If a 10/12Fr access sheath cannot be inserted due to the ureteral narrowing, the following maneuvers of 'sliding techniques' or 'ballon dilatation' can be performed:

(i) we put two hydrophilic terumo guidewires into the ureter and one of them is inserted into the distal tip of the working channel of the flexible ureteroscope. And the flexible ureteroscope is inserted into the renal pelvis through the Terumo guidewire. In this case, you should use a dusting or popcorn technique instead of a basketing technique.

(ii) a ureteral balloon dilatation was performed if the ureter was too narrow for the flexible ureteroscope to be inserted and the stricture segment is not so long;

(iii) a 6-Fr nelaton catheter should be inserted into the bladder through the urethra to prevent bladder filling which might contribute to the compression of ureterovesical junction, increase in the intrarenal pressure, and limit of the motion of flexible ureteroscope.

How can we upgrade our RIRS skill? Is there any learning curve of performing RIRS? [Cho SY et al, PLoS One, 2014]