Objective:To evaluate the effectiveness and safety of flexible ureteroscopy combined holmium laser lithotripsy(f-URS)in the treatment of special renal calculi. Methods:A total of 22 special patients with renal calculi who were treated by f-URS from January 2014 to August 2015 were reviewed

including 2 cases of obesity

1 case of scoliosis

1 case of renal pelvic ectopia

2 cases of incomplete ureteral duplication

5 cases of calyceal diverticulum

10 cases of isolated kidney and 2 cases of horseshoe kidney. Twelve patients were single stone and 10 patients were multiple stones. Average stone size was(1.50±0.82)cm. Ten patients had a urinary leukocyte count of > 500 cells/μL in routine urinalysis and 6 patients had renal insufficiency before f-URS. Results:All stones were detected and smashed successfully in 21 patients but a bit of stones can not be detected in one patient with horseshoe kidney. The average operation number

time and postoperative hospital days were 1.3 times

(66±24)min and(1.73±1.15)days

respectively.One patient had a fever after f-URS and was cured by intravenous antibiotics therapy. Three patients were not stone free and patients with renal insufficiency had renal function improved. Conclusion:f-URS is an effective and safe choice for special renal calculi.