Regional short-term climate variations influence on the number of visits for renal colic in a large urban Emergency Department: results of a 7-year survey.

The pathogenesis of renal stones is an intricate process and varies widely depending on the composition of stones. There is also a marked geographic variability, strongly attributable to the mean annual temperature (MAT) and, to a lesser extent, on the seasons. Previous investigations report peaks in Emergency Department (ED) visits for renal colic during the summer. The aim of the present investigation is to assess the influence of day-by-day climate changes on the number of visits due to renal colic in our ED (city of Parma, located in the Po river valley, with a temperate continental climate). A total of 8,168 colic episodes were retrieved from our database during a period of 2,557 days (from 1 January 2002 to 31 December 2008). Over the same period 557,990 patients were admitted to our ED, renal colic visits representing 1.46% of the total. The linear regression analysis fitting the mean number of colic visits per day and the mean daily temperature displays a very high and significant correlation (R = 0.88, p < 0.0001). A multiple linear regression analysis between the mean temperature of each of the 30 days preceding the colic episode also shows strong correlations, being the strongest on the 5th-7th days (R = 0.80, p < 0.0001 on the 6th day before the colic episode), and a weaker but highly significant correlation on days 14 (R = 0.77, p < 0.0001) and 20 (R = 0.70, p < 0.0001) before the colic episode. Taken together, these findings suggest a kind of "acceleration" process of stone formation caused by the hot climate and, perhaps, by dietary variations during the summer. This process might trigger a sudden growth of the stone and, finally, the resulting clinical episode.