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Welcome to the Why Urology podcast with Dr. Todd Brandt.

This podcast is my personal attempt to teach you about your genito-urinary tract, what can go wrong, and how your urologist may just become your superhero.

The name of the podcast comes from my ongoing need to answer the question that I get so often from patients, friends, and family, “Why Urology? Why did you choose to become a urologist?”

Apr 16, 2017

episode 30—“I will not cut for stone.” In this episode we will revisit the shockwave lithotripsy procedure as a revolutionary procedure in urology and we explore how chance encounters can lead to urologic breakthroughs. If you remember from the last episode I introduced a story from when I was in college in 1986. In that story I remember one of my classmates telling me about an internship he had the prior summer doing research at a University Medical Center near his home. As chance would have it he University where he was working had just installed their first Dornier HM-3 shockwave lithotripsy machine, a machine that broke up kidney stones. The machine worked by passing shockwaves through the body to break up the hard stone without the need for an incision. The stone would be broken up into small particles that the patient would pass on their own. Just to keep in perspective how new this all was at the time the now iconic Dornier HM3 ESWL machine was developed in 1983. It was the first commercially available extracorporeal lithotripter in clinical application in the world. FDA approval for the HM3 was obtained in 1984 and the first HM3 was introduced in the United States in Indiana that same year. In 1986, only about two hundred Dornier lithotripters were installed worldwide and only about 250,000 treatments had been performed, and the first results began to be reported from the first few locations in the United States that had an HM3. The HM-3 lithotripter was a game changer. It allowed urologists treat kidney stones without making an incision. This advance, as well as the nearly simultaneous development in advances in scope technology allowed urologists to move away almost completely from making big incisions for the treatment of kidney stones today. We now have essentially 3 options for treatment for a patient that has formed a kidney stone and is unable to pass that stone on his or her own:

  1. Break up the stone using the shockwave lithotripter. “ESWL”
  2. Perform a scope procedure called ureteroscopy.
  3. Making a tract into the kidney directly through the back called a percutaneous nephrolithotomy “PCNL”

