Objective: Urolithiasis is a common urological problem, and its incidence has been increasing worldwide, including in Japan. Relationships between stone etiology and rise in ambient temperature have been reported, but it remains unclear how age and gender affect these relationships.
Materials and methods: A retrospective examination was conducted of the medical archives of 1005 patients (aged ≥15 years) with acute renal colic diagnosed with urolithiasis upon image examination who consecutively visited emergency departments in three hospitals. The patients were categorized into six groups according to age: younger than 30, 30-39, 40-49, 50-59, 60-69, and 70 years and older. The net difference and fold increase in the number of patients in summer (July to September) versus in winter (December to February) were calculated.
Results: Overall, the actual number of the patients varied according to the temperature rise throughout the year and among the age groups. Net increases in the number of patients were observed in all age groups for both genders, apart from 30-39-year-old women. The age group of 50-59 years considerably outnumbered all other groups. A significant statistical correlation was detected between the fold increase and male aging using Spearman's rank correlation analysis (ρ = 0.94, p = 0.017), but not in females (ρ = -0.03, p = 1).
Conclusions: These results support a positive association between ambient temperature rise and increase in the incidence of renal colic due to urolithiasis in Japan, and indicate that aging and gender affect the association differently.
Keywords: Elderly; male; renal colic; temperature; urinary stone.