Association of Urine Findings with Metabolic Syndrome Traits in a Population of Patients with Known Nephrolithiasis
Carley Mulligan, MSIII, Kevan Sternberg, MD, Desiree De Waal, RD, John Asplin, MD, Peter Callas, PhD, Virginia Hood, MBBS, MPH.
University of Vermont, Larner College of Medicine, Burlington, VT, USA.
INTRODUCTION AND OBJECTIVE: The odds of nephrolithiasis increase with an increasing number of metabolic syndrome (met-s) traits. An inverse relationship between met-s traits and decreasing urine pH and decreasing ammonium/net acid excretion (NH4/NAE) has been observed in non-stone formers. Uric acid stone formers have been shown to have lower urine pH and lower NH4/NAE than BMI matched controls on a similar diet. We evaluated associations of urine factors from 24-hour urine studies and stone composition with the number of met-s traits in a large cohort of stone-forming patients. METHODS: A retrospective review of records of patients >18 years with 24 h urine collections from July 2009 to December 2018 was conducted. Patient factors, laboratory values and associated diagnoses were identified within 6 months of urine collection and stone composition within 1 year. Four groups based on the number (0, 1, 2, > 3) of met-s traits (hypertension, obesity, dyslipidemia, diabetes) were evaluated. Trends across the groups were tested using linear contrasts in analysis of variance for continuous variables and linear terms in logistic regression for categorical variables. RESULTS: 1473 unique patients met inclusion criteria (835 with stone composition). Met-s groups were 0=684, 1=425, 2=211, 3 and 4 =153. There were no differences among the groups for urine volume, calcium, or NH4/eNAE. There was a significant trend (p< 0.001) and decreasing proportion of calcium phosphate stones (p=0.09) and calcium oxalate stones (p=0.01) with an increasing number of met-s traits. CONCLUSIONS: Stone forming patients with met-s have a defined pattern of metabolic and dietary risk factors that contribute to an increased risk of stone formation including higher acid excretion, largely the result of higher protein intake, and lower urine pH. We did not find evidence of reduced NH4 excretion as an explanation for the low urine pH in met-s described in previous studies.
Back to 2021 Abstracts