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Hi, I'm Dr. Stephen Pomeranz, talking about pediatric renal masses.

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3 00:00:04,550 --> 00:00:09,150 And this six-year-old youngster has a large mass

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in the abdomen crossing the midline, and the reason

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it's crossing the midline is in part related to the

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fact that the patient has a known horseshoe kidney.

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Now, Wilm's tumor is the most

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common pediatric renal tumor.

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90% of all pediatric renal tumors.

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Important if you're test-taking, the incidence

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is 8 per million under the age of 15.

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Now, the incidence of horseshoe kidney is

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about 1 in 400, but of all Wilm's tumors

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that occur, only about somewhere between 0.04 or 0.4 and 0.9%.

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16 00:00:42,035 --> 00:00:43,235

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18 00:00:44,025 --> 00:00:44,194 So 0.4 to 0.9% of Wilms tumors occur in horseshoe kidneys.

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20 00:00:44,745 --> 00:00:49,445

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So it's not particularly common.

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Now, this presents a particularly

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relevant diagnostic challenge.

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Which is, what is happening to the vasculature?

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Now, let's talk once again a little

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bit about staging these lesions.

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Uncommonly, these tumors extend into the renal vein or

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the IVC, or even the right heart, but it does occur.

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So when you look at this MRA and MRV,

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there's the aorta displaced, and there

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is a portion of your horseshoe kidney.

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There's at least the left portion of

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the shoe, uh, on the viewer's right.

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And here is the inferior vena cava

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with some collaterals behind it.

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And it looks, for all the world, like the tumor

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is in the inferior vena cava on the MIPT MRV.

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This is scary.

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So now we go back over to our study, and

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we see that our, our tumor, which is often

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triphasic in terms of its histologic components,

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has a lot of different components in it.

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It's got some necrosis in it, it's got

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some blood in it, it has some solid tissue

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in it, but that's not why we're here.

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We're here in this vignette to explore the status

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of the renal vein, and specifically the inferior

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vena cava is where I want to focus my, my effort.

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And going up and down, I'm, I'm not really

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sure I could clear the inferior vena cava.

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There's this satellite nodule to our lesion superiorly.

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And I'm not comfortable making that distinction

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in the coronal projection, especially

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with four or five millimeter sections.

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I'd much rather do it in the uber

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comfortable environment of an axial.

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So let's bring down an axial, and we're gonna go

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right through our area of defect, so we start

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above it, and the first thing to do is to find

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the cava, because when I look at this image, I

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might look at the aorta as an opacified structure

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and then go over here and say, oh, well there's

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the cava with a big, giant tumor defect inside,

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but I'd be wrong, and so that's why I go up high.

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I go up high to affirm the inferior vena cava.

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Now that I've got the cava in my

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sights, I'm going to work my way down.

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And my cava is just starting to get pancaked.

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Look at that thing.

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It's flattened by this big

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satellite nodule from our tumor.

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Still flattened, still flattened, still flattened.

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Now right about here, look to the right.

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This is where we would expect

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the invasion, right there.

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So let's get there.

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We're almost there.

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And it is not invaded.

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It is just simply flattened like an incredible pancake.

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There's no mass that's arising inside it expanding it.

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For it would expand if there was a tumor inside it.

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It's not expanding.

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It's contracting.

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It's flattening.

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Let's keep going down.

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And this is affirmed in other projections on

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other axials until it eventually reappears.

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And here it's now just starting to come

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back as the iliac system as we move down.

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And there it is.

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There, there are the iliac veins.

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There's the right common iliac vein.

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And once again, let's go back up.

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Let's work from the bottom up.

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Just to reaffirm our thought that it's being

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squished or compressed rather than invaded.

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If you want to take another axial

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projection, we can do that as well.

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With a slightly different pulsing sequence.

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I don't think the pulsing sequence matters that much.

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But once again you can see how you would be easily

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fooled by this satellite nodule thinking CAVA, defect

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inside, clot inside, tumor inside, and you'd be wrong.

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Let's go up a little ways.

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And this time we don't have the contrast on board.

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And look at how confusing it is.

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Here's the cava anteriorly, over here, not over here.

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So you really need the contrast

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enhanced MRV to make this diagnosis.

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Now in terms of other issues related to this huge mass

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in a horseshoe kidney, you want to evaluate adjacent

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organs, you want to evaluate the opposite kidney, you

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want to look at spread to the peritoneum, you want to

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look for metastatic disease in the lungs using MRV.

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CT, a contralateral evaluation of the

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opposite kidney, critically important,

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especially in this horseshoe kidney.

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And let's go back to our contrast enhanced MRI

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where we can corroborate the integrity of at

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least the left half of the horseshoe kidney.

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There it is.

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And see where the tumor stops and where

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the rest of the horseshoe kidney begins.

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And we have absolutely done that in this case

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and affirmed that the cava is not invaded,

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that the right heart, all the way up high,

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we could affirm is not invaded.

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We don't see any right heart invasion here and

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I'm not, I'm not going to tackle the right renal

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vein because it's, it's draped over the front of

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this lesion and that would take us a little more

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time than we have in this particular vignette.

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So cava is patent, cava compressed, horseshoe kidney.

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The left side of the horseshoe remains.

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We can separate exactly the plane between

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the lesion and the horseshoe kidney. Dr. P out.