Abstract: PD21-09
Sources of Funding: None

Introduction

Stone free rate (SFR) determines ureteroscopy (URS) success rates. Inconsistent reporting using X-ray, ultrasound or CT scan contributes to data heterogeneity. A CT scan provides the most accurate assessment of SFR. Low dose CT scan (LDCT) is an attractive follow up imaging option, offering reduced radiation dose while preserving superior stone fragment visualization of a CT scan. We sought to assess SFR at our high volume institution using low dose CT scan (LDCT) to provide the most accurate assessment of contemporary ureterosopy success rates.

Methods

A retrospective review of all patients undergoing flexible URS for renal stones with subsequent LDCT scan within 6 months of operation date. The operation note, CT report and images of every patient were reviewed to determine a "true", zero fragment SFR. A ureteral access sheath was placed and meticulous basketing of all stone fragments rather than dusting were utilized wherever possible. Patients with ureteral calculi alone, without co-existing renal calculi were not included in this study. Patients with true nephrocalcinosis (as determined by visual inspection of papilla at the time of URS) were assigned the "stone free" category.

Results

Flexible URS was performed in 202 renal units of 150 patients with intrarenal calculi from September 2003 to July 2016. 71 out of 150 patients (47%) were male. 140 renal units were completely stone free by LDCT assessment representing a 69% "true" SFR. 62 renal units had residual fragments. The largest fragment size was 1mm in 3% (6/202 renal units), 2-4 mm in 19% (39/202 renal units) and > 4 mm in 8% (17/202 renal units).

Conclusions

True stone free rate in patients undergoing flexible ureteroscopy for renal calculi utilizing active basketing of fragments, as determined by strict low dose CT assessment, is 69%. In patients with residual fragments, the majority are 2-4 mm in size.

Funding

None