Objective To discuss the outcomes of the clinically insignificant residual fragments after minimally invasive percutaneous nephrolithotomy. Methods 75 patients (11％) with CIRF among 655 who underwent initial MPCNL from January 2008 to December 2010 were diagnosed by CT scan.Clinical data of 68 patients (39 male and 29 female) were analyzed retrospectively.Previous open surgery hadbeen performed in 13 and ESWL in 20 cases.The median residual fragment size was 1.8 mm.The anatomical distribution of CIRF was 9 at upper pole,14 at middle,34 at lower,9 at renal ureteropelvic junction and 2 at upper and lower pole.Stone analysis showed 40 cases of calcium oxalate calculi,15 of calcium oxalate calculi mixed with carbonate calculi,2 calcium oxalate calculi mixed with uric acid,3 calcium oxalate calculi mixed with struuvite stone,3 struuvite stone,2 uric acid stone and 3 carbonate apatite mixed with struvite stone.Mean follow up was 23 months (12-36).Follow-up consisted of physical examination,serum routine,urine routine and CT imaging. Results 14(21％) patients (3 upper pole,1 middle pole,4 lower pole and 6 ureteropelvic junction) had symptomatic episodes,including 9 hematuria,2 renal colic pain,5 lower urinary tract symptoms,12 with size of CIRF ＞ 4 rmm.8 patients required surgical procedures.5 patients (1 middle,2 upper pole and 2 renal pelvis) underwent ESWL.3 patients with ureteral CIRF were performed ureteroscopic lithotripsy.The CIRF were clear after surgeries.4 paticnts with CIRF ＞ 4 mm did not have symptoms.These patients were recommended to conservational treatments.2 patients with ureteral CIRF had renal colic pains.The stones were excluded after spasmolytic analgesic treatments.27％ (3/11)CIRF located in upper pole had symptom,compared with 4％ (1/14) in middle pole,11％ (4/36) in lower pole and 67％ (6/9) in ureteropelvic junction. Conclusions CIRF can be located variously in the kidney and ureter.Most CIRF are calcium oxalate calculi and locate in the lower pole.Patients with the history of previous open surgery or SWL are more likely to get CIRF.Medium-term follow-up of CIRF revealed that CIRF located in the renal ureteropelvis junction are more likely to have clinical symptoms.