Evaluation of the Performance of Stone Management According to Size-Hardness (SMASH) Score in Preoperative Planning for Retrograde Internal Surgery (RIRS) in the Treatment of Renal Stones

Abstract

Objectives: This study aimed to assess the effectiveness of the SMASH score in selecting candidates for Retrograde Intrarenal Surgery (RIRS).

Methodology: This retrospective study was conducted at the the Pakistan Kidney and Liver Institute and Research Center (PKLI & RC) from September 2019 to September 2024. Patients aged >14 years with renal stones sized 1–2.5 cm, undergoing their first RIRS, were included. Exclusion criteria were infected urine, staghorn stones, stones >2.5 cm, or requiring repeat intervention. The SMASH score, derived from Hounsfield units and stone size, was evaluated for its role in predicting stone clearance. Data collected included demographic, clinical, surgical, and postoperative outcomes. Statistical analysis employed Spearman's correlation and logistic regression.

Results: Among 260 patients (mean age: 44.88 ± 15.25 years), complete stone clearance was achieved in 80.4% of cases, with a higher success rate in patients with SMASH scores < 15 (67.5%, p < 0.001). Postoperative complications were seen in 12.7%, including urosepsis (9.2%) and UTIs (3.1%). Median operative and laser times were 80 minutes and 57.5 minutes, respectively, and correlated positively with SMASH scores (p = 0.194, p = 0.185, p-value < 0.01). Logistic regression identified stone size as a significant predictor of clearance (OR 5.479, p-value < 0.001). Operative time increased with stone size (p-value < 0.001), emphasizing preoperative complexity. The median hospital stay was one day, indicating rapid recovery.