Prospective comparative study of ultramini percutaneous nephrolithotomy and retrograde intrarenal surgery in treatment of moderate-sized renal lower caliceal calculi

Objective To compare the effectiveness and safety of ultramini percutaneous nephrolithotomy (UMP) and retrograde intrarenal surgery (RIRS) in treatment of moderate-sized (about 1-2 cm) renal lower caliceal calculi. Methods From March 2015 to December 2016, patients in our hospital scheduled for surgery due to renal lower caliceal calculi with the greatest diameter of 10-22 mm were prospectively analyzed. Patients were randomized into two groups according to the random number table. Group UMP's operational channel was only F14 and the nephroscope's diameter was 1 mm. 200 μm holmium laser lithotripsy was used to break the stones which was rushed out by eddy cuurent. In Group RIRS, all patients needed placing a F6 double J stent preoperatively for two weeks.A flexible ureteroscope sheath required imbedding intraoperatively.The stones were smashed by 200 μm holmium laser lithotripsy through the WOLF flexible ureteroscope.The intraoperative and postoperative datas including stone-free status and the complications were compared. Results 100 patients were enrolled in the study 50 patients in Group UMP, 28 were male and 22 were female, mean age was 43.4±7.9 years old.Mean stone size was 14.5±3.0 mm(range 10-22 mm). Among them, 18 cases were complicated with mild and moderate hydronephrosis. The other 50 cases were allocated to Group RIRS, including 31 males and 19 females.Their mean age was 44.5±8.3 years old and mean stone size was 13.7±3.1mm (range 10-21 mm). Among them, 16 cases were complicated with mild and moderate hydronephrosis.No statistically significant difference were seen between the two groups(P>0.05). After three months’ follow-up, one-time stone free rate(SFR) of UMP group was 94.0%(47/50), which was significantly more superior than the 72.0%(36/50) of the RIRS group(P 0.05). Conclusions Both UMP and RIRS procedures are effective and safe in the treatment of moderate-sized renal lower caliceal calculi. Compared with RIRS, UMP may be more effective and has less operating time, however wtih more intraoperative blood loss. Key words: Renal lower caliceal calculi; Ultra-mini percutaneous nephrolithotomy; Flexible ureterorenoscope; Holmium laser; Prospective study