Retrograde Intrarenal Surgery Versus Mini-Percutaneous Nephrolithotomy for Treatment of Medium Size Pediatric Renal Stones (10-20millimeters). A Randomized Controlled Trial

Pediatric urolithiasis has become a major health problem, especially in the developing countries. It is a well-known risk factor for renal impairment and end-stage kidney disease (ESKD). Also, it's associated with a bad quality of life (Qol) for both parents and child. Children represent 2-3% of the total population of stone-formers. Similar to adult urolithiasis, the prevalence of pediatric stones is widely variable in different parts of the world. it changes with sex, race, geographical and climatic factors.

Renal stones in pediatric patients are usually caused by an underlying disorder, such as anatomical and metabolic anomalies or recurrent urinary tract infections, So, children with renal stones are at higher risk for recurrence and multiple interventions on the kidney Over the last decades, the management of pediatric urolithiasis had been replaced by less invasive endourological procedures and the role of open surgeries had been greatly subsided. According to the last guidelines from the European Association of Urology (EAU) and the American urological association (AUA), the standard treatment of renal stones between1-2 cm is shockwave lithotripsy (SWL), percutaneous nephrolithotomy (PNL) and retrograde intrarenal surgery (RIRS). However, the first choice between these modalities is still controversial until now.

SWL is one of the most effective treatment options for pediatric stones, however, its long-term effect on developing kidneys is not clear yet. Also, its efficacy decreases significantly with increasing stone size and multiplicity. The requirement for multiple sessions and the need for general anesthesia in children are other drawbacks of this procedure.

PNL has significantly higher stone-free rates (SFR) and lower requirements for auxiliary procedures compared with SWL. This trend is further promoted by the introduction of miniaturized PNL (mini-perc), which is postulated to be less invasive compared with standard PNL because of the miniaturized instruments. However, PNL may present problems in children, despite modifications, such as the "mini-perc," because of the small size and mobility of the pediatric kidney, friable renal parenchyma, and the small size of the collecting system.

On the other hand, the quality of flexible ureteroscopy and endoscopic instruments showed an outstanding development over the last years which made RIRS a feasible option for pediatric renal stones. Experience suggests that flexible ureteroscopy has a lower risk of kidney damage and bleeding. However, the disadvantage of RIRS in children includes the need toindwell double-J stent in advance, the risk of ureteral injury, and the high cost of equipment purchase and maintenance, which may limit the application of RIRS in children with upper urinary tract calculi.