Intro: Welcome to UAB MedCast, a continuing education podcast for medical professionals, providing knowledge that is moving medicine forward. Here's Melanie Cole.

Melanie Cole, MS (Host): Welcome to UAB MedCast. I'm Melanie Cole. And today, we're highlighting and our discussion is focusing on kidney stones, a chronic disease. Joining me is Dr. Kyle Wood. He's a urologist, an Associate Professor of Urology and the Vice Chair for Urologic Research at UAB Medicine.

Dr. Wood, it's such a pleasure to have you join us today. So, why don't you tell us a little bit about kidney stone disease, how prevalent it is, and the scope of the issue that we're talking about here today.

Dr. Kyle Wood: Thank you, Melanie. Yeah. So, kidney stone disease affects about one in 10 individuals, so it is quite prevalent and it's actually been growing in prevalence over the years. If you look at large epidemiological studies and the trends, kidney stone disease keeps on increasing, and a lot of that is secondary to dietary indiscretions and medical comorbidities, which is really why it's a chronic disease state and why we have to address it as a chronic disease.

Melanie Cole, MS: Does getting kidney stones predispose a patient to kidney disease? And we're calling kidney stones a chronic disease as they can recur, but does it then lead to other kidney diseases?

Dr. Kyle Wood: So, I think the first aspect of this is, you know, what about kidney stones makes it a chronic disease? And some of that is associated with other chronic conditions. So if you look at hypertension, diabetes, cardiovascular disease, and chronic kidney disease, kidney stone disease is associated with all of those conditions. And a lot of them are bidirectional, meaning if you have kidney stones, you are more likely to develop one of those other medical comorbidities. And if you have those medical comorbidities, you're more likely to develop a kidney stone. So, that bidirectional nature shows that if we just think about stone disease and if we are seeing a patient with a stone in our clinic, it may actually lead us to finding other conditions and other chronic conditions.

And to your point, Melanie, it is very much a chronic condition. One, because if you are a stone former, you are likely to have another stone. So, it's just chronic by nature. It's not an episodic one-time event. And so, that bi-directional nature just really points to clinicians looking at individuals that come in with stones and recognizing that they can develop other conditions and, in addition, looking for those other conditions because they may actually be the cause of their kidney stones. So to answer your question, it is very much a chronic disease because of its associations.

Melanie Cole, MS: Well then, along those lines, Dr. Wood, for other providers, tell us how we should be working up our kidney stone formers, knowing what you just said.

Dr. Kyle Wood: Yeah. Just like in any other condition, it really starts with a good history and physical exam. So, there are a lot of causes for kidney stones and there are some conditions where they run in families and there are genetic components that cause kidney stones, so it becomes important to get a good history on the patient.

And some of the history though also pertains to their dietary habits and their work life. So for example, kidney stones contributing factors can be a lot of the diet that people take in. So for example, low fluid intake creates an environment where kidney stones can come in. If a person is working outside and they have a lot of loss of fluid because of, say, sweating or perspiration, that can contribute to their stone disease.

Other things in the diet that contribute to stone disease is high salt intake. Now, you can imagine the American diet is very high in salt and very high in protein, and we have a lot of processed foods and fast foods, and those can be very high in salt as well. But salt is a major contributor to kidney stones, and the mechanism for which that occurs is as we take in salt, it causes calcium to be excreted in our urine, and most kidney stones are made of calcium and thus we have an increased stone risk.

As I pointed out, high protein intake can actually contribute to stone disease as well. And the mechanism to which that happens is as we eat more protein, it causes an acid load to the kidney and it creates an environment for stones. And the American diet is very much focused on protein intake. We've almost always taken a large portion of protein with our meals and then not enough fruits and vegetables. You know, fruits and vegetables for a lot of our patients can be a huge expense. And so, a lot of our patients go without fruits and vegetables, but fruits and vegetables adds a major inhibitor to our diet, which is citrate. And so, without a balanced diet of fruits and vegetables, we can have not enough inhibitor of stone disease and actually contribute to our stone risk.

And so, that's the dietary proportion, and that can be taken out in the history. I talked about the family component and the genetic component, and I talked about the work life of our patients to determine if they're having increased risk of stone disease because of their work.

