Kidney stones are common and are on the rise, according to government statistics. About 11% of U.S. men and 6% of women develop urolithiasis once or more during their lifetime, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Recurrence is common, too—occurring at a rate of up to 50% within the first 5 years of the first stone episode, researchers reported in an article published Feb. 25, 2016 in Nature Reviews Disease Primers.
Despite the high prevalence of kidney stones and recent AUA guidelines to medically manage them, urologists don’t do a very good job at managing stone patients, according to Kyle Wood, MD, assistant professor of urology at University of Alabama at Birmingham.
“We’re very good at surgically treating stones, and we’ve had significant advancements within the surgical realm with equipment and lasers and optics,” Dr. Wood said. “But we’ve done a pretty poor job as a practice at managing kidney stones and advancing our field in regard to medical management. I think the biggest issue is we haven’t even followed our guidelines.”
Brian R. Matlaga, MD, MPH, professor of urology and director of The Stephens Center for Stone Disease at Johns Hopkins University School of Medicine in Baltimore, said there is good evidence that medical therapy reduces future stone events. But the evaluation can be cumbersome, primarily from the patient’s standpoint.
“The 24-hour urine collection is a cumbersome type of a test to do,” Dr. Matlaga said. “The interpretation of it has become easier in recent years with commercial laboratories that provide some guidance for therapies based on reported lab results. But still it requires ultimately a urologist to prescribe medication and then follow the patient to assess how effective those medications are in reducing their risk factors.
“It brings the patient to a longer-term relationship with the physician than just someone that shows up, has a symptomatic stone, the stone is removed, and then the relationship is over.”
Another real-world challenge in medical stone management is the lack of innovation aimed at reducing stone risk.
“The medications we’re using today in 2020 are the same medications that were used 2 and 3 decades ago,” Dr. Matlaga said. (Also see, “New agents may offer hope for two forms of hyperoxaluria.")
Nevertheless, urologists can optimize the care they provide kidney stone patients by leveraging best practices in guideline documents, including the AUA’s Medical Management of Kidney Stones guideline, which Dr. Matlaga and other authors reviewed and updated in 2019.
The first evidence-based steps
Guideline first author Margaret S. Pearle, MD, PhD, vice chair of urology and professor of urology and internal medicine at UT Southwestern Medical Center in Dallas, said urologists first need to determine which stone patients need further evaluation.
“We really want to identify the high-risk patients,” she said. “We typically do a screening evaluation that consists basically of a careful history looking for any underlying conditions that are associated with stones, a family history of stones, any medications that are associated with stone production, and blood work. Blood work can identify some medical conditions like renal tubular acidosis or primary hyperparathyroidism that are associated with recurrent stones.”
Dr. Wood said research at University of Alabama suggests about 7% of the kidney stone population has primary hyperparathyroidism and about one-fourth of those patients are misdiagnosed or not diagnosed by the providers who referred them to the academic center.
If the history and blood work fail to uncover any risk factors in a patient who has had only one stone, Dr. Pearle said she makes general dietary recommendations but doesn’t do full metabolic testing. She does recommend full metabolic testing, including one, preferably two, 24-hour urine tests and blood work for patients who have recurrent stones or risk factors in their history.
“In those patients in whom we obtain a 24-hour urine, we look at all the parameters—total volume, pH, calcium, oxalate, uric acid, citrate, sodium—the important parameters of the urine that give us indications of underlying causes. We make recommendations based on those results,” Dr. Pearle said. “Some abnormalities can be managed with dietary measures, some require medication, and often it’s a combination of both.”