Do flexible ureteroscopies affect renal function?

Objective: To determine whether flexible ureteroscopies (f-URS) affect renal function by performing dynamic renal scans (DTPA or MAG3) pre- and post-operatively. Patients and methods: Between April 2010 and March 2024, 945 renal units underwent ureterorenoscopy, of which 101 renal units with upper urinary tract stones (UUTS) completed a renal scan, either DTPA or MAG3 pre- and post-f-URS. The cases were divided into three groups: worsened (>10%), improved (>10%), or unaffected (stable) renal function (⩽10% change). Patient demographics, imaging data, stone properties, and treatment outcomes were comprehensively evaluated. The evaluation of postoperative complications was performed using the Clavien-Dindo classification. Results: The mean patient age was 53.4 years. The mean stone size was 11.4 mm. Renal pelvis, upper, and middle calyces, and lower pole stones were found in 12.9% (13), 28.7% (29), and 34.7% (35) of cases, respectively. Single- and second-session SFRs were 95% and 99%, respectively. A third auxiliary procedure was needed in one renal unit (1%). The mean number of procedures per renal unit was 1.06 (107/101). The mean renal function pre and post-operatively was 47.3% and 48%, respectively. The majority of patients (94.1%) had unchanged renal function. However, three female patients (3%) had a decline in differential renal function (>10%) while three patients (two males and one female) (3%) had an improvement (>10%). A re-intervention was necessary in one patient, interestingly not among those with declined renal function. Conclusions: Flexible ureteroscopy due to renal or ureteral stones has minimal to no impact on renal function. Renal scans pre- and post-operatively may be used in potentially high-risk patients.