Melanie Cole, MS: Well, as we're talking about the workup, how involved are advanced practice providers in identifying and evaluating symptoms of kidney stone management? And you know, speak a little bit about that if they are involved in this.

Dr. Kyle Wood: Most providers, whether it's a, you know, advanced practice provider or an emergency room provider, or a primary care provider, it's not all Urology, right? A large portion of our patient population are going to have kidney stones and they're going to be coming in and interacting with all of these providers.

The advanced practice provider has a unique opportunity because they may be following this patient for other reasons, and then find out they have a fairly complex stone history. They've had multiple events, they've had multiple presentations to the emergency room. They might have imaging with a stone that's not causing any problems right now. And this gives us a unique opportunity to advanced practice provider, a unique opportunity to work the patient up, to go a little more in depth about what the workup is. As I stated before, it includes the history and physical exam, but it also requires a workup, and some of that is what we call a metabolic workup, and that is blood tests, so simple blood tests. What you're looking for in the blood test is, say, serum calcium. So, one condition that can cause stones is primary hyperparathyroidism. So in patients with increased levels of parathyroid hormone, that can actually increase their calcium in their blood. And so, that can be picked up on a blood test and that can actually get excreted in the urine and form kidney stones.

The other workup that we do for our stone formers is 24-hour urine analysis. It's actually a relatively simple test. And unfortunately, we don't do it enough in our stone-forming population. Even as urologists, we fail to work up the majority of our patients, even despite having guideline statements that say we should work them up. But basically, we send off a 24-hour urine sample, and these are now a single test. It's like a stone workup test, a 24-hour urine workup for stone disease. And they look at all of these parameters that cause kidney stones, so we can really personalize the care of these individuals and help them come up with both dietary and medical management for stones to prevent future episodes.

And so, again, the APP, the advanced practice provider, if they have a patient coming in and they know they have a stone history, it gives us a unique opportunity to work the patients up and then drastically change the outlook of their future. So if they're not having stone events, they're going to be extremely thankful to you as a provider.

Melanie Cole, MS: What an enlightening answer that was. Now, Dr. Wood, what's unique about UAB and how you manage kidney stones? Tell us a little bit about some of the treatment choices, some of the new and exciting tools in your toolbox.

Dr. Kyle Wood: Yeah. So, I'll start with what we have in our toolbox, which I think is limited, and I think that's really why a lot of providers haven't gone through great lengths to approach their stone formers and work them up because there's not a lot of tools to treat them.

Some of the tools, as I stated, are really dietary recommendations. And then, there's other medical therapies. So just to name a few, all of the thiazide treatments that we use for blood pressure, so hydrochlorothiazide, chlorthalidone, indapamide can all be used in stone formers to reduce their urinary calcium excretion and to prevent kidney stone disease.

And so, a lot of our patients, as I mentioned, they have that bi-directional relationship with hypertension, so we have a unique opportunity. If they have stone disease and hypertension, we could actually be treating them with a thiazide and managing both the disease states. And so, that is one therapy that can work to prevent kidney stones. And the 24-hour urine, as I mentioned before, becomes important here because you really want to ensure that they have hypercalciuria or high calcium in their urine, and that's when we would use these thiazide treatments.

Another treatment is potassium citrate. I mentioned the fruits and vegetables, having a large amount of citrate that prevents kidney stones. So, citrate's an inhibitor of kidney stones. And so in certain individuals, they may have what's called  hypocitraturia or low citrate in their urine, and we can give them a pill, potassium citrate, and prevent kidney stone disease. So, that gives us a unique opportunity to treat them with that.

So, what we specialize here, I'm an Endourology-trained, previous fellow, I went through Urology training, and then I did fellowship in Stone Disease, both the complex surgical management and the medical management of stone disease.

So, we have a few unique things at UAB. We have a multidisciplinary stone clinic, so where we take our complex stone formers and we have both nephrology and urology working those patients up to come up with the best treatment plan and personalized care plan for those individuals. For patients that seem to have a potential of a genetic component, we do genetic workup here. We have a genetic test that looks at a 45-gene panel. That is free of charge to the patient. It's a buccal swab, so it's easy. We do it in the office and we can find out if they have a genetic component to their stone disease and that can really open up a lot of opportunities for those individuals.

