Emergency department (ED) visit rates and the use of computed tomography (CT) for urolithiasis have been increasing in the United States, new findings show.

The increase in ED visits has been greater among women than men and greater among whites than non-whites.

“The increase in ED visits with urolithiasis diagnoses might result from a combination of factors including an actual change in disease incidence, improvement in diagnostic methods, and/or an increase in the number of people who use the ED for primary medical care,” investigators wrote in an online report in Kidney International.

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Investigators led by Ziya Kirkali, MD, of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md., found that ED visit rates rose from 178 to 340 per 100,000 individuals from 1992 to 2009, a 91% increase. Among female patients, the ED visit rate increased from 127 to 289 per 100,000 individuals, a 128% increase. By comparison, the rate among male patients increased from 231 to 393 per 100,000, a 70% jump. Among whites, the rate rose from 191 to 384 per 100,000 individuals, a 101% increase; among non-whites, the rate increased from 112 to 165 per 100,000 individuals, a 47% increase.

Among the various age groups examined in the study (younger than 25, 25-44, 45-64, and older than 64 years), patients aged 25-44 years had the largest increase in ED visit rates: from 258 to 599 per 100,000 individuals, a 132% increase.

The proportion of urolithiasis patients imaged with CT increased from 21% in 1998-2000 to 71% in 2007-2009.

“The increased use of CT for evaluation of a common clinical syndrome such as urolithiasis raises important clinical questions,” the researchers wrote. “CT clearly provides important and accurate diagnostic information for physicians caring for patients with suspected urolithiasis. However, repeated use of CT evaluations for patients with recurrent urolithiasis contributes to increased radiation exposure for patients, as well as an increase in costs.”

The researchers identified these trends by analyzing data from the National Ambulatory Medical Care Survey and the National Health and Nutrition Examination Survey (NHANES). Their study also showed that medical expulsive therapy was used by in 14% of patients with a urolithiasis diagnosis in 2007-2009. Among NHANES participants who reported a history of kidney stones, 22.4% had passed three or more stones.

The study revealed no seasonal or regional variation in ED visit rates for urolithiasis during the study period.