The Value Of Ureter Diameter In Predicting The Success Of Primary Ureteral Access Sheath Insertion During Flexible Ureteroscopy

Objective:To discussion the feasibility of ureteral diameter measured under CT as a predictor of successful implantation of ureteral access sheath during flexible ureteroscopy,and to evaluate its predictive value.Methods:Retrospectively analysis of the clinical data of 70 patients with renal calculi who underwent flexible ureteroscopic lithotripsy in the Department of Urology of the first affiliated Hospital of Nanchang University from January 2021 to April 2021.Among them,20 patients failed to place the sheath due to ureteral stricture that were included in the experimental group,and 50 patients who were successfully inserted into the ureteral access sheath during flexible ureteroscopic surgery were included in the control group.The diameters of the three physiological strictures of the ureter were measured under CT to represent the narrowest diameter of the ureter,in which the proximal ureter diameter was measured at 1-2mm below the ureteropelvic junction,the middle ureter diameter was measured at the iliac vessel level,and the distal ureter diameter was measured at the proximal end of the ureterovesical junction.The general data of the two groups were statistically compared,and the differences of the diameters of the proximal,middle and distal ureters in the two groups were compared.To analyze the correlation between ureter diameter and successful placement of ureteral access sheath during flexible ureteroscopy.The receiver operating characteristic（ROC）curve was drawn,and the area under the curve（AUC）and cut-off value were calculated to evaluate the predictive value of ureteral diameter measured under CT in ureteral access sheath implantation during flexible ureteroscopy.Results:A total of 70 patients were included in this study,and the total success rate of sheath placement was 71.4%（50 inch 70）.In the control group,the diameters of proximal ureter,middle ureter and distal ureter were（4.20±1.10）mm,（3.87±0.82）mm and（4.13±0.59）mm,respectively.In the experimental group,the diameters of proximal ureter,middle ureter and distal ureter were（3.44±0.71）mm,（2.89±0.35）mm and（3.19±0.55）mm,respectively.There were Statistic difference in ureteral diameter between the two groups（P<0.05）.The correlation coefficients between the proximal,middle and lower ureteral ends and successful placement of ureteral access sheath during flexible ureteroscopy wereρ_proximal=0.340,ρ_middle=0.648,ρ_distal=0.596（P<0.05）.Predictive value of proximal ureteral diameter:AUC:0.72,Cut-off value:3.28mm,Youden index:0.35,Specificity:80.0%,Sensitivity:55.0%,Positive predictive value:52.4%,Negative predictive value:81.6%.Predictive value of middle ureteral diameter:AUC:0.91,Cut-off value:3.27mm,Youden index:0.76,Specificity:86.0%,Sensitivity:90.0%,Positive predictive value:95.6%,Negative predictive value:72.0%.Predictive value of distal ureteral diameter:AUC:0.88,Cut-off value:3.67mm,Youden index:0.68,Specificity:78%,Sensitivity:90%,Positive predictive value:95.1%,Negative predictive value:62.7%.Conclusion:Experimental studies have shown that ureteral diameter measured under CT is a reliable index for predicting the successful placement of ureteral access sheath during flexible ureteroscopy,and the prediction of ureteral diameter at the middle end of ureter is the most reliable.The smaller the diameter of the ureter,the lower the success rate of sheath placement during flexible ureteroscopy.Therefore,as a simple and non-invasive method,preoperative CT measurement of ureteral diameter can provide important reference value for preoperative evaluation and formulation of surgical methods of patients with renal calculi,and has certain clinical significance.