We have a care center here. We are one of three care centers in the United States. It is an Oxalosis and Hyperoxaluria Foundation Care Center. We have a special program through which any of our primary hyperoxaluria patients can go through. So, primary hyperoxaluria is a very rare disease that causes kidney stones. But because we have that care center, it allows us to work on all of the complex rare stone diseases that exist out there. So, we have that unique opportunity here. In the Department of Urology, we have a kidney stone service line, so all of our patients go through a unique service line. Despite being a very large institution, we've really set up a different care pathway for our stone formerS. So, they get a unique interaction with both the urologist, but also our clinical coordinators and the operating room and nephrology and other dieticians. And so, we have this unique care pathway where we take all of our stone formers through, so if they're having surgical intervention by me or if they're having medical or dietary management.

Melanie Cole, MS: Wow. Thank you for telling us also about genetic testing because that's a very interesting aspect of kidney stone disease. Now, I'd like you to just speak a little bit about anything you see happening in the future? What do you see as far as kidney disease and kidney stone disease as a chronic disease for other providers around the country? Where do you want to see research going, clinical trials? What do you want to see happen?

Dr. Kyle Wood: So, one of the unique aspects about UAB is our Kidney Stone Research Lab as well. We have phenomenal PhDs and MD PhDs working together in our Kidney Stone Research Lab to kind of understand stone disease. And that's where the research needs to go. As I stated, we really have not a lot of tools in our toolbox.

So if we're going to get at being able to treat stone disease, we actually have to understand all the different types of stone disease. And so, there are a lot of causes for kidney stones as that I alluded to. And within each of those causes, we really need to have a better understanding of the pathophysiology.

 I do think we are moving to a more personalized approach to stone disease, and that starts with the research, but that also segues into the treatment options. And so, genetic testing is one aspect of that. At UAB, we've tested over 300 individuals. But most recent analysis, we looked at a cohort of 285 individuals that we've genetically tested, and 6% of those patients have a monogenetic cause for kidney stone. So, one of the, I think, the unique opportunities in Urology and across all clinicians is recognizing those individuals that may have a genetic cause for kidney stones, and then putting a multidisciplinary approach in there, and then also really giving them personalized treatment. So, that's where I think the field's going.

I think we need to stop thinking about kidney stone disease as an episodic event that we just treat either surgically or medically. And then, we send them out and we say, "Good luck until you form another kidney stone." We really do have to think about it as a chronic disease, and then how do we treat this chronic disease and in a multidisciplinary fashion? That's where the future should be going. And that starts with the workup. It starts with genetic testing. It starts with noticing when it's an unusual scenario and that actually starts with all the clinicians out there recognizing, "Hey, we have a stone former." Yes, it's common, but this person might be in a situation if they've had multiple stones, if they had early onset of kidney stones, say as a pediatric patient. These should be red flags.

So, red flags are early onset of stone, chronic kidney disease and kidney stones, because we pointed out that they're linked. Nephrocalcinosis, so if you see on imaging, whether it's ultrasound or CT scan, that individuals have deposits of calcium in their kidney tissue, which is referred to as nephrocalcinosis, that's a trigger that something else is going on, or a highly recurrent stone former. They come in and they tell you, "Yeah, I have a jar of kidney stones at home that I passed." Or if they come in and their CT scan has really large stones bilaterally on both sides, those are all scenarios where we need to change the field. We need to work those patients up, and that's the future.

And with the studying and defining those patient populations and learning about them, that's where we'll expand our treatment options. And so, I do think the future is a more personalized treatment algorithm for all of our stone formers, but that's going to take a little while to get there. And that's really where all of the clinicians that are listening to this can serve the community.

Melanie Cole, MS: Dr. Wood, what an amazing guest you are. Thank you so much for joining us today and sharing your incredible expertise with other providers. You've given us so much to think about. Thank you again. And for more information, please visit our website at uabmedicine.org/physician. That concludes this episode of UAB MedCast. I'm Melanie Cole.