Podcast: Using Shock Waves to Treat Kidney Stones
Kidney stones affect 1 in 500 Americans each year. Kidney stones form when urine is concentrated and minerals crystallize and stick together to form small, hard deposits. These deposits can affect the urinary tract from the kidney to the bladder. Most can be painful as they pass but do so without causing damage. Shockwave lithotripsy is a non-invasive way to treat a single kidney stone.
Shaun E Wason, MD, discusses Shock Wave Lithotripsy, a unique treatment for kidney stones.
Shaun E. L. Wason, MD
Shaun E. L. Wason, MD, FACS is an Assistant Professor of Urology at the Boston University School of Medicine. He specializes in minimally invasive urologic surgery using robotic, laparoscopic, percutaneous and endoscopic techniques to treat a wide variety of urologic disorders. Dr. Wason completed his residency training in Urology at Dartmouth-Hitchcock Medical Center and his fellowship in endourology, laparoscopy and robotic surgery at Eastern Virginia Medical School (EVMS). He was an Assistant Professor of Urology at EVMS prior to joining the faculty at BUMC/BMC. His clinical research interests include radiation reduction in the operating room, surgical simulation and the application of 3D printing for surgical training. Dr. Wason is board-certified by the American Board of Urology and is a Fellow of the Endourological Society and American College of Surgeons. He is also a member of the American Urological Association.
Melanie Cole (Host): Kidney stones affect about one in 500 Americans each year. For many, they will pass on their own. However, for some that don't, a unique treatment is available. My guest today is Dr. Shaun Wason. He's a urologist at Boston Medical Center. Dr. Wason, explain for the listeners, what are kidney stones?
Dr. Shaun Wason, MD (Guest): Absolutely, thanks for inviting me. So kidney stones form when your urine contains more crystal-forming substances such as calcium and uric acid than the fluid in your urine can dilute. They typically form in the kidney and most kidney stones will pass spontaneously without any surgical intervention.
Melanie: Are there certain times of the year when they're more common?
Dr. Wason: Well the general thinking is that kidney stones form in the summer when folks are dehydrated, but we're currently investigating the role of temperature on the formation of kidney stones, and that may not be the entire situation. So we see patients that present with kidney stones throughout the entire year.
Melanie: Who's at risk for kidney stones? And what are the symptoms that someone would notice?
Dr. Wason: Patients that are chronically dehydrated, patients that may not have free access to water. Certain professions that are around heat such as cooks. Other patients that have chronic dehydration such as those with what we call an ileal conduit or typically loose fluid are more prone to kidney stones. Also patients that are obese and diabetic have also been shown to produce quite a bit of kidney stones.
Melanie: So are there something people would notice? I mean is there pain? Is there something that would notice that would send them to a urologist?
Dr. Wason: Absolutely. So pain is the number one presenting symptoms of patients that have kidney stones. Usually the pain starts in the abdomen and radiates to the flank. As the kidney stone passes, the pain can progress down towards the groin. So some patients not only will have pain, but they'll have nausea and vomiting, and then this is usually cyclical. Patients may also report some blood in the urine. If there's a super imposed infection with the kidney stones, these patients may have subjective fever and chills and shakes.
Melanie: So what is the first line of defense? As I said in my intro, and then you said again, some pass on their own spontaneously. For the ones that don't? And how long do you wait to find out if they're not going to if it's causing pain? So explain a little bit about what happens once one is diagnosed.
Dr. Wason: So usually patients present quickly to the emergency room, they're evaluated with what we call a CT scan, or a CAT scan of the abdomen and pelvis, and this will outline the location of the stone and the size of the stone. Stones that are small will tend to pass spontaneously, especially if they're in the distal part of the ureter. Larger stones that are up towards the kidney may not pass spontaneously. If there's no sign of infection, then we usually give the patient the trial of oral therapy such as that what we call an alpha blocker, which we think helps to relax the ureter. We tell them to remain hydrated, and then we just give them time.
For patients that cannot tolerate oral therapy or water, and they're just too nauseous or they have persistent pain, then those are the patients that we would consider more treatment, and there are several different treatment options out there.
Melanie: So speak about some of them.
Dr. Wason: Okay. So in the acute situation, if there's an infection, then we want to drain the kidney and drain as much bacteria as possible, so we'll put in a ureteral stent which is a small little rubber tube to drain the kidney. This can also be placed directly into the kidney through the back. If a patient doesn't have any signs or symptoms of infection, we can offer them what we call ureteroscopy or shock wave lithotripsy.
