Renal Mass Evaluation and Pitfalls - HD

Introduction

I'm Dr. John McGann. I'm from the University of California Davis. I'm located in Sacramento, California.

Today I'm gonna talk to you about ultrasound and renal mass evaluation. Show you some pitfalls in evaluation of renal masses. This could be titled the good, the Bad and some of the ugly or some of the pitfalls we may encounter for renal mass evaluation.

The main thing I'm gonna concentrate on today is looking at ultrasound but also talking a little bit about CT and biopsy. I'm not gonna concentrate on plain films or MRI. I'm gonna show you different things in terms of different cases. Sometimes I'll pair cases, other times I'll just show a single case at a time.

Case Examples: Identifying Masses vs. Artifacts

So I have two different cases here, a male with a CT and a ultrasound on the left side is labeled as one and another male on the right side with scrotal pain and this ultrasound.

So if I were to ask you which of these is a mass, which of them is it a mass you could go, is it an RCC? Is it an artifact on either side? Going back to those, is there a mass on the left side or is there an artifact? And on the right side, is that a renal cell carcinoma or is that an artifact?

When we go back through this one, it's very interesting. This was presented to me by the ultrasound technologist or the sonographer who said the kidneys are normal. However, on our PAC system, I went up and I pulled up on our PAC system and noticed there was a mass seen here and you can see here where the mass is. So it's very important when performing ultrasound always to compare to prior studies.

This is a second case that is obvious when you know it, but I struggled back and forth. So we do have sometimes artifacts that look like they are masses. This is one that I knew where an artifact occurred in the left kidney and I thought this was an artifact though I struggled with it. I looked back and forth and because of this I went ahead and decided to go and eventually do a ct 'cause I struggled with this.

This is a so-called tary hump. So I'm told there's either single humped or two hump camels. So perhaps a better name for this would be a elephant hump. So there would be no confusion. But this is a normal finding. This is a potential pitfall that most people know about which usually occurs in the left kidney.

There are other normal variants such as the parenchymal. Junctional defect is where the vessels insert usually upper pole right kidney is where this is seen most commonly. Certainly the renal pyramids in kidneys may appear very hypo coic and as the kidneys forms you can have either scars or fetal loation. So these loation do occur within kidneys or you may have scars. These are all normal variations.

Case: 62-Year-Old Male with Renal Failure

Next I'd like to show you this 62-year-old male with renal failure. So here's a non-color on the left side and a color ultrasound on the right side. One thing that has been left out here, and we'll talk about this, this is of the left kidney. One thing that was done, we looked at the renal vein and if you go ahead with ultrasound you can do a great job of looking at the renal vein with a hundred percent sensitivity. This is a publication we had many years ago, but there are blind spots also within the kidney. One of them is in the left upper pole.

So a year later they did another ultrasound through this and they included a different view. They included a view through the spleen and there was a renal mass which turned out to be an RCC. This is with color through that area. And in retrospect, if you went back and you looked at that, they didn't include color here. But in retrospect you can see this very slow growing tumor in retrospect.

So try to look at the entire kidney may be very difficult. Left upper pole of the kidney is a pitfall, a very difficult area to look at. So if you look at the right upper pole, very easy to see. Left upper pole is very difficult.

Pitfalls with CT and MRI

CT is very sensitive for lesion detection, not always for characterization unless you go ahead and do a multi-phase CT of the kidneys and look for contrast enhancement or not. The same with MRI. Fairly accurate in staging however, there are pitfalls with ct. One of the pitfalls we may have no base ct. And what do I mean by that? When we do a scan for trauma or we do a scan for pain, we often just do a single phase ct.

This is such a case in which there was a mass seen here on this single phase. CT house field units measure 92. So what are we gonna do about that? What are our options? Well we can ignore, we call it too small to characterize or TSTC or there may be other medical problems in which we really just don't want to concentrate on this and there are other things to go ahead or you could obtain a bay CT to see if it's a hemorrhagic cyst. Check old studies obtain an MRI or in this case they did an ultrasound three years previously. And here is this, this was a cyst and there have been no change in size over this three year duration.

