- Design
- Single-centre randomised trial
- Population
- 56 adults with recurrent idiopathic calcium stones
- Primary outcome
- Urinary supersaturation of calcium oxalate and calcium phosphate at 8 weeks
- Effect
- Calcium oxalate 4.7 vs 5.0 (P = 0.81); calcium phosphate 1.3 vs 1.4 (P = 0.58)
The single-centre URINE trial randomised 56 adults with recurrent idiopathic calcium stones to empiric prevention, with diet and fluid advice plus indapamide and potassium citrate for everyone, or to selective therapy tailored by 24-hour urine testing. It was published in June 2026.
At eight weeks, calcium oxalate supersaturation (4.7 vs 5.0) and calcium phosphate supersaturation (1.3 vs 1.4) did not differ, nor did urine volume, pH or excretion of calcium, oxalate, citrate or uric acid.
This challenges the assumption that 24-hour urine testing is needed before starting prevention in typical recurrent calcium stone formers. Where testing is costly or hard to collect, as it often is in India, an empiric approach may be reasonable.
The trial was small and short and measured urine chemistry, not stone recurrence, so it cannot show that the strategies prevent stones equally.
- For recurrent calcium stones, empiric prevention gave similar urine chemistry to tailored therapy.
- Consider empiric thiazide-type diuretic and citrate where 24-hour testing is impractical.
- Keep 24-hour testing for unusual, frequent or childhood stones.
- Monitor potassium and sodium on indapamide.
Why it matters
Testing before treating may add cost and delay without changing the urine.
Don't overread it
A small, eight-week trial of urine chemistry; it does not show equal stone recurrence.
The statistics, in plain English
No significant difference in a trial of 56 people means large differences are unlikely, but moderate ones could be missed. Supersaturation is a surrogate, not stone recurrence.
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