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I'm Dr. Stephen Pomeranz talking about pediatric renal masses. 2 00:00:01,640 --> 00:00:05,820

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And I've got a five-year-old whose parents

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incidentally discovered an abdominal

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mass while playing with their child.

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Um, on the left is a coronal T1 weighted image.

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In the middle, a coronal T2 weighted image.

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And on the far right, with exuberant fat

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suppression, is a sagittal T2 weighted image.

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Now, if we do a little scrolling here, it is

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obvious that there is a large mass in the right

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mid abdomen, and most of you would ascertain that

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this mass is associated with the right kidney.

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There are several components to the mass.

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There's a very low signal component on the T2 at the

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top, and we see it here on the T1 weighted image.

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More gray.

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We've got a more solid appearance to the

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mass, inferiorly, and it is gray on the T1.

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It is light gray or slightly hyperintense on the T2.

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And then we see what looks like

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more renal parenchyma.

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If we go to the exuberant fat suppressed image,

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we see the renal parenchyma, portions of our solid

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mass, and this very low signal area that appears to

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surround the kidney, perhaps in the renal capsule.

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So in a five-year-old, what would you think of?

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Well, under age ten, you really have

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to think about Wilm's tumor, which we'll talk about

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in a minute in terms of demographics and commonality.

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That is a renal tumor, but the

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most important differential diagnostic

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consideration in a young patient five years

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of age or younger would be neuroblastoma.

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Neuroblastoma and Wilm's tumor

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occur in very young individuals.

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Under age ten, in fact, neuroblastoma around age two.

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And we'll see Wilm's tumor in a similar

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age range and a similar location.

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But, neuroblastoma arises from the adrenal gland.

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So, the fact that our mass is centered down below,

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and we have this perirenal area up above, that doesn't

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have a shape reminiscent at all of an adrenal lesion,

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Also, when you're looking at a mass arising

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from the kidney, sometimes the claw sign is helpful.

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In other words, you have a mass.

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Here's our mass right here.

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And the kidney is seen as a

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claw wrapping around the mass.

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And we do have that here.

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Here's our claw.

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As they say when you're playing with kids, the claw.

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So we've got that present here, which

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also favors this as a primary renal mass.

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Now rarely, Wilm's tumor can

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arise in extra-adrenal sites.

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And determining the site of origin, we're

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starting basic, helps in developing an

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appropriate differential diagnosis, along with

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identifying the claw sign, and in the axial

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projection, and perhaps in the coronal projection,

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identifying the adrenal glands.

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Now features that would push you towards neuroblastoma

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rather than Wilms tumor would include calcification,

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we'll see Wilms tumor calcifies, but neuroblastoma

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much more commonly, about 85% of neuroblastomas calcify

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on CT versus about 15 percent of Wilms tumor cases.

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Tumor encasement of vessels occurs in neuroblastoma

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versus displacement or invasion with Wilms tumor.

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Let's see if we can spot a renal

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vein, and we can right there.

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That renal vein is displaced; this one

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is not invaded, and it is not encased.

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So that favors the diagnosis of Wilms tumor.

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Crossing of the midline, which we do not have

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here, also favors the diagnosis of neuroblastoma.

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Now, you might have nodes, but that doesn't

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necessarily count as direct crossing.

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Let's go over to our sagittal projection and

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see if our solid tumor is crossing the midline.

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And it certainly doesn't look like it is.

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The spine also looks clean in

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terms of metastatic disease.

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Also, extension behind the aorta through neural

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foramina into the spinal canal and skeletal metastases

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would all favor the diagnosis of neuroblastoma.

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Age is really critical, though, when

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you're forming a differential diagnosis

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for a renal mass in a young child.

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Because in a young child, remember, those of

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you that are taking boards, that are residents,

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that are fellows, that are internists, that

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are pediatricians, that are new to MRI,

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Wilm's tumor is the most likely diagnosis.

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And renal vein invasion, which we don't have

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here, is highly suggestive of Wilm's tumor.

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Let's move on with our basic introduction to

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pediatric renal masses, in this case, arising

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from the kidney, which is a Wilm's tumor.