So it's very important again to not only do things prospectively look at 'em but retrospectively look at 'em.

Here's another case, very similar in which there is no bay ct. You see a mass here, it almost looks solid but this was called a hemorrhagic cyst. So they decided they'd go ahead and do a follow-up ultrasound on follow-up ultrasound. A pitfall they made is when you look at the scan on the left, they compared it to the rest of the perren fat. If you do that you can alter things in such a way they can make even a solid mass look. Very, very hypo coic.

Here they made a mistake and if you look here that and that they don't look too much different in terms of the EQU architecture, so the mass compared, but they still called it a complex this. However, the good thing they did, they followed up in four months and if you look here again, it maybe looks like a cyst but our sonographer, I ask her to put color flow on there and this is a solid mass and you can see here when you go and you look at it more carefully, here's the mass, it is not a hypo coic or even a cystic structure. It is a very solid structure here, has the same echo texture as the rest of the kidney.

Now even with ct you may come back and do ultrasound or in the future color doppler, ultrasound or contrast enhance ultrasound even better. So here's a CT in which I'm base, the hounds field units were 49. On contrast it enhanced a little bit sort of in that intermediate zone. So with these cases from the literature contrast enhanced ultrasound, this is with sono view can easily depict, there may be a few echoes in here but there is no enhancement at all within this mass. And this was cyst contrast to this other case during the arterial and delayed phase, you know the hounds field units were about equal here in the range of 60.

So again, contrast enhance ultrasound can be helpful in these cases in which we're uncertain. Remembering there are different types of renal cell carcinoma. The most common type is the clear cell type and the chromophobe type enhances exactly the same as the clear cell are very closely. But papillary renal cells do not enhance very avidly. And in fact from this publication you can see how clear cell RCC enhances very a avidly but if you overhear to a papillary renal cell, they do not enhance very much at all.

So you could see if you had a CT or it may be confusing, but if we do contrast enhance ultrasound, we do see that why the kidney enhances this mass also enhances. And this is a case of papillary renal cell carcinoma. This case also illustrates utility of ultrasound. So if you look at this, if you took hounds field units of the entire mass here, hounds field units only increased from 16 to 20 to 24. But there's two pitfalls in this case. Look at the entire lesion and use ultrasound.

So when we looked at the entire lesion and we did different uh window settings, you see here lower uh CT numbers, lower hounds field units centrally. But the hounds field units on this contrast at the periphery we 54 there is we did color flow as well but you can see this is a very necrotic papillary renal cell in which there is solid components around the periphery of the mass ultrasound was extremely helpful in this case.

Ultrasound Evaluation of Small Masses

Now what about ultrasound? A lot of times it's used to look at masses are they cystic or solid? But a lot of very small masses may be missed with ultrasound. So what I decided to do is we would look at path proven cases of RCC. We had 91 cases of path proven RCC in which we had ultrasound. Many of these were cases in which I performed cryoablation or RF ablation of the kidney. So I did many of these ultrasounds of the kidneys.

We then analyzed these based upon a five point scale from echogenic. Being very echogenic is renal sinus fat to very hypo coic. And when we looked at this we graded five as very echogenic, as echogenic as renal sinus fat. As we can see these should be equaled to those that are very hypo coic almost looking cyst length to those that are iso coic with the renal parenchyma.

A couple different things we found when we go ahead and split those into those uh R or masses that are larger than two centimeters or less than two centimeters of the rccs. We had a huge propensity of seen lesions that were very hyper coic, less than five, less than two centimeters. And in fact this was statistically significant at p equals zero zero uh, one value. So it was interesting to see why we had that.

