The impact of the ratio of renal parenchyma to renal volume on stone-free rates after RIRS: a retrospective study

Renal parenchyma thickness and hydronephrosis degree may predict stone-free rate (SFR) after lithotripsy. This study combined these factors and introduced a new index, the ratio of renal parenchymal volume to renal volume (RPRV) to investigate its prediction role of SFR after retrograde intrarenal surgery (RIRS). We collected data from 119 adult patients with upper ureteral or kidney stones who underwent RIRS from March to September 2023. They were divided into stone-free group (n = 85, 71.43%) and residual stone group. Multivariate logistic regression analyzed the relationship between RPRV and SFR. ROC curve analyzed the predictive efficacy of RPRV. Among the 119 patients, there was a difference in RPRV between the two group (P = 0.002). In overall sample, AUC of RPRV for predicting SFR after RIRS is 0.678 (cut-off value: 0.6890, sensitivity: 95.3%; specificity: 41.2%; P = 0.002). In the 2-2.9 cm group multivariate logistic regression analysis is statistically significant (OR 0.847, 95% CI 0.761-0.942, P = 0.002), with an AUC of 0.769 (cut-off value: 0.6887; sensitivity: 97.8%; specificity: 58.8%; P = 0.001). In the 3-4 cm stone group, no significant difference. RPRV is effective in predicting SFR after RIRS and has clinical guiding significance.