Compliance in patients with dietary hyperoxaluria: A cohort study and systematic review.

Objective: Hyperoxaluria leads to calcium oxalate crystal formation and subsequent urolithiasis. This study aims to analyse the effect of treatment compliance in hyperoxaluria, firstly by analysis of patients with non-primary hyperoxaluria and secondly via systematic review in patients with any hyperoxaluria.

Methods: In a retrospective cohort study, adults with non-primary hyperoxaluria managed with dietary counselling in 2013 were enrolled. Twenty-four-hour (24 h) urine collections initially and at 6 months were obtained. Compliance was assessed by self-reported dietary compliance and 24 h urinary volume >2 L. Patients were followed for 24 months. Primary outcomes were urinary oxalate and calcium 24 h load at 6 months, and urolithiasis-related procedural rates at 24 months. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compatible systematic review of compliance among hyperoxaluric patients was performed.

Results: In the cohort study, of 19 eligible patients (4 female) with median age 52 years, 10 (53%) were considered compliant. Compared with the non-compliant group, these patients had significantly increased subsequent 24 h urinary volume (2250 mL 1600 mL;  = 0.008) and lower procedural rates (10% 56%;  = 0.033). Subsequent 24 h urinary oxalate load was non-significantly lower in compliant patients. Systematic review regarding compliance in hyperoxaluric patients revealed five studies. Only one utilised dietary counselling or analysed compliant non-compliant patients, finding no difference. None examined the effect of compliance on procedural rates.

Conclusion: Hyperoxaluria is an important cause of recurrent urolithiasis. Increasing fluid intake and reducing dietary oxalate reduce the risk of operative intervention and remain fundamental to the treatment of hyperoxaluria.