Here's a couple of cases. So these very echogenic masses even at two centimeters such as this we pick up and these can be rccs. Remember the overall incidence of RCC and the very eco being very echogenic and our overall group was about 10% Overall smaller though when we looked at the smaller group it was very high closer than 25 to 30%.

The same thing here. Very high coic lesions we're seeing more commonly in the group under uh two centimeters this group as compared to those over two centimeters. So that was significant at this P value.

Here's such a case. So here's a case in which there is a renal lesion. I had looked at it on CT then I recommended biopsy. One of the people that biopsy it said well no, no I think it's just a cyst. So I told him, prove to me that it is a cyst 'cause it looks like on CT it isn't. So the mistake made here again they compared this lesion to the rest of the retroperitoneal fat. Instead of comparing it to the kidney, they went ahead did a biopsy. This ended up to be a papillary renal cells.

So some of these renal cells can be very hypo coic. You need to look at color flow, you need to compare 'em to the rest of the renal parenchyma.

Now the most interesting group are those that are ISO coic and my theory is this, when you have an ISO coic lesion, it's very small, less than two centimeters. You're not gonna pick it up. But if you go ahead and you have a bigger and bigger lesion, you're gonna see it eventually. So if there're iso coic masses, we may not identify them on ultrasound. These would be missed cases. So I am sure there are other lesions less than two centimeters that we would not pick up.

Let's look at an example of this. So this is a transfer scan through the inferior pole of the kidney. The right side we see this mass. Then this is a longitudinal scan of the more superior pole. We see this cyst and we saw other cysts but there's something here that was missed. We followed up in one year. Again this mass started to grow. You can see it color so it is a solid mass but we looked at the cyst again but there's something on this scan that we missed as well.

So in retrospect, when you went back after we did a CT on this patient, you can see this was the RCC. This was an oncocytoma, that lesion that was hypo coic with color flow. But this corresponded to the RCC missed in 2011, missed again in 2012. But in retrospect you see the bulge here. You see there is a little bit of a contour deformity but I think many of these very small rccs that are are ISO coic to parenchyma we do not detect.

Laundry List of Renal Masses in Adults

Now I'm gonna go through a laundry list of different renal masses in the adult. We're gonna start with this. This is a ML. Again they're very echogenic. Sometimes I think they're more echogenic and if they're very small, less than one centimeter, most people will ignore these. If they're larger masses, sometimes they may be difficult to separate from RCC.

So this is A A ML. This is another A ML, this is with CT and there is fat in that lesion. So that's macroscopic fat consistent with an A ML. This is an unusual A ML but when you see an A ML sort of is compressed a little bit like in this case it is not completely rounded. This indicates this is more likely a benign rather than a malignant lesion. This indicates this is a soft rather than a hard mass angio.

Myel lips if they get to be greater than four centimeters may bleed. Therefore a lot of people go ahead and would embolize these masses. They're often associated with another entity such as in this case where the CT shows multiple renal masses, some of which contain fat within them multiple AMLs. And this is a case of tuberous sclerosis. So these tubers occur within the kidneys as AMLs. They're often associated with cyst. They have giant cell astrocytomas that can develop within the CNS system. They have rhabdo myomas when they're born within the heart and lamb within the lungs. So there's lots of different things that occur here, but one of 'em are these AMLs within the kidney.

Focal Pyelonephritis

Alright, here's another case, looks a little echogenic here, 26-year-old female. But if you look at this, it may be a little more wedge shape than most. So a longitudinal or sagittal scan, a transverse scan with color, it's a hypovascular area here and you go down your laundry list and this turns out to be focal lon nephritis. So within two weeks you look at the same kidney, you can go back here, see it, you see the mass. Two weeks later it's gone.

QPI may not be seen, it may in involve the entire kidney. You may have a hypo coic or a hyper coic area and it may be a vascular area, a vascular area as well.

