Renal Mass Pitfalls Case Studies - HD

Introduction

Hello, I'm professor John McGahn.

I'm from the University of California Davis, which is located in Sacramento, California.

I am the director of abdominal imaging.

As such, I do both ultrasound, CT and MRI.

What I'm gonna talk to you about is some of the pitfalls that may be encountered focusing mainly on renal ultrasound but also as we do renal ultrasound and CT together.

Talk about some of the pitfalls in renal CT as well.

I hope you enjoy my presentation.

Renal Mass Pitfalls

I'm gonna talk to you about renal mass pitfalls.

I'm gonna take you through a number of different case studies today.

An alternate title could be some of the good, some of the bad, and perhaps some of the ugly of renal mass evaluation.

I'm gonna start out with fairly simple cases and then we'll progress from there.

What I'm gonna talk about is really ultrasound and ct.

I'm not gonna talk about plain films. MRI.

We'll touch base on renal biopsy too.

As we go through this, I'm gonna show you different cases.

I'm gonna give you different choices.

You don't have a response here, but you can sort of think in your own mind, would it be this, would it be that, et cetera.

Case One and Case Two

So case one and case two.

So this is case one male with a CT prior and an ultrasound.

This is a 45-year-old male with scrotal pain.

They came in with this ultrasound.

In these two case, I'm gonna give you a few simple choices.

Is this case a case of RCC?

Is it an artifact and is this case a case of RCC or is it an artifact or are they both artifacts or are they both RCCS with, if we look at this, the ultrasound was performed after the CT and with all the modern PAC systems, sometimes cts or even other ultrasounds don't always pop up on our server or come up and all this case shows us is it is important for us to go back and compare the ultrasound that shows a renal mass that was missed with the prior CT that we can see here the solid renal mass here.

Always check for comparison studies.

Remember that especially in obese patients, solid renal masses can be often missed.

Always use color flow when we're looking at the kidneys as well to see if the masses that we do identify which may be hypo coic, are they really solid masses?

Are they in fact some sort of cyst?

Here's the other case in this to me almost looked like it was a mass though it's in the classic location for aary hump.

We looked here again and it was more prominent than we normal see, and as you know this is aary hump.

So this is just a normal compression of the renal parenchyma in the left kidney and it's been compared to a camel hump but an elephant hump I actually think maybe looks more like that.

But in any case, this is a normal finding or a normal pitfall.

Case Three and Case Four

I have two cases here, case three very nicely.

They did color flow here in this case, case four, they looked at this and you look here, they compare the mass with the rest of the retroperitoneal fat.

In this case there's certain blind spots within the kidney and I've always found one blind spot in particular that we'll talk about.

So if we look at the upper pole of the kidney, remember the original image I showed you, they looked at this portion of the kidney, they didn't really look at the upper pole but they did measure the upper pole.

Upper pole of the left kidney is very difficult to evaluate.

I think that can be an ultrasound blind spot.

I do a lot of radio frequency ablation and upper pole of the left kidney is a difficult area to not only biopsy but to perform a radio frequency ablation.

If we look here, a follow-up CT, which was done shortly thereafter demonstrates a renal cell carcinoma.

So as you noted, the left kidney was fairly long as compared to the right kidney on the ultrasound study, but they missed the solid mass.

A followup exam very carefully done, demonstrated this solid mass that was actually there on the original scan but was missed and you can see it here on follow up.

So watch out for that upper pole of the left kidney.

And again, when you're doing color flow, make sure you interrogate the entire kidney.

Don't cut off a portion of that kidney.

Cystic or Solid Masses

Now is this cystic or solid?

Let's take a look at what happened here.

This is called a hemorrhagic cyst on ct.

Somebody obtained a ultrasound.

This is the ultrasound image right here and you can see this hypo coic region.

They said that this was a complex cyst on ultrasound but they did recommend a four to six month follow up.

So a follow up was obtained, I'll show you that.

But if you look here when this image was compared to the rest of the renal parenchyma, it looked like in retrospect there were echoes within that.

So was that in fact a complex cyst or is that a solid mass follow up?

Same mistake made but somebody was astute enough when they looked at this to put color flow.

So this is more than a complex cyst here.

Remember always to include that color flow.

The other key feature here, when you're looking at a phytic renal mass, try to compare it to the rest of the renal parenchyma and do not compare it to the very echogenic fat 'cause you can make anything look hypo coic.

This was a solid renal mass that turned out to be A RCC.

Pitfalls in Renal CT

I'm gonna talk a little bit about ct.

Can't go through all the different pitfalls with ct but we do a lot of scans for BCT only.

We do 'em in the ER because they think for patient throughput they wanna look for renal stones.

It's very good for renal stones.

However, in the original studies, only about a third of the patients on non-contrast CT for pain in fact did have renal stones.

