Changes in renal papillary density after hydration therapy in calcium stone formers

BackgroundPrevious studies have shown that, compared with non-stone formers, stone formers have a higher papillary density measured with computer tomography (CT) scan. The effect of increased hydration on such papillary density in idiopathic calcium stone formers is not known.MethodsPatients with recurrent calcium oxalate stones undergoing endourological procedures for renal stones at our Institution from June 2013 to June 2014 were considered eligible for enrolment. Enrolled patients underwent a baseline unenhanced CT scan before the urological procedure; after endoscopic removal of their stones, the patients were instructed to drink at least 2L/day of a hypotonic, oligomineral water low in sodium and minerals (fixed residue at 180 degrees C<200mg/L) for at least 12months. Finally, the patients underwent a follow-up unenhanced CT scan during hydration regimen.ResultsTwenty-five patients were prospectively enrolled and underwent baseline and follow-up CT scans. At baseline, mean papillary density was 43.26.6 Hounsfield Units (HU) (43.26.7 for the left kidney and 42.8 +/- 7.1 HU for the right kidney). At follow-up and after at least 12months of hydration regimen, mean papillary density was significantly reduced at 35.4 +/- 4.2 HU (35.8 +/- 5.0 for the left kidney and 35.1 +/- 4.2 HU for the right kidney); the mean difference between baseline and follow-up was -7.8 HU (95% confidence interval-10.6 to -5.1 HU, p<0.001).Conclusions: Increased fluid intake in patients with recurrent calcium oxalate stones was associated with a significant reduction in renal papillary density.Trial registration: NCT03343743, 15/11/2017 (Retrospectively registered).