Renal Abscess

Here's another case in which there's a renal abscess. So by this time it's more hypo coic. It is liquified here. So this is the kidney without color flow. You can see the mass here with color flow. So it ends up that renal abscesses are more hypo coic and appearance. This is the corresponding CT and uh, these can be treated usually if they're very small with antibiotics rather than being aspirated or drained.

Xanthogranulomatous Pyelonephritis

Here's a very complex case. So this is a longitudinal ultrasound through the left kidney and you see centrally there's something here that has ring down so you know that is a stone but look at this other mass and the appearance of the kidney, it almost is, is this is the cortex, this is hypo coic, hypo coic. So what is this? Well I'm all on the line of infection and this is antho. Granuloma is pyelonephritis.

So it's sort of a chronic infections caused by stone disease, maybe either focal or it may be more complex in that involved the entire kidney. We ended up putting a drain into this case and then it ended up on this case that required a nephrectomy usually in middle aged women, uh, infecting organisms or e coli proteus. And you end up having this chronic infection that literally can destroy the entire kidney. You get hydronephrosis but in addition you get destruction of the parenchyma and it may be segmental or it may be complete.

Renal Lymphoma

Alright, let's go on to another case. So ultrasound here, corresponding MRI sort of more or less a ill defined almost ISO coic mass. We're going to ignore the hydronephrosis but you can see the same thing here over a more T two weighted MRI. You look here we could do a three month follow up. This turned out to be renal lymphoma. So renal lymphoma can appears diffuse enlargement or subtle mass as in this case.

Here's another case of lymphoma. So this involved the right kidney, you can see how much enlarged this kidney is corresponding MRI and ct. So this is diffuse involvement of the kidney by lymphoma.

Here's another case of lymphoma, multiple hypo or hypodense masses seen on ct. You can identify these throughout both kidneys. So this presented as multiple masses. This is the two month follow up. So lymphoma can have multiple different appearances. You can get renal enlargement, you can get renal masses, they can be multiple or they can be single or they can sort of blend in between as I showed you on that other you can have hematogenous spread or if you get lymphoma of the nodal mass around the aorta it can be directly into the aorta. Usually a bilateral process.

Cystic Renal Disease and Bosniak Classification

Let's finally talk about some cystic disease. So I'm not gonna labor on the point of polycystic uh, renal disease but I'll talk to you about Bosnia axis very quickly. So when you have Bosnia axis you can have a classification of uh, bosniac two. Now this classification is really with ct so been a lot of talk about having a bosniac classification for ultrasound for sort of these ultrasound equivalents where we would may wanna get follow up. And then there's also a talk of having a Bosnia classification for contrast enhanced ultrasound. So it may be more sensitive ultrasound may be than CT and picking up lesions.

So these Bosnia two may be very high, you know, thin line hairline, septations, cystic lesions, fine calcifications, you know not much else at all. So if they're complex this or two cysts together, they may be, you know, where you would say well there's a little bit something here I'm worried about or there may be a little wall thickening or calcifications. You might want to go ahead and and follow these up. These are called bosniac two F.

These are different examples. An ultrasound of bosniac two lesions, some of these some people would follow. So here's sort of a cyst within a cyst. Another very similar case with that septations with color flow. Simple septations, something like this you may not follow something where you get a little bit more color within it or the septation may be a little thicker. You may follow these up in a year.

Finally category three are sort of indeterminate masses. Usually these are removed. If we see these there can be very cystic rccs which are very complex and very difficult to diagnose. So this is the same case, this is a different portions of the kidney. But you see this cyst with rather thick walls would have the same appearance on ultrasound thick walls and just imagine it has color flow within it. So this would be more or less a bosniac three case. You would end up resecting that lesion that was resected, it was the cystic clear cell RCC then BOS four really if you think about it, rccs with necrosis.

