Evaluation the clinical value of S. O.L.V.E. nephrolithometry scoring system for predicting the stone-free rate of flexible ureteroscopy (2018)

Objective
To establish S. O.L.V.E. nephrolithometry scoring system, and to evaluate value of S. O.L.V.E. scoring system for predicting the stone-free rate (SFR) of flexible ureteroscopy (FURS).


Methods
Five reproducible variables were included in S. O.L.V.E. scoring system, such as stone surface area (S), obstruction (O), length of calyces funnel (L), visible number of calyces (V) and essence of stone (E). Variables were measured based on preoperative non-contrast computed tomography of urography. Clinical data of 392 patients who underwent FURS for upper urinary tract stones in our department from January, 2017 to June, 2018 were retrospectively analyzed. The total study population consisted of 258 male and 134 female patients. The mean age was (49.5±12.6) years old, ranged from 15 to 85 years. There were 292 patients in stone-free group, including 197 male and 95 female patients. The average age was (49.2±12.8) years old. 37 patients had previous history of renal stone surgery. Median body mass index was 24.7 kg/m2( 18.1-29.0 kg/m2) and median value of preoperative serum creatinine was 72.5 μmol/L (48.9-84.8 μmol/L). The number of patients, whose stone located in the left side and right side were 155 and 137, respectively. The number of patients, whose stones located in ureter, renal pelvis, lower calyceal and non-lower calyceal were 19, 16, 87, 170, respectively. There were 100 patients in non-stone free group, 61 men and 39 women. The average age was (50.4±12.0) years old. 15 patients had previous history of renal stone surgery. Median body mass index was 25.0 kg/m2(18.5-28.8 kg/m2) and median value of preoperative serum creatinine was 73.8 μmol/L (46.5-92.5 μmol/L). The number of patients, whose stone located in the left side and right side were 51 and 49, respectively. The number of patients, whose stones located in ureter, renal pelvis, lower calyceal and non-lower calyceal were 7, 4, 27, 62, respectively. The correlation of S. O.L.V.E. scoring system and stone-free rate, postoperative hospital stay, surgical complications, operation time were analyzed. Receiver operating characteristic curves were drawn to detect predictive value of S. O.L.V.E. scoring system for SFR of FURS.


Results
All cases FURS were performed successfully and the SFR was 74.5%(292/392). Among the variables of the S. O.L.V.E. scoring system in the stone-free group and the non-stone free group, item S were (82.6±69.8) mm2 and (172.6±133.7)mm2, respectively. The item L were (12.7±15.8) mm and (23.9±15.3)mm, respectively. The item V were (0.6±0.7) and (1.3±0.8), respectively. The item E were (817.1±285.5) HU and (902.4±256.1) HU, respectively. The difference was statistically significant (P 0.05). The area under receiver operating characteristic curve of S. O.L.V.E. score was 0.782, higher than that of each variable in S. O.L.V.E. scoring system(S, O, L, V, E were 0.738, 0.535, 0.698, 0.735, 0.593, respectively).


Conclusions
The stone surface area, length of calyces funnel, number of involved calyces were significantly correlated with SFR. The S. O.L.V.E. nephrolithometry scoring system can predict SFR after FURS accurately, and provide assistance for making clinical decisions.


Key words: 
Flexible ureteroscopy; Renal calculi; Ureteral calculi; S. O.L.V.E. score; Stone-free rate