Stone disease field marked by advances and shortfalls

January 11, 2019

In this interview, Margaret S. Pearle, MD, PhD, discusses the AUA’s guideline on medical management of stone disease and also touches on disposable ureteroscopes and percutaneous access.

Since the 2014 publication of the AUA’s guideline on medical management of stone disease, studies have indicated low utilization of the document. In this interview, Margaret S. Pearle, MD, PhD, discusses the guideline and also touches on disposable ureteroscopes and percutaneous access. Dr. Pearle is a professor with joint appointments in the department of urology and the Charles and Jane Pak Center for Mineral Metabolism and Clinical Research at UT Southwestern Medical Center, Dallas.

Dr. Pearle was interviewed by Urology Times Editorial Consultant Gopal H. Badlani, MD, professor of urology at Wake Forest Baptist Medical Center, Winston-Salem, NC.

 

You chaired the panel that developed the AUA guidelines on medical management of kidney stones. How well are these guidelines being followed today?

The results are somewhat disappointing, although I’m not sure we’ve really seen the full penetration of the guideline yet. One study looked at utilization of the guideline using the metric of 24-hour urine studies ordered in patients who had been diagnosed with a stone, although this came from an administrative dataset, rather than patient-level data. The numbers were pretty low-about 7% in a study that looked at patients presenting to the ED and being diagnosed with a stone for whom 24-hour urine studies were ordered within 6 months of the ED visit. When the authors looked at higher risk individuals, I think that number was only about 16%.

That is certainly lower than we would like to see. But the guideline came out in 2014, and my guess is that it takes a few more years to really see it start to change practice.

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The goal of the guideline was to try to create a document comprised of a set of guideline statements that would make the process of medical evaluation and management easy. I think clinicians look at it as a daunting task to evaluate stone patients medically. They don’t know who to evaluate, they don’t know what to evaluate, they don’t know what test to order, and then they don’t know what to do with the information they receive.

In addition, I think some urologists have concerns about prescribing medications, because the medications require careful follow-up and blood testing to monitor for side effects. But we’ve been prescribing medication in urology for decades whether it’s for BPH, erectile dysfunction, or cancer. We have to monitor those patients for side effects, with liver enzymes, complete blood count, or PSA. We are capable of monitoring patients for side effects of medications, and I think the same has to be done for medications aimed at stone prevention.

The guideline sets forth a fairly simple recipe to identify which patients should be evaluated, how we should evaluate them, how to treat them with diet and medication, and even broadly how they should be followed. For probably 95% of recurrent stone formers, these guidelines provide relatively straightforward recommendations for medical management. There are probably 5% of patients who are complex and will require more expertise and more testing, but I think the vast majority of stone patients can be well managed from this document.

Next:"I think disposable ureteroscopes have a distinct place in our armamentarium."Urology is all about technology and you’ve been on the forefront, especially in the area of ureteroscopy. What do you think about the disposable ureteroscope?

I think disposable ureteroscopes have a distinct place in our armamentarium. They have been shown to be safe, effective, and even cost-effective compared to some reusable digital ureteroscopes, although they are admittedly a little bigger and have an image quality that is inferior, although certainly acceptable for stone management.

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Processing and maintenance of flexible ureteroscopes, particularly digital flexible ureteroscopes, is labor intensive and costly, so for institutions or hospitals that do not perform large numbers of ureteroscopies and do not own a large array of scopes, it can be prohibitive to maintain these instruments. In those situations, I think a disposable flexible ureteroscope is a very useful device because it obviates the need for highly skilled workers to maintain these instruments.

In addition, having a disposable ureteroscope means that you never are without a functional ureteroscope. If your reusable scope breaks, you can always finish your case if you have a disposable ureteroscope available. There is clearly a role for them, whether it is for use in technically difficult cases that pose risk of damage to the ureteroscope, as a spare, or as a complete replacement for reusable ureteroscopes, and they will undoubtedly get even better with time.

 

How does the cost work out for disposable ureteroscopes?

Some studies have demonstrated that they can be cost-effective or at least cost neutral. It just depends on the setting in which they are used and the number of cases performed. However, I can imagine a model in which disposable scopes are cost-effective when you factor in the time and labor required to maintain the ureteroscope at your institution.

 

For years, there has been a debate on managing stones with ureteroscopy or extracorporeal shock wave lithotripsy. For a while, it looked like ureteroscopy was the way to go. Have there been second thoughts on this of late? Is ESWL making a comeback?

I don’t know that shock wave lithotripsy is making a comeback. By any number of metrics, whether it’s administrative datasets or case logs submitted to the American Board of Urology, ureteroscopy has definitely inched out shock wave lithotripsy as the most commonly performed stone procedure. Percutaneous nephrolithotomy remains under 10% and ureteroscopy is probably more like 60% versus 30% for shock wave lithotripsy. Younger urologists use ureteroscopy more than shock wave lithotripsy, and you can see how that trend has changed over time.