So there may be cystic areas in there but the main thing is there a solid mass. So if you look here, so and a lesion such as this, you can see it's mainly a solid mass, an ultrasound with some increased color flow but with cystic components. Here's the corresponding mr. I went ahead and I did a biopsy of this then we did RFA to ablate this uh, cystic clear cell.

Now here's another one that could be mistaken for a cystic clear cell. Very young male multiple septations in this mass. Well localized mass, very discreet mass here in the upper pole of the left kidney. And this is was in a young male but it has a bimodal age distribution. Females greater than 40 males less and it almost has the same characteristic appearance all the time. However, because you can't tell these from cystic rccs, it is recommended that these multilocular cystic neuromas be removed.

There are cystic, you know, lesions that are hard to differentiate sometimes from RCCS or cystic rccs. Therefore they do recommend that these are removed and usually occur in this bimodal uh distribution in young males as well as 40-year-old females.

Distinguishing Benign vs. Malignant Lesions and Biopsy Utility

Now how can I tell if this lesion on the right side here is benign or malignant and is it different from this lesion? These two lesions they're in different patient. One of them is an oncocytoma, one is A RCC. You cannot tell these apart because of this we go ahead, we do biopsy and if we note that they are an RCC, we'll go ahead and we'll do RFA or other uh, treatments such as cryotherapy.

So if you look at different series have been written, it's a fairly high retrieval rate. Many people recommend cores of these which is safe to perform as well as FNAs is what we do. Many of them do 18 gauge cores instead of these thinner cores. Also a 22 gauge and the results are fairly good. Some reports such as this one showed that finding aspiration actually did a little bit better than cores, but most series now recommend cores. There is no tumor seeding that is seen with these that we used to be thought there would be. So it's safe to do these. You obviously have to have all your coagulation studies, et cetera, uh, to make sure they're in a range where you feel safe. So you do both FNA and course and finally get a fairly good retrieval rate with most of these.

Now here's a case here in which there is a mass Seems almost looks like that dormatory hump but it was fairly avascular. This patient had metastatic disease, a needle was placed into there, then a core biopsy was performed. It ended up that this was a poorly differentiated lung cancer to the kidney.

So I've gone through this different laundry list. We've gone over different types of rccs. We looked at focal pilo abscesses, talked briefly about oncocytoma. Have a very similar appearance most of the time as rccs AMLs are very echogenic talked about different types of uh, cyst and talked about mets a little bit lymphoma and then some of the pitfalls that may be encountered.

Summary

So in summary, we first have to be familiar with anatomical variants. So there are different anatomical variants in the kidney. I would always recommend use the color flow for renal masses, especially hypo coic masses and turn up your sensitivity in such a way that you could see color flow. 'cause many times these kidneys are very deep and it's hard to identify color flow, watch for blind spots in the kidney. Apropos of the left kidney is a blind spot that you need to uh, realize.

Use color flow for the renal vein. It's exquisite tool full doing that. And you can see the renal vein almost a hundred percent of the time with color flow. Uh, not all echogenic masses are a ML so just be cognizant of that. If they're very small, probably don't need to follow 'em up. If they're larger in the ranges of two centimeters, you just have to rely on how echogenic they are. If you go ahead and do further therapy or you go ahead and do a CT or mr or do you feel safe to watch them and wait six months or a year, remember that there are probably a number and in fact most of our ccs are iso coic, renal parenchyma.

As they get larger they deform the capsule, but when they're smaller they may be very difficult to see. Some rccs are complex and cystic and I went over these bosnia classifications, but there are also may be other cystic rccs. So you have to look for any solid elements, thick septus, anything that look worrisome to you. And there's a broad differential that I've shown you from lymphoma to mets to abscesses to RCC for renal masses and for a number of these, uh, renal biopsy is very, very safe. So always think of renal biopsy if you have a question.

So I'd like to thank you for your, uh, time. I hope you enjoy this presentation. And just a summary of looking at, uh, different renal masses and some of the pitfalls we may encounter. Thank you very much.