Ureteroscopy involves taking a small little camera and a telescope and putting it through the bladder into the ureter up to the level of the stone. Once we see the stone under direct vision, then the stone can be fragmented into a lot of little pieces which could then be extracted at the time of surgery. This is invasive and it does require placement of a ureteral stent at the conclusion of the procedure.
In other situations where a stone may be located in the kidney or the proximal ureter, we can offer them what we call shock wave lithotripsy, or ESWL for short. And what this involves is targeting the stone using either fluoroscopy or ultrasound and sending shock waves through the body, so through the skin, the tissues, and the fluid surrounding the stone, which then break up the stone into smaller little pieces that can then be passed spontaneously.
Melanie: Wow. So how cool is that? So tell us a little bit about the advantages and possible disadvantages of using that shock wave lithotripsy, and can it only be used if there's one stone? What if there's more than one?
Dr. Wason: Great question. So shock wave lithotripsy has been around since 1980 when the first shock wave lithotripter came on the market. Interestingly, this was used to test aircraft equipment that was undergoing supersonic flight, and then it quickly became the standard of care for the treatment of kidney and ureteral stones for the subsequent ten years. We use shock wave lithotripsy mainly for a solitary stone, although it can be used if there's maybe another kidney stone and you have successful fragmentation of the first stone. So we typically will reserve this for a solitary stone. Stones that are in the kidney or in the proximal ureter or in the distal ureter tend to be targeted fairly easily.
It's an outpatient procedure which typically takes about forty-five minutes to an hour, it's truly non-invasive in that there are no surgical cuts or no instruments going inside the body. The patient is under sedation and then we have a technician that's with us to help us target the stone, and then we send shock waves, approximately 2,500 shock waves through the body to fragment the stone. Once the stone is completely fragmented, then the procedure is stopped.
Melanie: What happens to the little fragments?
Dr. Wason: So the patient passes those spontaneously. We encourage them to remain really hydrated after the procedure, and the fragments are usually about one millimeter or less in diameter and most patients don't even feel the stones passing. We do send them home with a strainer to strain their urine to collect the stones, which we ask them to bring in for analysis after the procedure is complete.
Most of the stones pass within about two weeks after the initial procedure, and we have them follow up in the office for an ultrasound and an x-ray at that two-week mark to ensure that we've had excellent fragmentation of the stone.
Melanie: If someone has had one, are they then at risk for another?
Dr. Wason: Absolutely, unfortunately. Most patients that have had one stone in their life have about a 50% chance of having a current stone in their lifetime.
Melanie: Wow. So is there a way, Doctor, that they can be prevented?
Dr. Wason: It can. The number one recommendation that we give to all our patients is to increase the water intake. We like to have their urine output about two or two and a half liters a day. So the urine has to be very clear. The amount of fluid that the patient drinks can be a mixture of a variety of fluids just to keep their urine dilute.
We also offer metabolic testing where we analyze a patient's urine for a twenty-four hour period, and we look for things like the urine PH, the urine citrate, the calcium, the oxalate levels, and then we can tailor our dietary recommendations to these patients. It's very important that patients have an actually normal calcium diet. We don't want them to restrict their dietary calcium. We also want them to limit their dietary oxalate, and then we also want them to have a good amount of fruits and vegetables which have a high citrate mode, which have been shown to prevent kidney stones.
Melanie: Dr. Wason, please wrap it up for us with your best advice about kidney stones, possibly preventing them in the first place, and what you want listeners to know about shock wave lithotripsy.
Dr. Wason: Sometimes kidney stones cannot be entirely prevented once a patient has had a kidney stone attack. There are a variety of treatment options for kidney stones. First line of therapy, according to the American Urologic Association guidelines, is shock wave lithotripsy, which is a truly non-invasive way of treating stones along the entire urinary tract. It's safe, it's effective, it's an outpatient procedure, and does not require any general anesthetic. I think the number one rule for patients that have had kidney stones is to keep their urine as dilute as possible and make sure that patients eat a well-balanced diet that's high in fruits and vegetables.
Melanie: It's great information. What a fascinating procedure. Thank you so much for joining us today, Dr. Wason. This is Boston Med Talks with Boston Medical Center. For more information you can go to www.BMC.org. That's www.BMC.com. This is Melanie Cole, thanks so much for listening.