Now I suspect that rate is even lower.

So maybe a quarter of patients on non-contrast CT with some sort of belly pain have stone disease

Look here Now non-contrast CT are done for anything from pelvic disease to appendicitis to diverticular disease, renal disease, et cetera.

And a lot of times it's just to improve throughput on these patients.

They don't maybe want to get a SEN creatinine, they have throughput problems so they go ahead and all order a non-contrast ct.

Even for renal disease there's lots of problems.

So if you look at this, all these different etiologies in terms of renal pathology could be missed on the non-contrast ct.

Certainly transitional cells unless there's hydro nephrosis, pilo could be missed.

Small rccs, renal vein thrombosis, infarct, renal artery aneurysms with the calcification probably would be detected although theoretically may be missed.

Non-Contrast CT Case Example

24-year-old right flank pain.

So take a look here, compare it to the left kidney.

This non-contrast CT did not show any focal abnormalities within the kidney.

So you could see what is it?

Is this renal mass and infarc pi hydro or I really can't tell, probably answer E is the correct.

So we did this, had her come back and you can see all of a sudden there's something over here in that right kidney.

We look again and we see this, there's some mass here.

We did a follow up in three weeks after treated on antibiotics and this was just focal pilo.

The point being that for flank pain, non-contrast CT in these cases may in fact be useless.

So you have to have contrast.

I put in something in there so the clinician knows that there are limits for these patients.

If we do not have contrast so solid organs, we can't exclude solid masses et cetera.

So somehow the clinicians know that in fact there are limits to a non-contrast ct.

Focal Pyelonephritis

Now certainly ultrasound can pick up focal pilo, not all the time, but here's a case where you see a very echogenic region here on the non-color flow and you can see the same area which is not perfused on the color ultrasound.

This is an area of focal pyelonephritis.

When we look at this pyelonephritis and ultrasound, in fact the kidney may be normal, there may be hypo coic regions or hyper coic regions.

Very poor profusion with either contrast enhanced ultrasound or with color or power doppler.

We follow this up and remember what was happening here.

Now with the two week follow up, it looks like everything returned to normal in this case.

A similar case with right flank pain and now we see another abnormality here.

Color, there isn't much color in that region.

This turned out to be a very small renal abscess, maybe focal pilo turning into a small renal abscess and here you can see it also on ct.

So we can pick up these findings.

Sometimes an ultrasound contrast CT will give us a better global picture of that.

Xanthogranulomatous Pyelonephritis Case

Here's a tricky case. So here's something in a large kidney.

This was called a potential mass.

In the lower pole there's something here, there's a twinkle artifact.

So we know must have been a stone in this case

I put these two together and this turned out to be zho.

Granuloma is pilo, that's the ultrasound image and this is what the CT showed.

So this kidney is essentially dead.

This kidney had to be resected.

Actually part of this was drained before resection but what was thought to be a mass was not a mass.

This is in fact an obstructed kidney, with a pyelonephritis and it's due to his antho.

Granuloma is pilo.

Cortical Medullary Phase Pitfalls

Now let's look at another pitfall of CT where we don't have a base and we have a cortical medullary phase only.

So this is obtained at 40, 50 seconds after contrast injection.

This is the most common phase to see the kidneys on multi detector ct.

So a patient with pain who gets contrast, actually this is the phase it is utilized, but if we're looking at the kidneys it may actually be the worst phase other than the base to actually see renal masses.

So here's two cases.

So here's case number seven, I label it and here's case eight, both looking at the right kidney in each of these cases.

So one of these is benign and one of them is not you.

So you can come here cyst scar, et cetera, et cetera.

Case seven, case eight, well we go ahead, we do a delayed image on this first case.

This turned out to be a simple renal cyst, fairly straightforward.

This other one was missed.

This was pre-op for a liver transplant. You can see here.

And then with contrast here, there wasn't a, a delayed phase did not go through there, but you can see how that region blended in with the rest of the medulla.

This was missed, this turned out to be A RCC and was only seen preoperatively on that cortical medullary phase.

So this is sort of a little bit of a dangerous phase.

So unfortunately hyperdense cortical masses and hypodense medullary masses, especially if it's papillary renal cell can sort of hide within the medulla on the cortical medullary phase.

Remember of all rccs clear cells is the predominant 75%, papillary is 10 to 15%.

Those are this rccs that do not enhance very much

so if you looked at a plot here from a article that I took, this basically would be the plot here of the cortex, the medulla very early in the cortical measure phase, this would be the papillary renal cell.

This would be the papillary renal cell, not enhancing much.

The medulla in time would be up here you can actually see the hounds field values of the medulla at 95, the tumor at a hundred, but you go and do delayed.

Now the medulla goes up to 1 92 very similar to the cortex.