I think the change in utilization is because shock wave lithotripsy technology has been disappointingly stagnant, while ureteroscopy technology and technique have really advanced. We have better ureteroscopes, and we have technically gotten better at performing ureteroscopy. There are very few kidneys and stones that we are unable to access with a flexible ureteroscope and virtually no stones that we can’t fragment with a holmium laser. Access really isn’t an issue anymore.

But what we’re starting to look at now is effectiveness. With shock wave lithotripsy, we went through a period of time when it was first introduced in which the technology was used indiscriminately for all types and sizes of stones. Over time, we became more selective and started to identify patient subgroups for whom SWL was more or less effective. Now, we have refined patient selection such that we enrich the treated patient population with shock wave lithotripsy with those who are highly likely to have a successful outcome.

We now know that patients with lower pole stones greater than a centimeter should not be treated with shock wave lithotripsy. We also have certain CT parameters that we can use to identify patients who are likely to have a successful outcome.

We haven’t done that extensively yet with ureteroscopy. We are in a “lovefest” with ureteroscopy right now by which we are treating bigger and more complex stones, even partial staghorn calculi, ureteroscopically. But I think it is not a matter of “can we?” but “should we?” Are we doing patients a favor by doing so?

As we have been increasingly scrutinizing ureteroscopy outcomes using more sensitive imaging modalities like CT that detect residual fragments more accurately than KUB or ultrasound, we are finding that the stone-free rates with ureteroscopy aren’t as good as we thought. We are finding across the board with prospective and retrospective studies that ureteroscopy for stones in the kidney and ureter have about 50%-55% stone-free rates by CT, which is not that much better than shock wave lithotripsy, although we have never really subjected shock wave lithotripsy to the scrutiny of CT imaging.

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I don’t know that we are going to ever revert back to the utilization of SWL that we saw in the past, but I also don’t know that ureteroscope is the answer we are ultimately looking for. There may be a narrower group of patients who can be effectively treated ureteroscopically, and for those other patients, we may need look at other technologies like mini-PERC that possibly can achieve better stone-free rates, particularly for medium-sized stones. Standard PCNL still remains the gold standard for stones that are larger than 2 cm. But patients with 1- to 2-cm stones may comprise the subgroup for whom the treatment algorithm may need to change.

Next:"Access is the biggest barrier to performing PCNL."In my travels across the world, I’ve observed that PCNL access by urologists is much better outside the United States. In the U.S., it has not crossed the 10% mark that we’ve been talking about for years.

That is absolutely true. We have really lagged behind other countries in obtaining our own access. I think there are a number of barriers. In a lot of training programs, even endourology fellowship programs, residents or fellows did not learn percutaneous access if access was not obtained by the program director. However, it is required in our fellowships, so if mentors do not gain access themselves, then the fellows have to be exposed to interventional radiologists who can teach them how to obtain percutaneous access. As the residents and fellows learn more, hopefully they will carry that into practice with them.

Access is the biggest barrier to performing PCNL. It is what prevents practitioners from treating large stones appropriately and to force SWL and ureteroscopy treatment for stone sizes for which they are ill-suited. If we incorporated percutaneous access better into our residency and fellowship programs, those barriers would quickly fall.

There has been a surge in ultrasound-guided percutaneous access, and we in the U.S. have also been late to this trend. Now, there is a lot of interest here in learning ultrasound-guided access, which I suspect will help break down some of the barriers.

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Some argue that if you do less than 10 percutaneous procedures in a year, you will never become proficient. But as you learn to do it, you find more indications for it than you do currently. Anyone who starts doing PCNL, whether in private practice or not, if stones make up the entirety of your practice, you will find indications for the procedure if you know how to do it.

 

What are your thoughts on robotic ureteroscopy?

I like the thought of robotic ureteroscopy. I’m jealous of my partners who do robotic surgery, because when I walk into their ORs, they are comfortably sitting at the computer with their shoes off, no gown or gloves. They don’t suffer from back, neck, or wrist problems. I would be happy to be more comfortable when I operate, too, and I believe a robot can operate a ureteroscope better than my limited hands. Of course, there are some tasks that require haptic feedback, like placing an access sheath, that will require careful integration. But I believe there is a role for robotic ureteroscopy, and I look forward to seeing these platforms develop.

Next:Thoughts on the state of women in urology

 

Please give your thoughts on the state of women in urology.

I am very proud to have served in leadership roles within urology and endourology, and I do see a trend in which women are assuming more and more leadership roles. A recent study in Urology Practice indicated that 10% of leadership positions in urologic/subspecialty societies are occupied by women (Urol Pract 2018; 5:228-32). Ten percent is fairly consistent with the percentage of women in urology, so although women overall are underrepresented in urology, they may be appropriately proportionately in leadership roles at this time.

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However, the hope is that both of those will increase with time as more and more women enter into urology. Among younger women, we are seeing greater numbers in urology, and hopefully we will see that reflected in leadership roles.

Most organizations are making efforts to include women on their boards and in their leadership structure. Clearly, we have a long way to go. But as more women reach leadership positions, I suspect we will see more changes at the ground level and vice versa. I am thrilled to see that Dr. Ann Gormley has become the first woman on the AUA Board of Directors, and I hope at some point she might become our first female AUA president. That is a day I hope to be around to see.

 

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