Introduction Paediatric urolithiasis has a recurrent nature because it is frequently associated with metabolic or anatomical disorders or infectious conditions. The rising incidence of the disease with its recurrent nature emphasises the need for minimally invasive therapeutic options. In this study, we aimed to evaluate efficacy and factors affecting the success of retrograde intrarenal surgery (RIRS) in children. Materials and Methods Patients who underwent RIRS were evaluated retrospectively. Two different flexible ureteroscopes (F-URS) were used (7.5F F-URS and 7.95F with a 4.9F bullet-shaped tip). Irrespective of size, all residual fragments were considered as failure. Age, stone size, stone localisation, Hounsfield Unit (HU), stone-free rate (SFR) and complications were evaluated. Results Forty-six patients (29 boys and 17 girls) with a median age of 70.5 months (6-214 months) were treated with RIRS between August 2014 and November 2019. The median operative time was 60 minutes (45-120 minutes). The median follow-up was 26 months (3-65 months). Fourteen patients had lower pole and 10 patients had multiple stones. Ureteral access sheath (UAS) was used in 16 (35%) patients. SFR was 61%. The median number of general anaesthesia was 2 (min 1, max 5). Auxiliary semirigid URS, PCNL and repeat RIRS were required in 4, 6 and 5 patients, respectively. Two patients had postoperative febrile urinary tract infection (UTI) as a complication. Age was associated with post-operative febrile UTI. Presence of stones with HU lower than 700, being operated 4.9F F-URS and without UAS were associated with better SFR. Conclusions RIRS is a minimally invasive method with low complication rates in the treatment of childhood stone disease. Higher stone-free rates are obtained in low HU stones and cases in which we used 4.9 F tip F-URS.

Renal artery pseudoaneurysm (RAP) formation following flexible ureterorenoscopy (FURS) with laser lithotripsy is rare. Previous kidney surgery places patients at an increased risk due to potential vascular injury associated with renal intervention. In our case, a 62-year-old man with a single functioning right kidney and a history of right partial nephrectomy presented 10 days following FURS with holmium laser lithotripsy, complaining of gross hematuria. Attempted conservative management failed. Renal arteriography was done, which revealed a RAP that was managed with selective angioembolization. RAP following FURS can be serious if not managed properly. Most cases present with late gross hematuria. RAP can usually be demonstrated on renal arteriography. Selective angioembolization is the definitive treatment.