Impact of BMI on stone clearance and surgical outcomes in retrograde intrarenal surgery: A comparative analysis across four BMI categories

Abstract

Objective:

Retrograde Intrarenal Surgery (RIRS) is prevalent in the treatment of renal calculi. The effect of Body Mass Index (BMI) on stone clearance and surgical results has not yet been investigated extensively. This study sought to analyze the effect of BMI on clinical, procedural, and postoperative outcomes of patients undergoing RIRS.

Methods:

This retrospective observational study was performed at the Pakistan Kidney and Liver Institute and Research Center (PKLI & RC), Lahore, between September 2018 and August 2024. Two hundred and sixty adult patients who underwent RIRS for renal stones were classified into four groups based on BMI: normal weight (<25 kg/m²), overweight (25–29.9 kg/m²), obese (30–39.9 kg/m²), and morbidly obese (⩾40 kg/m²). The clinical and operative information was recorded from electronic data. Outcomes assessed included stone clearance, rates of complications, hospital stay, pain scores, and secondary intervention requirement. Statistics used were Chi-square tests, ANOVA/Kruskal–Wallis tests, and binary logistic regression.

Results:

Stone clearance rates varied across BMI groups (p = 0.027), though multivariate analysis showed that BMI was not an independent predictor. Increased BMI was also found to be linked with more residual fragments (p = 0.029), longer hospital stays (p = 0.004), increased pain scores (p = 0.002). These differences, notwithstanding intraoperative safety, were uniform across the groups. Binary logistic regression found that stone burden ⩾20 mm was the only independent predictor of incomplete clearance (OR = 0.165, p < 0.001), whereas BMI was not an independent predictor.

Conclusion:

RIRS is a safe and successful procedure in all BMI groups. Obese and overweight patients can have suboptimal results, especially regarding clearance of stones and postoperative recovery. Burden of stone continues to be the most important predictor of surgical success. The results indicate the necessity of personalized planning and follow-up, particularly in those with high stone burden or higher BMI.