Association of Metabolic Syndrome Traits and Severity of Kidney Stones: Results from a Nationwide Survey on Urolithiasis in Japan

Background: Although metabolic syndrome and its individual components have been associated with kidney stone disease, whether the clustering of metabolic syndrome traits increases the severity of kidney stone disease has not been examined in a large-scale study.

Study Design: Cross-sectional analysis.

Setting & Participants: Data were obtained from 30,448 patients enrolled in the 6th Nationwide Survey on Urolithiasis in Japan conducted in 2005. Patients with lower urinary tract stones, struvite stones, cystine stones, or hyperparathyroidism and those younger than 15 years were excluded.

Predictor: Number of metabolic syndrome traits (obesity [body mass index ≥25 kg/m(2)], diabetes, hypertension, and dyslipidemia).

Outcomes: Severe form of kidney stone disease, defined as recurrent and/or multiple stones, and abnormalities in urine constituents (hypercalciuria, hyperuricosuria, hyperoxaluria, and hypocitraturia).

Results: 11,555 patients were included in the final analyses. Proportions of patients with recurrent and/or multiple stones were 57.7%, 61.7%, 65.2%, 69.3%, and 73.3% with 0, 1, 2, 3, and 4 metabolic syndrome traits, respectively (P < 0.001). There was a significant and stepwise increase in the odds of recurrent and/or multiple stones after adjustment for age and sex. In patients with 4 metabolic syndrome traits, the odds was 1.8-fold greater compared with patients with 0 traits (OR, 1.78; 95% CI, 1.22-2.66). In addition, the presence of metabolic syndrome traits was associated with significantly increased odds of having hypercalciuria, hyperuricosuria, hyperoxaluria, and hypocitraturia after adjustment for age and sex.

Limitations: Cross-sectional design, absence of dietary data, ill-defined diagnostic criteria for metabolic syndrome traits, and missing data for the majority of participants.

Conclusions: Metabolic syndrome trait clustering is associated with greater severity of kidney stone disease; increased urinary calcium, uric acid, and oxalate excretion; and decreased urinary citrate excretion. These results suggest that kidney stone disease should be regarded as a systemic disorder linked to metabolic syndrome.