Determinants of renal papillary appearance in kidney stone formers: An in-depth examination

Objectives: The aim of this study is to investigate the association between the urinary metabolic milieu and kidney stone recurrence with a validated Materials and methods: We prospectively enrolled 30 stone formers who underwent retrograde intrarenal surgery procedures. Visual inspection of the accessible renal papillae was performed to calculate PPLA score, based on the characterization of ductal plugging, surface pitting, loss of papillary contour and Randall's plaque extension. Stone compositions, 24h urine collections and kidney stone events during follow-up were collected. Relative brushite and uric acid were calculated using EQUIL-2. PPLA score > 3 was defined as high. Results: Median follow-up period was 11 months (5, 34). PPLA score was inversely correlated with BMI (OR 0.59, 95% CI 0.38, 0.91, p = 0.018), type 2 diabetes (OR 0.04, 95% CI 0.003, 0.58, p = 0.018) and history of recurrent kidney stones (OR 0.17, 95% CI 0.04, 0.75, p = 0.019). The associations between PPLA score, diabetes and BMI were not confirmed after excluding patients with uric acid stones. Higher PPLA score was associated with lower odds of new kidney stone events during follow-up (OR 0.15, 95% CI 0.02, 1.00, p = 0.05). No other significant correlations were found. Conclusions: Our results confirm the lack of efficacy of PPLA score in phenotyping patients affected by kidney stone disease or risk of stone recurrence.