INFLUENCE OF SEASON, AGE, AND SEX ON RENAL STONE FORMATION IN SOUTH-AUSTRALIA

Objective: To investigate trends in renal stone formation in the South Australian population, between 1977 and 1991 (3634 stones), with respect to age, sex and seasonal variation. Results: The frequency of the different stone types was: calcium oxalate (with or without phosphate), 68%; uric acid, 17%; infection stones (magnesium ammonium phosphate), 12%; and pure calcium phosphate, 3%. No significant seasonal variation was observed with calcium oxalate or calcium phosphate stones. The incidence of uric acid stones increased significantly during summer and autumn (P < 0.001 and P < 0.01 respectively), and that of infection stones decreased significantly during spring and summer (P < 0.05 and P < 0.01 respectively). Calcium oxalate, uric acid and calcium phosphate stones were more frequent in male subjects; male to female ratio 2.8:1, 3.7:1 and 1.4:1 respectively. However, there was an increased frequency of calcium oxalate stones in women 20 to 25 years of age; male to female ratio 0.7:1. Infection stones were more common in female subjects; male to female ratio 0.7:1. Conclusions: This study demonstrates significant seasonal variation in uric acid and infection stones. Men are at a higher risk of forming stones than women, with the exception of infection stones. Additionally, with calcium oxalate stones, women may have distinct periods of higher risk. This study confirms that calcium oxalate stones are the most common stone type, which is in accordance with studies from other industrialised countries.