Predictive Value of Stone Management According to Size-Hardness (SMASH) Score for Post-Operative Fever after Ureteroscopy

<b><i>Purpose:</i></b> Post-operative fever (POF) is a common infectious complication following ureteroscopy (URS). Early identification of high-risk patients may help reduce morbidity and optimize peri-operative management. This study aimed to evaluate the predictive value of the Stone Management According to Size-Hardness (SMASH) score-a composite index based on stone size and density-for forecasting POF after URS. <b><i>Patients and Methods:</i></b> We retrospectively analyzed 143 patients who underwent semi-rigid and flexible URS for unilateral ureteral stones between January 2023 and January 2025. Demographic, radiological, and operative parameters were recorded, including SMASH score, Hounsfield unit (HU), stone size and location, operative time, and hydronephrosis. POF was defined as a body temperature ≥38.3°C with a positive urine culture. Comparative and receiver operating characteristic curve analyses were performed to assess predictors of POF. <b><i>Results:</i></b> POF occurred in 17 patients (11.9%). The febrile group had significantly higher SMASH scores (median: 8.08 vs. 5.09, p = 0.001), HU values (720 vs. 626, p = 0.006), and longer operative times (41 vs. 34 min, p = 0.001). Proximal stone location was also more common in the febrile group (p = 0.001). No significant differences were observed in age, gender, comorbidities, or hydronephrosis. <b><i>Conclusions:</i></b> Elevated SMASH scores, longer operative time, and proximal stone location were independently associated with POF after URS. The SMASH score may serve as a useful tool for pre-operative risk stratification, allowing for enhanced peri-operative precautions in high-risk patients.