“A wild and woolly time”: Extracorporeal shock wave lithotripsy for kidney stones

James E. Lingeman, MD

Urology Times® is celebrating its 50th anniversary in 2022. To mark the occasion, we are highlighting 50 of the top innovations and developments that have transformed the field of urology over the past 50 years.In this installment, James E. Lingeman, MD, discusses the development of extracorporeal shock wave lithotripsy for the treatment of kidney stones. Lingeman is a professor of clinical urology at Indiana University School of Medicine in Indianapolis.

Could you provide an overview of the development of ESWL for the treatment of patients with stones?

The machine was developed by the aerospace company Dornier. They had a couple of "mad scientists," if you will, working in the basement: an engineer named Wolfgang Hepp and a physicist named Bernd Forssmann. Dornier noticed patterns of undue metal fatigue in some of their jet aircraft. They hypothesized that this was due to shock waves that were being focused on certain parts of the fuselage, causing premature metal fatigue. They sought to create a system to reproduce the shock waves so that they could study the problem. They had contracts with the German military to develop some of this. Supposedly, as the story goes, the engineers and physicists were at a cocktail party, discussing this work and one of their wives said, "Why don't you use this to treat kidney stones?" So Hepp and Forssmann literally started in the basement with a grant from the German government to study this, and it progressed through till the clinical machine was introduced.

The first human was treated in Germany in 1980, with what was called the HM1. "H" was for "human" and "M" was for "machine," so it was Human Machine 1. They had other machines before that, but those were for animals. HM2 followed, and eventually, the first commercial machine was the HM3. That's the machine that I used to treat the first patient in the United States in February 1984. That was a very famous machine. It truly revolutionized the treatment of patients with kidney stones. Prior to that, pretty much everybody that had a stone that couldn't pass had open surgery. After that, almost no one did. It was one of the more dramatic changes in the surgical practice of urology that's ever occurred. A lot of urologists in that era did not believe that this was possible or that this would work. The idea that you could break a stone up and that the patient could pass all the pieces spontaneously, without any help, was just too radical for most people to get their heads around. But it did work and it worked remarkably well. It was a very historic device in that regard. It really changed people's attitudes in urology about new technology, and for everything that came afterwards in urology, people were open to it because of the success of the dramatic nature of the of the Dornier lithotripter.

What makes ESWL an innovation in urology?

The seminal innovation was the idea that you could create a focused shock wave that could be delivered into the body in a non-invasive way that had sufficient energy to break up a stone but not damage other structures.

How has ESWL improved the treatment of patients with stones?

In the early 1980s, there were a few people, myself included, who were doing some percutaneous procedures to remove stones. We didn't have ureteroscopes of any sort. The first ureteroscope was introduced in the United States in late 1983/early 1984. With the lithotripter, you had this machine that could avoid the need for open surgery. This was very dramatic. When we had the first machine, we had patients calling from all over the world wanting to come get treated. It was a wild and woolly time.

The HM3 was a very large device with a large water bath. The patient was immersed in a water bath, which provided a very effective coupling mechanism of the shock wave to the body. We humans are mostly water, and so the acoustical impedance of the skin, fat, tissue, etc, is very similar to that of water. A shock wave generated underwater will transmit into the body without losing a lot of its energy. Right away, other companies recognized the innovation and the success of Dornier with this device, so they began to build machines. They perceived the water bath to be very cumbersome, and so what they did was on the shock wave generator, they just put a cushion, which was then coupled to the patient with ultrasound gel. That eliminated the water bath. That did work, but not as well as the HM3.

If you look at a computer from the 1980s, compared to what we have now, things have evolved dramatically in a positive way. Lithotripsy is a notable exception to that. The newer lithotripters do not work as well as the original. Generally, because of their design, they do not break stones up as well as the original HM3. We've had a grant from the National Institutes of Health for almost 30 years looking at the basic science of lithotripsy. Dornier, when they introduced this machine, didn't really understand the basic science of how the shock waves broke up stones. They were very fortunate in that the system that they designed worked incredibly well. But when companies decided that they wanted to try to change the machine to the next generation, they made changes without really understanding how the machine worked at the basic science level, and so all those decisions were not helpful in terms of making the machine work better. So with lithotripsy, the machines have not improved; they work less well than they did 30 years ago.

However, we now have remarkable ureteroscopic instrumentation. We have the holmium laser, which will break up 100% of stones. There's also the thulium laser, which may or may not be any better; it's hard to beat 100%. We can, with a flexible ureteroscope and laser, now treat any stone up in the kidney that we could treat with lithotripsy. We also, of course, have the percutaneous operation. Back in 1983/1984, when I started doing those, it was a messy operation. We didn't have the equipment that we have now. But the techniques now are all very refined and very effective. What you see, all around the world, is a steady decline in the percentage of stone patients that are being treated with lithotriopsy. In 1984, almost 100% of them were treated with lithotripsy because we didn't have good alternatives. But as these other technologies have developed, and as lithotripsy has diminished in its efficiency, more and more patients with kidney stones are being treated with therapies other than lithotripsy. The lithotripter is a big piece of equipment. Not every hospital has one. Every hospital can afford to have a flexible ureteroscope; they're even disposable now. If a patient comes in to the emergency room in the middle of the night, you don't have to wait 2 weeks for the truck to arrive with the lithotripter on it.

It's a bit of an unusual story of medical technology. We always expect things to get better. But that was not the case with lithotripsy. The HM3 was built like a Mercedes; they lasted for decades. I think they're all pretty much gone now. People that had them held onto them for dear life, because they were better than everything else. I don't know why somebody doesn't make one again.