The effect of renal localization on the fate of clinically insignificant residual fragments after retrograde intrarenal surgery: A prospective 1-year follow-up study.

Objectives: Even after a successful retrograde intrarenal surgery (RIRS), clinically insignificant residual fragments (CIRF) could not pass from the kidney. We aimed to find out the differences on the fate of CIRF according to being in the lower pole or other renal localizations.

Methods: 81 patients whose stones were fragmented completely by RIRS were subdivided into two groups as group 1 (lower pole with 41 patients) and group 2 (upper pole, midpole, and renal pelvis with 40 patients). Basal characteristics, urine culture, and renal stone screening were evaluated before and 1-year later from the surgery.

Results: While the number of stone-free patients was less and patients with CIRF ≤4 mm was higher in the lower pole stone group 1-year later from the surgery, there was no statistical difference between the two groups (p=0.158, p=0.136). The number of patients whose CIRFs regrew was 46.3% in group 1 and, 52.5% in group 2. A positive correlation was detected between preoperative stone size and first-year maximal residual fragment size in group 1. Linear regression analysis suggested that preoperative stone size is a predictor of the postoperative first-year residual fragment size in group 1.

Conclusions: We observed that almost the half of the CIRFs in all renal localizations regrew and became symptomatic. There is an effect of the stone size on the residual fragment size while performing RIRS for particularly the lower pole renal stones. Patients with CIRF are needed to be followed-up more closely regardless of the renal localization in order to assess the requirement of retreatment.