It would be the attraction of being able to use those new technologies and advances in medicine that would propel me to medical school and ultimately to the field of urology. And it keeps me going to work today. So it was with some excitement that I spent a recent Saturday in a conference at our state urological society meeting. The theme of this year’s annual conference was “innovations in urology.” This theme goes well with our last couple of episodes where we have talked about the celebration of the hundredth anniversary of the Journal of Urology chronicling the advances and innovations in Urology. All of the presentations were great, one speaker’s presentation at the conference stood out to me. As he talked about the process of innovation, the speaker used a personal example. He described himself as someone excited about life and about exploring new ideas. He described how he was always attending conferences or forums that may or may not relate directly to his field just to get ideas and to keep his brain stimulated. He described how when he was giving a presentation at one of those forums a few years ago he got in an argument with an audience member. This was the type of conference where this type of discussion was encouraged so instead of being offended, or angry, or holding too strongly to his convictions he asked the other man to eat lunch with him so they could discuss their differences further. To make a long story short urologic physician meets research physicist, physicist argues with physician, physician asks physicist to lunch, physician and physicist become good friends. Their friendship led to them exploring some avenues of research together, form a company, and through several years of work are now doing clinical trials on their research. Now that research may or may not pan out to something that becomes clinically significant, but what stood out to me was the urologist describing how much fun he and the physicist had working with each other, sharing ideas and developing a friendship out of it. Conflict led to conversation led to collaboration led to friendship. Awesome. Another one of the speakers at our conference showed a slide with an old saying that I think applies here: If you want to go fast, go alone. If you want to go far, take someone with you. It was one of the key takeaways for me from that day. Which brings me to another story I heard that day, and back to the HM-3. It relates to the invention and development of the shockwave lithotripsy and how the idea to explore that came about. I have mentioned before the process of discovery and research starting with a spark or idea.. In the case of the ESWL it was almost literally a spark that created the inspiration for the technology that we still use today. And it would take a team of people to move the research forward. In 1966, at the Dornier Aircraft Company in Germany engineers were studying what happens to aircraft as the aircraft travelled at supersonic speeds. As planes and as rockets began to go supersonic researchers discovered that pitting was taking place on the surface of an aircraft or rocket. The pitting damage on the windshields and exterior of the aircraft was felt to be a combination of both direct injury as well as cavitation bubbles created by soundwaves in combination with raindrops in the air. In their laboratory the researchers had built a small simulator to reproduce the effects they were seeing on the aircraft. Here is how the “spark” happened. As the story goes in both urology textbooks and on the website of the Dornier company a researcher who was using the machine just happened to have his hand in the machine and touched a metal plate in the machine the exact time that the sound-waves contacted the plate. He felt an electric shock. Inspecting his hand he found no external effects of the shockwave. That is that he felt the energy as a shock almost like electricity but there was no damage to the skin or any damage to his finger that he could see. This was, literally, shocking. The researchers at Dornier got to work. The Dornier engineers called up some urologists at a University in Munich, Germany and the team refined the process enough over years to apply for a government-backed research project in 1974. After several more years of innovation and research the first human trials of lithotripsy were performed between 1979 and 1981 on a machine called the HM or human model (HM)-1. The advances would come faster now between 1980 and 1983 when Dornier introduced the HM-3. The original HM-3 lithotripter was and is the Gold standard for lithotripters as far as stone fragmentation. Current generation machines are not necessarily better at breaking up stones the machines but have gotten smaller and easier to use, a water bath is no longer needed (just a balloon or bubble placed against the back through which the shockwaves pass), and the focal point or radius of greatest impact is significantly smaller which decreases the risk of damage to the kidneys or surrounding tissue. The United States had FDA approval of the equipment in 1984 in the first machine was installed in Indiana. By 1986 several machines had been employed in the United States and the procedure became commonplace enough that I would hear about it in a chance encounter hanging out with friends in a college dorm room. Through a series of chance encounters of my own I would end up at Vanderbilt Medical School, learn what a urologist was, and then go to the University of Iowa where, less than 10 years later in 1994 as an intern in urology I would “perform” the procedure for the first time. Perform is relative here as the machine does almost all of the work. But incidentally in 1994 I would not be using an HM-3 lithotripter. Even at that time most of those machines were no longer in service. I have never actually seen an HM-3 machine in person. So how does this actually all work? A shock wave is an acoustic pressure wave of short duration (<10 microseconds) with high peak pressure up to 100 megapascals (MPa) (approx. equal to 1000 atm of pressure) When a shockwave is propagated through a medium (water), it loses energy when it crosses into a medium with a different density such as a stone. This all works because the body tissues are relatively similar in density. Largely body tissues are water and so the passage of shockwaves through the body tissues is fairly consistent. The stone is much more dense because it contains very little water. When the shockwave travels from one medium to the next, compressive and tensile or expansion stress is created by the wave. Without going into the physics, mechanisms for stone fragmentation in include tear and shear forces, spallation, quasi-static squeezing, dynamic squeezing, super-focusing of reflected shockwaves. These mechanisms lead to cracks in the structure of the stone, and, as a result of repetition (the delivery of many shockwaves during a treatment) these cracks grow and accumulate over time, finally leading to stone disintegration. Cavitation also occurs. Remember the pitting effect that occurred on the windshields of planes and rockets. The same occurs on the surface of the stone. Cavitation is formation of bubbles at the point of impact that expand and contract forms a liquid jet (“micro-jets”) of high pressure and pitting on the surface of the stone. That’s enough physics. Let’s examine the procedure itself. Patients who are candidates for the shockwave procedure usually have a single stone within the kidney and the upper ureter. The stone size we treat is usually are 4-10 mm, although some larger stones can be treated. The stone can’t be too large because when the stones break up all those small fragments need to pass. Most patients who are treated in this way will be asymptomatic from their stone as the procedure is usually done electively on an outpatient basis. The stone must be visible by plain x-ray, what we call a KUB. Some stones cannot be seen on a plain x-ray. In most cases we use the plain x-ray images to locate the stone. If the stone is very dense on a plain x-ray it may be too dense for the shock waves to actually break up the stone given there’s a limit to the number of shocks that can be delivered to the body at any given time to avoid injury to the surrounding tissue. So in cases where we don’t think the stone will break up we would advise an alternative treatment. During the procedure a patient is put fully to sleep or is sedated heavily. The stone is located on the x-ray imaging in 3 dimensions and targeted and the patient is positioned on the machine so that the focal point of the shock wave is targeted on the stone. A series of shock waves are delivered to the stone. Careful attention is given to the patient to monitor for any complications during the procedure, such as cardiac dysrhythmias that can happen because of the shock waves. Stones are fragmented and the small fragments pass over the next couple of days to weeks through the ureter, bladder, and urethra hopefully without getting stuck along the way. Sometimes a stent is placed while the stones pass to help ensure that the urine is passing through the ureter as the stones pass. The ESWL procedure is generally considered safe, although as with any surgical procedure there are risks. The risks of the procedure include infections, bleeding, transient physiologic changes in the kidney as a result of the shockwave, and more serious risks of trauma and bruising to the kidneys and surrounding tissues, cardiac dysrhythmia, failure of breaking up the stone or failure of stone clearance or on the risks associated with the shockwave lithotripsy. Through many years of procedures the shock wave treatments have persisted as a great alternative for kidney stone treatment when the procedure is chosen for the right indication. Many, many years ago Hippocrates wrote and pledged an oath to not “cut for stone” but instead to leave it to others who were practitioners of the art. And for many years that was what urologists did, making large incisions to remove kidney stones. But somewhere in the early 1980s that changed dramatically with the technology changes such as the development of shock wave lithotripsy. But urologists didn’t do this alone. The advances came through chance encounters, collaboration, hard work, and maybe a few laughs along the way. And as the recent lecture I heard made clear, medical advances it continues to require chance encounters and collaboration even today. If you want to go fast, go alone. If you want to go far, take someone with you. END