Factors Associated with Compliance to Increased Fluid Intake and Urine Volume Following Dietary Counseling in First-Time Kidney Stone Patients

Objective: Increasing fluid intake to achieve a urine volume (UV) of >2.5 L/day decreases stone events. We assessed compliance rates and demographic and clinical variables associated with increased fluid intake and UV in patients with urolithiasis following dietary counseling.

Materials and methods: In a retrospective study, patients with a low baseline UV (<2.5 L/day) on an initial 24-hour urine collection during metabolic stone evaluation were identified between 2010 and 2015. Patients received detailed standardized dietary counseling, including increasing fluid intake to >3 L/day and titrating it to achieve UV >2.5 L/day. A follow-up 24-hour urine collection was performed at 6 months (FU1) and 18 months (FU2) to assess compliance (UV >2.5 L/day) and predictors associated with it.

Results: Our cohort contained 363 patients, 53.4% men and 46.6% women. The mean UV of baseline, FU1, and FU2 urine collections was 1.63, 2.52, and 2.48 L, respectively. The compliance rate of obtaining UV of >2.5 L was 50.1% at 6 months. On logistic regression, male sex (odds ratio [OR] 3.27, 95% confidence interval [CI] 1.94, 5.52, p < 0.001), urolithiasis-related procedures such as ureteroscopy (OR 2.31, 95% CI 1.20, 4.42, p = 0.01) or percutaneous nephrolithotomy (OR 3.48, 95% CI 1.58, 7.63, p = 0.002), and baseline 24-hour UV >1 L (OR 3.00, 95% CI 1.02, 8.76, p = 0.04) were associated with greater odds of compliance. Age >58 years (OR 0.39, 95% CI 0.20, 0.75, p = 0.005) and presence of lower urinary tract symptoms (OR 0.50, 95% CI 0.26, 0.95, p = 0.03) were associated with lower odds of compliance. Ethnicity, body mass index, renal function, marital status, renal stone burden, stone type, and household income were not associated with compliance.

Conclusions: In stone formers, compliance to fluid intake recommendations as measured by 24-hour UV is roughly 50%. Understanding risk factors for noncompliance, especially in at risk patients, can be used for quality improvement initiatives and reducing stone events.