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Dr. P here showing you an axial T2 spin echo image in

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3 00:00:05,200 --> 00:00:09,370 a 46-year-old man with swelling of the great toe.

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I don't think this case is any secret.

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Anytime you see a patient with swelling

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of the big toe, you at least have to

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think about this diagnosis of gout.

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However, when you start looking

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at the other projections, you may

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start to conjure up other diagnoses.

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Now, a couple of thoughts here.

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First, the T2 signal is intermediate and dark.

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Second, there are a fair number of

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septations in here, or folds in here.

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And third, there's a fair amount

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of heterogeneity in the signal.

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Lastly, when you look at the erosions

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that are created by this lesion, like

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this one right here, they're eccentric

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to the actual joint space.

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They're off to the side and there's a

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little bit of an overhanging edge to it.

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So that does favor the diagnosis of gout and

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there are multiple other erosions present.

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The lesion is quite large and it appears

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a bit more scary in the axial projection.

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So let's turn our attention to the axial

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projection and see how fast we can bring

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them down, and pretty quickly we can.

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And here they are.

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Here's a T1-weighted image.

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Here's a T2-weighted image.

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And there is the contrast-enhanced image.

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That is very heterogeneous contrast

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enhancement, which is a little bit scary.

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But when you think about how large the lesion

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is, and how little bone destruction there is,

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that further supports the diagnosis of gout.

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Now one diagnosis that can mimic a

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giant gouty tophus is synovial sarcoma.

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And there is one of those as an example

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that we delve into some detail in

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this set of educational materials.

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And you'll be able to see the similarity.

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However, the synovial sarcoma

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doesn't really like the big toe.

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While it does like the foot,

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it just goes wherever it wants to go.

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It also tends to go through compartments.

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So it'll blast right through the intermetatarsal

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space and come out the volar or plantar side.

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Gout tends not to do that.

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Second, gout has more of a

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propensity to erode bone.

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And that's surprising, you know, you think

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synovial sarcoma, it's a sarcoma, it's malignant,

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why doesn't it just blast through the bone?

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For whatever reason, it doesn't do that.

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Nor does gout, but gout erodes the bone.

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And synovial sarcoma tends not to erode the

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bone, despite an even bigger size than this.

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And then the heterogeneous

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enhancement is a little bit scary.

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That's not dissimilar

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in enhancement pattern to what

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you'll see with synovial sarcoma.

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So the diagnosis of gout here is

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certain. It's isolated to the big toe.

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Look at that erosion with the overhanging edge.

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That's absolutely fantastic.

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Let's look at the sagittal projection just

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for giggles and you can see the erosion.

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Wow.

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Look at that.

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There aren't very many malignant

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lesions that'll do that.

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Give you this very etched, well-defined, advancing

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edge with a sclerotic, well-defined border.

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That speaks to a slower-growing lesion

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and favors the diagnosis of gout.

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Now you can get gout from

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excessive purine synthesis.

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This can occur with glycogen storage disease

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type 1, like G6P deficiency, Lesch-Nyhan syndrome.

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Then you can get it with hematologic

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disorders, especially with heavy doses of

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hemolysis or myeloproliferative syndromes.

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You can get it with endocrinopathies,

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hypothyroidism, hypoparathyroidism,

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hyperparathyroidism.

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Then you get into the vascular categories,

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hypertension and myocardial infarction.

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A lot of those patients are on diuretics.

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We'll talk about drugs in a minute.

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You can also get it with renal

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disease, glomerulonephritis.

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or pyelonephritis, and then the ones we all

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know, obesity with excessive consumption

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of meat and alcohol, starvation can do it,

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psoriasis can do it, and idiopathic

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hypercalcemia can do it, and then there's

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the drug category which is quite important.

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The diuretics are known to do this.

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So this is the diagnosis of gout which

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can easily masquerade as a malignant

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neoplasm when you have a giant tophus.

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Dr. P out.