By Michael Grasso, M.D.
Chief of Urology, St. Vincents Hospital
Professor of Urology at New York Medical College
All ureteral calculi, and in fact many stones throughout the caliceal system, can be accessed and treated in a retrograde fashion with a combination of various fiber optic endoscopes and powerful, precise lithotrites. In the early 1990’s improvements in fiber optic imaging and technical advances in endoscope design have allowed endurologists to place small fiberscopes through the urethra, bladder and into the upper urinary tract atraumatically. Various endoscopic lithotrites, including powerful laser lithotriptors, can be employed throughout the working channel of these endoscopes to treat calculi. In 1993 I began work on a small diameter flexible ureteroscope that measured approximately 2 mm in diameter and allowed access to the entire upper urinary tract. Shortly thereafter, a prospective study was instituted using a new laser energy–the holmium laser. This devise is a thermal laser which destabilizes stones into fine dust. The combination of this endoscope and lithotrite was able to clear 75 consecutive calculi in our most recent series. What is very interesting is that with other laser lithotripters, as the probes become smaller and more precise, the deliverable energy and efficiency decreases. This is not the case with the holmium laser.
Prototypic fibers as small as 2/10ths of a millimeter were designed and employed in this most recent series. As opposed to prior, larger fibers, these small fibers do not inhibit the deflectability of the endoscope and as such I’m able to access the entire caliceal system. Initially, I was only treating somewhat straightforward ureteral calculi. Most recently I’ve addressed a series of larger-branched stones in the caliceal system and I’ve been able to efficiently clear them.
This particular laser lithotriptor fragments all stones equally and efficiently as opposed to other devices including EHL (Electro-Hydrolic Lithotripsy) and the pulse dye laser which are less efficient fragmentors of cystine stones. The holmium laser basically vaporizes or destabilizes cystine stones into a fine powder. It works as efficiently on cystine as it does with other stone compositions.
I’ve recently treated a series of patients with large-branched calculi who had undergone multiple prior open and percutaneous procedures and now were searching for another modality which would obviate the need for long hospitalization and a percutaneous puncture. Most of these patients had undergone multiple courses of ESWL without success. Many of these patients were cystinurics and were quite frustrated with surgical intervention at this point. As excellent example is that of Ben Lokos who is a 33 year old cystinuric who has been suffering for many years.
Ben had undergone three prior percutaneous nephrostolithotomies on the left side and now is suffering with somewhat severe hypertension which most likely reflects perirenal and cortical scarring. I was able to access Ben’s large stone burden in a retrograde fashion and debulk a significant portion of it. We were also able to move the dust and remaining small fragments into portions of the collecting system that clear more easily after treatment.
Lower pole stones, that is those that are in a very dependent portion of the kidney, are less apt to clear after ESWL. With endoscopic therapy we can not only vaporize and remove a good portion of the stone, but are also often able to move or irrigate the remaining small fragments into other portions of the collecting system. It is in these other locations that they are more apt to pass easily. In Ben’s case, we cleared a significant portion of the stone burden in one sitting. As in most cases, this procedure is performed as an out-patient.
In summary, I think that the aforementioned techniques should be put clearly into perspective. The new equipment and the holmium laser are only in the hands of a minority of endurologists in the country. Also, the application requires a certain skill level and there is no question that there is a learning curve to this technique as there is with most minimally invasive surgical procedures. There are a handful of centers throughout the country where prospective studies are being done with these devices. The potential for a treatment that is done as an out-patient, able to clear large stone burdens–including cystine–efficiently, with minimal morbidity and significant efficiency gives promise to those cystinurics who have had multiple surgical interventions with mixed results.
A list of the following centers where retrograde interrenal surgery is performed with the holmium laser and small-diameter actively deflectable, flexible ureteroscopes:
- Michael Grasso, M.D., Associate Professor of Urology and Director of Stone Treatment and Prevention Center, New York University Medical Center, New York, New York
- Demetrius Bagley, M.D., Professor of Urology and Radiology at Thomas Jefferson University in Philadelphia, Pennsylvania
- Michael Conlin, M.D., Assistant Professor of Urology, Oregon Health Science Center, University of Oregon, Portland, Oregon
- Joseph Segura, M.D., Professor of Urology, Mayo Clinic, Rochester, Minnesota
- Gerhart Fuchs, M.D., Professor of Urology, UCLA Medical Center, Los Angeles, California
- Kent Kirby, M.D. at the Cleveland Clinic in Florida.