Risk factors for CKD in persons with kidney stones: a case-control study in Olmsted County, Minnesota.

BACKGROUND: Kidney stones are associated with increased risk of chronic kidney disease (CKD); however, risk factors in the general community are poorly defined.

STUDY DESIGN: A nested case-control study was performed in residents of Olmsted County, MN, who presented with a kidney stone at the Mayo Clinic in 1980-1994 to contrast patients with kidney stones who developed CKD with a group that did not.

SETTING & PARTICIPANTS: Participants were selected from the Rochester Epidemiology Project, an electronic linkage system among health care providers in Olmsted County, MN. Cases were identified by diagnostic code for CKD and confirmed to have an estimated glomerular filtration rate < 60 mL/min/1.73 m(2). Controls were matched 2:1 to cases for age, sex, date of first kidney stone, and length of medical record.

PREDICTOR: Charts were abstracted to characterize stone disease, hypertension, diabetes, obesity, tobacco use, ileal conduit, symptomatic stones, type and number of stones, urinary tract infections, number and type of surgical procedures, and medical therapy.

OUTCOMES & MEASUREMENTS: Kidney stone patients with CKD were compared with matched stone patients without CKD.

RESULTS: There were 53 cases and 106 controls with a mean age of 57 years at first stone event and 59% men. In kidney stone patients, cases with CKD were significantly more likely (P < 0.05) than controls to have had a history of diabetes (41.5% vs 17.0%), hypertension (71.7% vs 49.1%), frequent urinary tract infections (22.6% vs 6.6%), struvite stones (7.5% vs 0%), and allopurinol use (32.1% vs 4.7%) based on univariate analysis.

LIMITATIONS: Potential limitations include limited statistical power to detect associations, incomplete data from 24-hour urine studies, and that stone composition was not always available.

CONCLUSION: As in the general population, hypertension and diabetes are associated with increased risk of CKD in patients with kidney stones. However, other unique predictors were identified in patients with kidney stones that increased the possibility of CKD. Further studies are warranted to elucidate the nature of these associations.