,

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3 00:00:01,470 --> 00:00:03,940 back with our discussion of pediatric renal masses.

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In our patient that has a pediatric Wilms tumor,

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the most common primary tumor in young pediatric patients.

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And let me show you the claw sign real

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quickly since it's demonstrated nicely here.

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I'm going to draw over our tumor, and you can see kind of

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a capsule or pseudocapsule around the tumor.

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And then I'll color in the kidney right next to it.

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There's the kidney right next to it.

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And it does make a little bit of a

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claw, especially on the medial side.

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Not so much on the lateral side.

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So that's nicely illustrated.

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We've got an in-phase, uh, GRE T1.

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An out-of-phase, uh, GRE T1

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in the middle, and this one demonstrates the India ink

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sign, which is indicative of an out-of-phase image.

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And on the right, we've got a

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T2 spin echo with fat suppression.

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So let's look at some of the signal

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intensities that can be generated here.

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Uh, we know that Wilms tumors can contain fat.

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In this case, not so much.

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But we do have blood.

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In fact, we had a lot of blood in the

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capsular area, which you'll get to see again.

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But there's also some blood elsewhere.

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For instance, we've got, uh, our

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GREs don't really show that much.

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Maybe a little bit of hyperintensity.

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But when you get to the T2, we've got some more fresher

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looking blood right here on the T2 spin echo,

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the so-called deoxy and intracellular methemoglobin effect.

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And we've also got this little dot right there.

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At least part, a portion of that dot.

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I'll blow it up and make it a little bigger.

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It's pretty black right there.

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And it's still black in the out-of-phase.

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And it is still black,

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if I can match it up right there.

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It is still black on the T2 image.

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So black, black, and black.

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That's a little focus of calcification.

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We know that calcification occurs about

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85% of the time in neuroblastoma.

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About 15% of the time in Wilms' tumors.

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50 00:02:04,255 --> 00:02:07,055 Now, fat, although it's not present prominently

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in this particular case, can occur in renal cell

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carcinoma and, as you know, AML or angiomyolipoma.

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So, it is not unique to Wilms' tumors

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or any one of those, those three tumors.

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Now, let's scroll a little bit

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and take a look at our renal vein.

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There's a tiny bit of signal in our renal vein, and

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that means you may have to drill a little bit more

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deeply, use MRV, which we did here a little bit later.

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You might look at some of the other

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sequences to see if the vein is expanded.

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It is not expanded.

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This is flow phenomenon in the renal vein.

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Um, it's a little bit gray on the gradient

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echo images, but you should be worried

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about that and explore it even further.

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We were able to clear the renal vein in

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this particular case, but expansion of the

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renal vein can be a very important finding.

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For involvement of the renal vein, pushes you

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towards the diagnosis of Wilms' tumor, and I do use

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axial thin section imaging for that particular

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diagnosis, and again, you may have to resort to MRV.

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Just a word about Wilms' tumor.

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Wilms' tumor arises from mesodermal precursors of

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the renal parenchyma, known as the metanephros.

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It accounts for at least 90% of pediatric

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renal tumors, and in the United States, there

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are 7 to 8 cases of Wilms' tumor per million

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children that are younger than 15 years annually.

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Total number of new cases is estimated

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at about 500 per year, so not that many.

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But 75% to 80% of cases occur in children 5

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years of age or younger, at the peak, 2 to 3 years

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of age, which overlaps with neuroblastoma, a very

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important differential diagnostic consideration.

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Let's move on, shall we?