Stone studies examine genetics, prevention, removal

Studies on the etiology and management of stone disease that will be presented at the upcoming AUA annual meeting will advance urologists' understanding of the genetic and dietary origins of stones, describe the basic physics of shock wave lithotripsy and additional technologies used to improve SWL results, and demonstrate new techniques and refined technologies that enhance percutaneous and ureteroscopic approaches during stone removal, according to Glenn M. Preminger, MD, director of the Comprehensive Kidney Stone Center at Duke University Medical School, Durham, NC.

"We are gathering valuable information about the roles of genetics and diet in stone disease that will eventually lead to better risk assessment, new preventive measures, and, further down the road, genetically based therapeutic interventions," Dr. Preminger told Urology Times.

Every year, studies are reported on the effects of diet on stones and the frequency of stone formation. This year is no different. At least two investigations suggest lemonade may produce benefits in patients who form calcium oxalate stones and who have have mild to moderate hypocitraturia.

The importance of environmental processes that affect stone formation also will be discussed during studies investigating the long-term effects of bariatric surgery.

Treatment innovations

A host of studies will explore the physics of stone fragmentation and tissue injury, with emphasis on maximizing the former and minimizing the latter. The goal of this work is to make shock wave lithotripsy more effective and safe, Dr. Preminger explained. The importance of achieving these goals is highlighted by a controversial study published in the Journal of Urology (2006; 175:1742-7) that suggested that shock wave lithotripsy may be linked to hypertension and elevated risk for diabetes after many years of follow-up.

The controversy sparked by publication of this study will undoubtedly continue through the AUA meeting and beyond, Dr. Preminger said.

A number of studies will assess ways to improve stone removal. Several investigations suggest that administration of alpha-adrenergic blockers in conjunction with shock wave lithotripsy facilitates stone clearance, Dr. Preminger said. It follows, he said, that the drugs also improve quality of life.

"In addition, there will be a number of studies exploring percutaneous stone removal techniques, especially those directed at removing larger stones," he added. "At least one of these studies suggests that post-operative morbidity may not be linked to the size of the nephroscope but how long the percutaneous nephrostomy tube remains in place following the procedure."

Studies will also demonstrate improvements in ureteroscopic technology and techniques. Data on improved flexible ureteroscopes will be shown, along with a trial that compares ureteroscopy to shock wave lithotripsy.

The overall message is that SWL is good; it's a useful, improving technology, but the flexible ureteroscopy may be a safer and more efficient technology, at least for the time being, Dr. Preminger suggested.