A new tool may predict the likelihood that a patient who has a first kidney stone may have a second, according to a study published online August 7 in the Journal of the American Society of Nephrology.
The Recurrence of Kidney Stone (ROKS) nomogram may help physicians determine which patients are at high risk for recurrence and would most likely benefit from medication, radiographic monitoring, or restrictive diets to prevent painful episodes and long-term complications such as kidney failure. At the same time, this knowledge could spare low-risk patients the cost of tests, potential harm from medications, and onerous limitations on what they can eat.
The tool, developed by Andrew Rule, MD, from the Division of Nephrology and Hypertension, Department of Medicine and Division of Epidemiology, Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota, and colleagues, evaluates several factors including patient characteristics and the stone’s composition and location.
The authors analyzed medical records from all 2239 adults treated for their first stone in Olmstead County, Minnesota, between 1984 and 2003 who had evidence of a passed, obstructing, or infected stone causing pain or gross hematuria.
Of those individuals, 707 patients had a recurrence during the study period, which continued through 2012. Recurrence rates at 2, 5, 10, and 15 years were 11%, 20%, 31%, and 39%, respectively.
First-time stone-formers were more likely to have another episode if they were young, white males with a family history of kidney stones, had blood in their urine, had stones made of uric acid, had an obstructing stone in the renal pelvis, or had additional nonobstructing stones.
Because many who have a first stone have a relatively low risk for a second symptomatic episode, tests and treatment are often limited, and many patients do not get 24-hour urine studies or medications until they have several painful episodes, researchers said. They hope ROKS will help the high-risk patients receive appropriate treatment sooner.
Tests in Warmer Climate Will Be Important
In an accompanying editorial, Brian Eisner, MD, from Massachusetts General Hospital in Boston, and David Goldfarb, MD, from the New York Harbor Veterans Affairs Healthcare System and New York University School of Medicine, New York City, said the nomogram gives valuable data and should be tested prospectively in warmer climates.
“Kidney stone prevalence is greater in warmer climates presumably because higher ambient temperature leads to reduced urine volume and higher concentrations of stone-forming salts,” Dr. Goldfarb told Medscape Medical News. “On the basis of previously published data and the current nomogram, it follows that stone recurrence in Rochester, Minnesota, where monthly average high temperatures are <4.4°C for 7 months per year, may actually underestimate recurrence rates in lower latitudes and warmer climates.”
He noted that the ROKS nomogram may help motivate first-time stone-formers to drink more liquids, increase dairy consumption (if needed), and reduce salt intake.
He likened the potential benefit to that of FRAX, the World Health Organization’s bone nomogram that helps target treatment for osteoporosis.
“It’s too early to expect ROKS to be the equivalent, because it will have to be tested prospectively and in populations other than that of Olmsted County,” Dr. Goldfarb said. “But I think it’s a useful beginning.”