So on that delayed phase you would be able to pick out very nicely that papillary renal cell.

But in that very early phase they may be overlap and may be easily missed.

So you have both these papillary subtype that don't enhance and also with the modern CT scanners you get more pseudo enhancements.

So the number of detectors is they increase the greater the amount of pseudo enhancement.

So we used to say if a mass enhances by 10 hounds field units, it's worrisome.

Now we sort of up that number to 15 or 20 HA field units.

So there is pseudo enhancement on multi detector CT scans.

Papillary Renal Cell Carcinoma Examples

Another couple examples.

So case number nine, case number 10, they do not look that much different.

You can see a difference here when you put 'em side by side.

But in day-to-day practice if you had this you say I can't really tell on either.

So are these cysts, r, ccc, normal, et cetera, et cetera.

Well the one on the left was a cyst.

The one on the right you can see is a papillary renal cell.

So it got followed for eight months, followed up at 20 months and now you can see that it grew but it didn't enhance a lot so it continued to grow.

But ultrasound would be very helpful in here as well to show color flow within that mass.

So this is a solid mass.

This turned out to be a papillary but it's a good example to show you how these do not enhance very avidly.

You can actually trace out curves here.

So this is a clear cell, this is a papillary and you can see how the papillary does not enhance either in the cortical medullary phase or in the nephro phase.

It doesn't go up very much as compared to a clear cell.

Here's a case that I looked at it and I mapped out, I did thin cuts through all this and I thought this enhanced so it was taken to biopsy.

One of my young associates said, look Dr McGahn, this is a cyst.

And I said Prove me wrong. And they made an error here.

What they did is they compared this hypo coic mass to the retroperitoneal fat, they turned down the gain to make this hypo coic mass look completely cystic, when in fact they went ahead and did a biopsy.

This turned out to be papillary renal cells.

So again, papillary renal cells can be very hypo coic.

When you're doing ultrasound, a couple articles have also come out on that in terms of contrast and enhanced ultrasound.

So you see here a earlier phase, later phase.

You don't see a lot of enhancement here in this.

So is this a papillary renal cell?

Is this some sort of hemorrhagic cyst contrast enhanced ultrasound with the different phases shows.

In fact there were echoes in there originally, but it does enhance and you can see it enhanced on the different phases and washes out.

This was a papillary, its twin comes up though almost exactly the same sort of thing and in fact it enhances a little more with the house field units going from about 50 up to 61.

And however we do contrast enhance ultrasound in this case.

And you can see this is a fairly simple cyst.

There was an enhancement, there may be a little bit of artifact along the wall here, but basically this is not a solid mass but would qualify as a Bosnia type two cyst.

Multiple Renal Masses

So we're gonna talk about the nephro graphic phase and we're gonna go on to multiple real masses.

A nephrographic phase really tends to be the star here and we're gonna talk multiple renal masses.

First one gonna talk about this.

So here's a solid renal mass, solid renal mass.

There may be a solid renal mass on the other kidney, maybe a cyst or two here or there.

So you have a differential. Are these multiple rccs?

Is this multiple abscesses AMLs of some type, some sort of unusual cyst of some type metastasis or lymphoma And I think those are the main things within the differential.

Von Hippel-Lindau Disease

This case also had multiple cysts within the pancreas.

Identify both an ultrasound and ct.

This is a case of von Hippo Lindo disease.

Von Hippo Lindo disease can have, you know, heman oblasts and the posterior fossa the spinal cord and is associated with a number of other things including pancreatic tumors such as cyst adenomas as well as pancreatic cyst and pheochromocytomas.

Tuberous Sclerosis and Angiomyolipomas

Another case here, this is a little different because if you look carefully, this tumor probably has some fat in it.

This tumor may have a little fat.

Some of these do not have fat, but 34-year-old with seizures.

So this basically almost becomes an mini.

These are cases of a ML. These are echogenic on ultrasound.

You can see here, here's the ct.

The question is some RCCS may have some increased echogenicity.

So do you need to follow these in asymptomatic people?

Sometimes you may, but it's very, very difficult in these cases in a, in a few percentage to know if in fact this is an RCC, which is hyper coic or these are AMLs.

But certainly if you have CT for comparison, you see the macroscopic fat.

So these tube sclerosis do have subependymal nodules in the CNS they develop giant cell astrocytomas, they have tubers essentially all over within the lung they get RDO myomas within the heart.

Retinal hammer, Tomas. So these are very common.

These heart lesions occur in the fetus or the newborn.

Some of these other things don't, are not seen till after birth or in younger patients.

Here's a case here just to show you, not all these AMLs as in this case do have to have macroscopic fat.

So this is a case of a 17-year-old with tubs sclerosis that did have multiple AMLs but they were not fatty AMLs.

