A leading authority on kidney stone disease, James E. Lingeman, MD, of Indiana University Health, updates Renal & Urology News on the state of urinary stone treatment, including a possible rebirth of extracorporeal shock wave lithotripsy and the pursuit of the “holy grail” in flexible ureteroscopy.
Extracorporeal shock-wave lithotripsy (ESWL) has been the gold standard for the treatment of urinary-tract stones, but are we moving away from that approach in favor of flexible ureteroscopy or another technique?
Dr. Lingeman: Shock wave lithotripsy is still probably the most common treatment done in the U.S. for most stones. The peculiar circumstance here is that while we always assume that technology is going to improve, that hasn’t been the case with lithotripsy. And the reason is that the companies that built these machines starting back in the 1980s didn’t really understand how they worked, so it was hard for them to improve them.
Dornier, which is a German company [www.dornier.com], built the first lithotripter, and did a brilliant job. When they tried to change it and improve it, they were unable to improve it because they didn’t understand the basic physics of how it worked. In fact, it got worse, progressively, as they tried to change things. It changed, but not for the better.
The reason we know that [the attempted improvements] were on the wrong track is that we [Dr. Lingeman and fellow researchers at Indiana University School of Medicine] have had a grant from the National Institutes of Health for about 20 years looking at the basic science of shock wave physics and how it works. And we’ve learned a lot of things that the original developers have only recently acknowledged to be correct about the way in which lithotripsy works.
Now that we’ve gained so much knowledge since the lithotripter first came into use in the early 1980s, can’t we just make our own improved version?
Dr. Lingeman: We actually are thinking about building our own lithotripter. There is one very small company in Germany [trtllc.com], headed by an engineer who started with Dornier 30 years ago. He’s attended some of our research meetings and understands what we want. He has built and is marketing a machine in the United States that is, we feel, a better concept than the other machines.
What makes it better?
Dr. Lingeman: The original lithotripter, which we actually still use at Methodist Hospital—we’ve tried others; they haven’t worked as well so we kept the old one—has a very wide focus so that when the shock wave is targeted on the kidney stone, there’s a large area [receiving shock waves]. That makes it relatively easy to hit the stone. Most newer machines have very small focal zones, and because patients breathe and the kidney therefore moves during treatment, it becomes quite a challenge to keep the shock wave targeted on the stone. So that’s a problem.
A second problem is that the newer lithotripters have much higher pressures in their focal zone, and this is damaging to renal tissue, particularly if you’re missing the stone much of the time as you do with small focal zones.
What we’ve learned from our research is you don’t need these high pressures to break up kidney stones. The Lithogold, manufactured by TRT, employs a broad focal zone but with low pressures in the focal zone. It produces minimal tissue effects on the kidney, but still breaks up stones so it’s a better balance between safety and efficacy, in my opinion.
Where does flexible ureteroscopy fit into the picture?
Dr. Lingeman: Ironically, in the field of ureteroscopy, there have been steady advancements over the last two decades more along the lines of what we would expect to happen with medical technology. As the endoscopes that we’ve used have gotten smaller, they’ve gotten better. We have very good lasers and other devices that we use with these, and as it turns out, you can now basically treat most stones [with flexible ureteroscopy].
Ureteroscopy started around the same time as shock wave lithotripsy, and at that time our instruments were large and rigid—inflexible—so you couldn’t get them up into the kidney. You could only treat stones in the lower ureter. But now these instruments are flexible and they’re small. We can run them up into the kidney. Now, any stone that you can treat with ESWL, you can treat with flexible ureteroscopy and a laser. Ureteroscopes have become increasingly popular, and the technology is much, much less expensive than ESWL.