Incidence and Risk Factors for Urolithiasis in Patients with Crohn's Disease.

BACKGROUND: The incidence of urinary tract calculi is thought to be higher in patients with inflammatory bowel disease (IBD) than that in the general population. However, few data are available about urolithiasis in patients with Crohn's disease (CD). We investigated the incidence of urolithiasis and the risk factors for urolithiasis in patients with CD. METHODS: We examined the records of 387 patients with CD followed at Samsung Medical Center from July 2011 to June 2013. Evidence for the presence of calculi was obtained from radiologic findings (plain films, ultrasonography, or computed tomography), urinary colic symptoms, or a treatment history of urolithiasis after diagnosis of CD. Demographic variables, phenotype, concurrent medications, and previous CD-related surgery were analyzed. RESULTS: Urinary tract calculi were found in 18 (4.7%) patients, which developed after the CD diagnosis. The incidence of urolithiasis in CD was 706 per 100,000 patient-years. Cox models with a time-dependent covariate showed that azathioprine (AZA)/6-mercaptopurine (6-MP) treatment (hazard ratio = 0.963; 95% CI: 0.931, 0.996; p = 0.030) was negatively associated with urolithiasis. CONCLUSIONS: The annual incidence rate of urolithiasis in patients with CD was 0.7%. AZA/6-MP therapy was associated with a low risk of urolithiasis in these patients.