Major geogenic factors controlling geographical clustering of urolithiasis in China.

The prevalence of urolithiasis is increasing across the world and exhibits a distinctive characteristic of geographical distribution. Geographical clustering and major geogenic factors for urolithiasis prevalence in China were investigated. High risks of urolithiasis are found in southern China clustered in coastal provinces such as Fujian and Zhejiang and karst regions such as Sichuan, Chongqing, Guizhou, Guangxi, Guangdong, Hunan, and Hubei. The predominant urinary stone composition is a mixture of calcium oxalate and phosphate. We found that the spatial distribution of phosphate-type stones is closely related to that of phosphate ore deposits and carbonate rocks. Hot or warm climate and seasons increase the risk of lithogenesis through high average air temperature. Water and soil environment influence the quality and composition of drinking water and food, thus affecting stone formation in the urinary system. In particular, the increase of Ca(2+)/Mg(2+) ratio (in meq) in drinking water might be the main factor. Besides, the high content of calcium in local plants grown on karst soils and the intake of high oxalate food might contribute to the high prevalence in South China. This study indicates that urolithiasis could be endemic, with geogenic factors playing critical roles in urolithiasis etiology.