Technological advances have enabled the increasing application of flexible ureteroscopy for stones.
CLEVELAND—A shift away from shock-wave lithotripsy (SWL) and toward flexible ureteroscopy is changing the landscape of stone disease treatment, said Mihir M. Desai, MD, during the Cleveland Clinic’s Nephrology Update 2008.
The enthusiasm for SWL at many academic centers in the United States is waning as new-generation compact lithotriptors are less successful at stone fragmentation compared with the earlier Dornier HM3, said Dr. Desai, Director of the Stevan B. Streem Center for Endourology, Glickman Urological and Kidney Institute of the Cleveland Clinic, and associate professor of surgery at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University.
This is because of attempts to reduce SWL’s effect on surrounding tissue by reducing the focal zone and the persistence of long-term safety concerns with shock-wave delivery.
The preferred methods for treating renal stones at the Cleveland Clinic, as in many other centers, are now percutaneous nephrolithotomy (PNL) for larger calculi and flexible ureteroscopy for small- to medium-sized renal calculi, he said. “Second and third generation flexible ureteroscopes are smaller, have greater deflection and can reach more areas of the urinary tract,” he said.
SWL safety concerns
SWL may pose certain safety concerns. In a 19-year follow-up of patients undergoing SWL for renal and proximal ureteral stones, Krambeck and colleagues found significantly increased risks of hypertension and diabetes compared with controls, even after adjusting for BMI, Dr. Desai noted.
Limitations of this study included its retrospective nature, the 59% response rate from the original series, the use of a first-generation (Dornier HM3) lithotriptor in all cases, and the lack of a clear causal relationship between SWL and hypertension and diabetes.
Recent research, however, has found an elevation of pancreatic enzymes in patients undergoing SWL, establishing a potential link between it and the development of diabetes, Dr. Desai noted.
Japanese investigators found no such link between SWL of renal stones and hypertension or diabetes. Even though the association of SWL and diabetes currently remains controversial, the potential for diabetes should be factored into counseling of patients when explaining options for the treatment of kidney stones, he said.
A poor response to lithotripsy has been observed with certain stone characteristics. Predictors of a poor response are greater stone density, a greater stone-to-skin distance, and a larger stone volume.