Again, these are some of the op dependable nodules and they get sclerotic bone lesions.

Here's a case, it's very interesting mass, it did enhance.

You can see it here enhancing and it was called A RCC.

We have to be very, very careful here.

This patient was devastated with that diagnosis.

But I went back afterwards and I was asked to consult.

If you look very carefully after thin cuts, there is macroscopic fat here.

This diagnosis was not an RCC, but in fact it was macroscopic fat.

This is an A ML rccs.

Unlike HCCs do not have macroscopic fat, they have microscopic fat.

We'll look at that. So here's two cases.

So if you look at this hounds field units here, this one has fewer microscopic areas of fat than this.

So this has more microscopic fat.

Neither have macroscopic fat.

So you look at that and the one with more microscopic fat is actually RCC compared to the other one, which is A A ML.

So really if there is visible fat, can you reliably classify a lesion as an A ML?

If you have just microscopic fat, you really can't tell however there is fat in this case.

And this was not an A ML.

So you can see this case here, little bit of a pitfall.

Go through your, differential lipos sarcoma post R-F-A-A-M-L met.

And this is a case in which I did RFA and it ended up here.

You can see it initially, you can see the, the tumor, what it looked like after RFA and then six months, or a year later you can see now there is macroscopic fat in that lesion and that is a completely treated RCC in this case.

Lymphoma

Case number 13, multiple low density lesions seen in both kidneys.

Really not much else for anything else, no other adenopathy but it was clear in two months follow up.

So this is a lymphoblastic lymphoma involving the kidneys.

Here's another lymphoma, very large kidney in this case and in this other side there was sort of a, a mass here.

There was associated hydronephrosis CT showing that en large kidney on one side you can see that mass on the other side.

Very good correlation actually with the ultrasound.

This two was primary lymphoma involving the kidneys.

So renal lymphoma can be diffuse Enlargement as I showed you can be single masses, multiple MA masses often is bilateral and there may often be widespread disease.

So if you look elsewhere within the abdomen or in the chest, there may be other, nodules that you see or other masses that you identify.

Oncocytoma

One final mass here you can see the arterial phase.

Here you see the mass in the upper pole here you see the mass here.

So it enhances. It looks like it washes out a little bit.

This is the delayed and this is a oncocytoma.

So this is a benign renal tumor.

I looked at what is called segmental enhancement.

Inversion, which was thought to be the scenic of this, but in fact it's not all that helpful.

So before oncocytoma people thought central scars were helpful, inversion was helpful, but it's very, very difficult to separate this benign entity oncocytoma from any RCCS except for pap, which do not enhance very much.

So if you took this mass and this mass, this is actually an RCC, this is that oncocytoma, you looked at 'em on ct, you could not tell the difference as such.

Renal Biopsy and Guidance

Renal biopsy has been performed a lot.

If you have the upper pole, you can do a lot of different things.

I do most of these under ultrasound, but sometimes we have to do 'em under CT in the upper pole and in those you can have the ipsilateral side down.

You have to angle the gantry, you can go through the liver, you can do a number of different things, but in general we do both FNA and cores.

So cores are very, very helpful here.

And if you look at this retrieval rate is fairly high when you're doing these and it'll give you a definitive diagnosis.

It ends up from five to 25% of these renal masses at the time of RFA turned out to be benign entities.

We'll look at this called renal cyst in a patient.

Again, this is, what the CT looked like, but the pet was avidly hot so it could have been an abscess.

But this patient did have a lung mass and so they thought it may have been a met.

We went ahead. This is what it looked like.

We placed a needle into this sort of hypo coic, but solid mass.

This in fact turned out to be a poorly differentiated, cancer from the lung.

Can we guide other things? Well, certainly we do.

I did a study look at an ultrasound guided RFA compared to CT complication rate was equal.

We actually did better in terms of complete ablation with ultrasound compared to ct.

So ultrasound can be used, probably some selection bias, the ones I saw, maybe the smaller ones I selected for ultrasound.

The others we went ahead and we did ct.

So ultrasound can be used to guide a number of different things.

Conclusion

In conclusion, I'd like to reemphasize several points that I try to make.

Number one, there are ultrasound blind spots including the left upper pole of the kidney.

When we're looking at masses in the kidney, especially those that are ex compare that mass to the kidney, not to the retroperitoneal fat.

Always use color power doppler or contrast ultrasound.

If we're equivocating on a case, remember the pitfalls of a non-contrast ct.

So focal masses within the kidney we may miss.

Remember the cortical medullary phase of the CT is not a great phase for looking at masses within the renal medulla.

Remember also that some types of renal cell carcinoma, such as papillary renal cell do not enhance avidly and ultrasound guide to renal biopsy is a very, very good tool to use.

So I hope you enjoyed my presentation and I hope you've learned something.

Thank you.