Distinct metabolic characteristics and risk of stone recurrence in patients with multiple stones at the first-time presentation.

OBJECTIVE

To characterize the clinical and metabolic abnormalities of patients presenting with multiple stones and determine their risk of new stone formation.

MATERIALS AND METHODS

This retrospective case-controlled study consisted of 911 patients who had ureter stones for the first time and 107 age- and sex-matched patients without stones. The patients were classified into 2 groups: those with a single ureter stone (n = 690) and those with 1 or more additional stones somewhere in the ureter or kidney (n = 221). All patients underwent 24-hour urinary metabolic evaluation. The 240 patients (26.3%) who were followed for >12 months (median follow-up, 35.0 months) were included in recurrence analyses. Stone recurrence was defined as "new stone formation," namely, the radiographic appearance of stones that had not been present in previous examinations.

RESULTS

The multiple-stone group had significantly lower urinary citrate excretion than the single-stone (P = .011) and control (P = .003) groups. Compared with the single-stone group, it also had a higher incidence of hypocitraturia (P = .011) and stone recurrence (27 of 84 [32.1%] vs 29 of 156 [18.6%] patients; P = .025). Multivariate Cox regression analyses revealed that stone multiplicity (hazard ratio, 2.343; 95% confidence interval, 1.302-4.220; P = .005) was an independent predictor of recurrent stone formation. Kaplan-Meier curves showed identical results.

CONCLUSION

The patients with multiple stones had distinct metabolic characteristics, particularly hypocitraturia and a significantly higher risk of recurrence than patients with 1 stone. Patients with multiple stones, even if it is their first stone episode, should undergo metabolic evaluation and possibly also potassium citrate therapy to prevent future stones.