Kidney stones linked to greater chance of CKD

A study presented at a nephrologists' conference last month has provided scientific evidence to support what many physicians have long suspected. Patients who develop kidney stones are more likely to develop chronic kidney disease and end-stage renal disease.

"Kidney stones are not a traditionally recognized risk factor ... but clinicians know it," said Dr. Rajiv Saran, associate professor and director of the Kidney Epidemiology and Cost Center at the University of Michigan, Ann Arbor.

The paper presented at Renal Week 2008, the American Society of Nephrology's 41st Annual Meeting and Scientific Exposition in Philadelphia suggested that those with a history of kidney stones had a 60% increased risk of developing CKD when compared with a healthy control group. The additional chance of ESRD was 40%. Those with stones also had a 40% increased risk of having an elevated serum creatinine or a reduced estimated glomerular filtration rate.

The authors say this finding adds importance to strategies to avert kidney stones in those who tend to form them, such as prescribing certain medications or recommending dietary changes.

"This should tell us to be a little more vigilant and think about treating patients to prevent kidney stones," said John Lieske, MD, lead author and professor of medicine at the Mayo Clinic in Rochester, Minn.

But those researching this area also expressed caution in interpreting these findings. This epidemiological study showed an association, but not cause and effect. It's unclear why these two conditions would be linked.

"The issue is, 'is this real and why?' It's an intriguing observation that needs to be followed up," said Anton C. Schoolwerth, MD, a nephrologist and professor of medicine at Dartmouth-Hitchcock Medical Center in Lebanon, N.H.

Some experts theorize that the stones themselves, or treatment to destroy them, may cause damage that later progresses to CKD and ESRD. Or it may start earlier. The process of stone formation may begin the cascade, but this association also may be because the same medical conditions that increase the chance of stones also increase the possibility of these other problems.

"It could be that there are common risk factors," said Gary Curhan, MD, ScD, a nephrologist and physician investigator at Brigham and Women's Hospital in Boston. "[Kidney stones] may not be causal."

But while the link between kidney stones and kidney disease is an open question, the fact that problems with this organ are becoming more common is not. The number of people affected has grown by 30% over the past decade. Most will die of cardiovascular disease before the kidney fails, although ESRD also increased by 3.4% from 2005 to 2006. In response, the U.S. Renal Data System last month issued its first report on the subject, in conjunction with its annual paper rounding up ESRD statistics. About 27 million people have CKD. The condition accounts for 24% of Medicare costs. The ESRD population makes up about 1% of the Medicare population and 7% of the program's costs.

"The major focus on chronic kidney disease in this year's report acknowledges that this disorder is a growing public health issue deserving of wider public awareness and intensified scientific investigation," said Elias A. Zerhouni, MD. He was director of the National Institutes of Health at the time the report was issued.

CKD also is a subject of growing public health surveillance efforts and medical society attention. In June, the American Medical Association passed policy at its Annual Meeting in Chicago that called for the U.S. Preventive Services Task Force to consider developing guidelines on the screening, diagnosis and staging of the condition.