The project has come to an end due to a lack of necessary funding support.

This is a prospect, randomized control trial to evaluate merits between microperc and FURS for lower pole renal stone

To evaluate the merits of Microperc and RIRS for the treatment for lower pole renal stone between 10-20 mm. Investigators will do a multi-centers randomized controlled trial(RCT). A total of 200 (three hundred) patients, aging between 18 and 60 years are being planned to be enrolled into the study; By simple random sampling technique, patients will be prospectively randomized into group A and group B with a 1:1 ratio. Group A will receive the microperc surgery and group B will undergo FURS.

All the patients will be diagnosed definitely before operations with non-contrast CT+IVP or CTU, lower pole Infundibular length, Infundibular width and Lower pole infundibulopelvic angle were recorded. A double J stent will be inserted in two the relevant ureter two weeks before surgery to guarantee the successful of operations. Patience will receive either microperic or FURS respectively, The operation time , hemoglobin change, renal function, post-operation pain, complications and hospital stay will be recorded. Patience will have follow-up visits at one month and three months, CT and KUB will be taken to evaluate the clearance of renal stone.

Surgical technique Microperc surgery: After the satisfaction of anesthesia, Patient is turned into prone position and the desired calyx is punctured by 4.8F microperc under fluoroscopic or sonographic guidance. No tract dilation is needed. A 200um holmium laser fiber will be used to break stone into less than 2mm. Pull out microperc without drainage tube left; RIRS: After the satisfaction of anesthesia, the patient is placed in the lithotomy position, pull out the pre-inserted double J stent, and place guidewire into the renal pelvis. A 12/14 Fr ureteral access sheath (UAS) is advanced into the proximal ureter over the guidewire, and flexible ureteroscope is passed through the UAS. The stones are fragmented smeller than 2mm using a 200um holmium laser fiber. Fragments are removed using a stone basket for stone analysis if necessary, a double J stent is placed at the conclusion of the procedure and removed post-operative 2 weeks.

Data collection Data for the 2 groups-demographic characteristics, hemoglobin(HB) decrease, white blood cell(WBC) increase, postoperative pain, duration of postoperative hospital stay, complications (modified Clavien system), stone clearance (SFR) and the need for auxiliary treatment are compared.

Mean study endpoint: Final SFR (3 months after procedure) Secondary endpoint: Complications, duration of postoperative hospital stay. re-microperc, ureteroscopy and SWL are considered as auxiliary treatments.

The stone size is defined as the maximum diameter as determined by CT scans. Degree of hydronephrosis are assigned as follow: none (no calyx or pelvic dilation), mild (pelvic dilatation alone), moderate (mild calyx dilation), or severe (severe calyx dilation or calyx dilation accompanied by renal parenchyma atrophy).

Definition of operation time:

For microperc: recorded from the time of the first percutaneous renal puncture to pulling out the microperc.

For RIRS: recorded from insertion of an endoscope into the urethra to the completion of stent placement.

Hospital stay are rounded to the nearest whole day and calculated from the day of surgery to the day of discharge.

Postoperative pain (visual analogue scale(VAS), use of analgesics) will be recorded.

The rate of hemoglobin decrease is assessed by comparing the preoperative Hb level with 24-hour postoperative Hb level.

Non-contrast CT and KUB is obtained for all patients at 3 month after the operation to evaluate the final SFR, allowing time for the spontaneous passage of stone fragments.

Stone-free status are defined as either the absence of any residual stone fragments or the presence of clinically insignificant residual stone fragments in the kidney which were defined as ≤4mm, asymptomatic, non-obstructive and non-infectious stone particles.

Complications of all patients are recorded according to modified Clavien classification system.

Inclusion Criteria:

1. 10-20mm lower pole renal stone measured by KUB or CT;
2. Age between 18-60 years, no gender limitation;
3. Participators can understand the research and sign the consent form without mental illness nor language disorder;
4. Low pole renal stone left after lithotripsy;
5. Lower pole infundibulopelvic angle which measured by IVP or CTU will less than 30 degree;
6. Asymptomatic patients with positive urine white blood cells and negative preoperative urine culture should be treated with antibiotics for 3days before operation;
7. Patients with symptoms of urinary infections, positive urine withe blood cells and positive preoperative urine culture should be treated with suitable antibiotics based on the culture sensitivity result for at least 7days before operation.

Exclusion Criteria:

1. Transplant kidney stone;
2. Renal malformations, such as UPJO, medullary sponge kidney, polycystic kidney, horseshoe kidney, etc.;
3. Combine other part of urinary stones need to be handle at the same procedure, for example ureteral stone, renal pelvic stone, middle or upper pole renal stone;
4. Hematological Disease or Coagulation disorders;
5. Withdraw anticoagulant medicine less than two weeks;
6. Fever or urinary infections without treatment according to the inclusion criteria;
7. Sevier renal dysfunction(endogenous creatinine clearance rate≤50ml/min)
8. Middle or severe hydronephrosis(dilatation of the renal pelvis ≥20mm by ultrasound);
9. Women in menstrual period or pregnancy;
10. Patients have severe disease, such as heart disease, lung dysfunction, and multiple organ failure that cannot tolerate anesthesia or operation.