Risk of UTI in kidney stone formers: a matched-cohort study over a median follow-up of 19 years.

PURPOSE To describe risk of UTI in Stone formers comparing to non-stone formers. METHODS Retrospective cohort study using electronic records for patients across southern England. Stone formers referred to a tertiary referral centre in Southern England, comparator patients were age and sex matched with 3:1 ratio from same database. Those with no documentation were excluded. UTI defined using ICD-10 codes. Risk of UTI presented as hazard ratio with 95% confidence interval, generated using cox regression. Sample size calculated using 80% power and significance set at 0.05. RESULTS Eight hundred and nineteen stone formers were included after 1000 records were screened for inclusion, with 2477 age and sex matched non-stone formers extracted from the same database. Sample size was calculated at 287 per group. Stone formers were at significantly increased risk of developing a UTI (HR 5.67; 95% CI 4.52-7.18, p < 0.001). Median follow-up was 19 years (IQR: 15-22). CONCLUSIONS Kidney stone formers are at increased risk of developing urinary tract infections.