MILAN—Emergency department visits for kidney stones in the U.S. have increased, especially among women, but admission rates for kidney-stone patients have remained stable, according to study findings presented at the 28th annual congress of the European Association of Urology.

From 2006-2009, the estimated incidence of ED visits among women increased by a significant 2.85% annually, compared with a non-significant 1.19% annual increase among men.

The study also showed that the overall incidence of ED visits for kidney stones was highest in July and August (24.74 and 25.18 per 100,000 person-years, respectively) and lowest in February (17.40 per 100,000 person-years).

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Study investigator Khurshid R. Ghani, MD, a urology fellow at the Vattikuti Urology Institute, Henry Ford Health System, Detroit, said increased use of medical expulsive therapy for kidney stones—which only came into wide use in recent years—could explain why kidney-stone-related hospital admissions have not risen even though ED visits for kidney stones has increased.

Dr. Ghani and his colleagues analyzed 2006-2009 data from the Nationwide Emergency Department Sample, the largest all-payer ED database in the U.S. The study looked at 3.6 million ED visits with upper urinary tract calculi as the primary diagnosis.

The study by Dr. Ghani’s team echoes those of a recently published study in Kidney International by Ziya Kirkali, MD, of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md., and colleagues. The study, which relied on data from the National Ambulatory Medical Care Survey and the National Health and Nutrition Examination Survey, found an increasing ED visit rate for kidney stones in the U.S., and showed that the ED visit rate increased to a greater extent among female patients than male patients. From 1992-2009, ED visit rates overall increased from 178 to 340 per 100,000 individuals, a 91% increase. Among female patients, the ED visit rate increased from 127 to 289 per 100,000, a 128% increase. By comparison, the rate among male patients increased from 231 to 393 per 100,000, a 70% jump.