Probiotic treatment, new lithotriptor highlight stone advances

August 15, 2005

From surgical techniques to genetic manipulation, researchers continue to find new and novel ways to deal with the age-old problem of stone disease. Urologists are now better equipped to deal with the condition than they have ever been, said Glenn M. Preminger, MD, professor of urology and director of the Comprehensive Kidney Stone Center at Duke University Medical Center, Durham, NC.

Dr. Preminger identified the following stone-related take-home messages from the AUA annual meeting and explained why urologists should take note of each one of them.

Oxalate degradation by recombinant lactic acid bacteria could serve as a basis for a potential probiotic treatment of hyperoxaluria.

That led Ben H. Chew, MD, an endourology fellow, and his colleagues from the University of Western Ontario, London, Canada, to consider another approach. In an animal model, they cloned and expressed an oxalate decarboxylase gene from Bacillus subtilis into the bacterium Lactococcus lactic, which can be safely ingested by humans. The L lactis bacterium degraded more than 90% of available oxalate in one sample in just 30 minutes.

"It's extremely early, and this is just an animal study, but the results suggest that lowering intestinal oxalate levels may eventually give us another method of treating patients with oxalate stones," Dr. Preminger explained.

Researchers have documented a marked increase in the rate of females discharged for stone disease since the mid-1990s.

It is no secret that the overall prevalence of stone disease in the United States is on the rise. Interestingly, though, investigators from Duke University reported a 15.6% increase nationally in the rate of females discharged for kidney and ureteral calculi from 1997 to 2002.

Changes in diet and lifestyle may explain why the ratio of stone formation has now changed to about 1.3 males for every female, according to Charles D. Scales, Jr, MD, who performed the study.

Dr. Scales and colleagues speculate that diet and lifestyle are the main factors influencing the rise in female nephrolithiasis. They noted that the typical Western diet, which includes high levels of meat-based protein, is a "very significant risk factor for stones."

"Obesity is a major health problem in the U.S., and it is more problematic in women," Dr. Preminger said. "That's likely one reason we're seeing more stones in females."

Endoscopic procedures performed after failed shockwave lithotripsy have lower success rates and are associated with increased morbidity.

A group from Israel examined 93 patients who had undergone endoscopic treatment for renal calculi. Those whose endoscopy was conducted as first-line therapy did significantly better than those who had been initially treated with shock wave lithotripsy.

"By better selecting your first procedure and not using shock wave lithotripsy to treat everybody who walks through the door, you can achieve far better results," said Dr. Preminger. "Basically, it is more difficult to 'clean up' residual stone fragments left behind after a failed lithotripsy procedure."

Upper-pole puncture with use of a lower-pole nephrostomy tube is an efficient way to treat complex stone disease with relatively few associated complications.

Many urologists are reluctant to undertake upper-pole renal access as part of percutaneous removal of large or complex stones because they're wary of the associated morbidity. But James Ng, MD, and colleagues from the Methodist Hospital, Indianapolis, experienced only seven complications among 62 patients using upper-pole access with concomitant placement of a nephrostomy tube through a lower-pole calyx.