Objective To investigate the indications, methods and efficacy of minimally invasive percutaneous nephrolithotomy (Mini-PCNL) for the treatment of complicated upper urinary tract stones. Methods: Ureteroscopy and pneumatic ballast lithotripter were used for lithotripsy after minimally invasive percutaneous nephropuncture under X-ray positioning. Results Among the 68 patients, 25 patients had one stone removal, 35 patients had second-stage percutaneous nephrolithotomy, and 5 patients had third-stage percutaneous nephrolithotomy. 12 patients were treated with ESWL after the operation, and the stone removal rate was 95.6%. Conclusion Mini-PCNL has the advantages of high success rate of stone extraction, small trauma, quick recovery and short hospital stay in the treatment of complicated upper urinary tract stones. [Keywords] Minimally invasive percutaneous nephrolithotomy; ureteroscopy; upper urinary tract stones Upper urinary tract stones include calyces, pelvic and upper ureteral stones, which are traditionally treated by extracorporeal shock wave lithotripsy (ESWL) and open surgery. With the further development of urological endoluminal surgery, minimally invasive treatment is gradually becoming one of the main treatment methods for upper urinary tract stones, especially for complex upper urinary tract stones, such as renal antler-shaped, cast stones, kidney stones combined with ipsilateral ureteral stones, etc. From September 2004 to May 2006, we used minimally invasive percutaneous nephrolithotomy (Mini-PCNL) to treat complicated upper urinary tract stones, and achieved better efficacy, which is reported as follows: Subjects and methods 1. Subjects There were 68 cases in this group, 31 males and 37 females, aged 26-71 years, with an average age of 46 years. Among them, there were 11 cases of solitary renal pelvis and calcium stones, 48 cases of renal deerstalker or cast stones, and 9 cases of renal stones with ipsilateral ureteral stones. The maximum diameter of upper ureteral stones was 3.0 cm, and the maximum diameter of renal stones was 10 cm. 16 of them had undergone ESWL or open surgery to treat the stones, which were not crushed or still had large fragments of stones remaining and were difficult to be discharged. Preoperative ultrasound and IVP examinations were performed to determine the location and size of the stones. For patients with a history of open surgery or repeated ESWL treatment, preoperative CT examination of the kidney is routinely performed to understand whether there are changes in the kidney structure. 2.Surgical method Two-point combined anesthesia in the spine is used, i.e. continuous epidural anesthesia in the upper point and lumbar anesthesia in the lower point. The patient was first placed in a lithotomy position, retrograde insertion of the F5-6 ureteral catheter to the renal pelvis followed by indwelling catheterization, then prone position with padding of the abdomen in the renal area (about 10-15 cm high) or adjustment of the surgical bed to make the lumbar region into a low arch, so that the affected side of the waist is bent and the rib gap is widened. According to the specific situation of the stone, the choice of gap and puncture point is decided, often from the lower edge of the 12th rib and the intersection of the posterior line of the internal organs as the puncture point, according to the actual situation can make appropriate changes, usually the direction of puncture to the patient in the front and above the oblique needle, with the horizontal line into 30o ~ 60o, with the body longitudinal axis into 50o ~ 80o, penetrating the kidney peritoneum after the visible needle tail swing with breathing, larger hydronephrosis penetration into the collection system has obvious The feeling of breakthrough is not obvious after the kidney without hydronephrosis or open surgery, and the retrograde injection of water through the ureteral catheter is conducive to successful puncture, which can be determined when the needle core is removed after penetrating the renal collection system and urine drips out. Intraoperatively, a C-arm X-ray machine is used for positioning. When it is determined that the puncture needle has entered the renal calyces or pelvis, a 0.965 mm zebra guidewire is placed, preferably inserted into the ureteral lumen, which should be more than 5 cm if it is coiled in the kidney, and after withdrawing the needle sheath, the skin and fascia are punctured along the guidewire with a small sharp knife. The fascial dilator is placed over the guidewire, and the channel is expanded toward the kidney. The same surgeon operates, straightening the guidewire slightly backward with one hand, rotating the dilator with the other hand and advancing it forward, gradually expanding it from F8 to 16, keeping the amplitude of each push equal to avoid bending the guidewire or pushing it too deep to penetrate the renal pelvis, with intermittent X-ray fluoroscopic observation of the process. After finding the stone, the stone is crushed by EMS pneumatic ballistic lithotripter. Small stones can be flushed out by hydraulic perfusion pump and slightly larger stones can be removed by ejaculator. After surgery, the ureteral double “J” tube and F16 nephrostomy tube were routinely placed, and the nephrostomy tube was clamped for 2 hours to prevent bleeding. In this group of 68 cases, all the PCN channels were successfully established in phase I. Two of them were transfused because of more bleeding. The residual stones after the first stage lithotripsy could be retrieved in the second stage or extracorporeal shock wave lithotripsy. There were 25 cases of one-time stone extraction, 35 cases of secondary stone extraction, 5 cases of tertiary stone extraction, 3 cases of stone residue, 53 cases of complete stone removal, 12 cases of small residual stones supplemented with ESWL treatment, stone removal rate of 95.6%. There were no complications such as ureteral perforation and postoperative urinary fistula in this group, and all patients were discharged from the hospital cured. The nephrostomy tube was removed 3-5 days after surgery, and the double “J” tube left in place was removed 2-4 weeks after surgery. Discussion Upper urinary tract stones can cause obstruction and cause hydronephrosis in patients, impairing renal function. ESWL saves the patient from incision, but is often limited in the treatment of stones >2.5 cm in diameter, cystine stones, and urinary tract obstruction below the stone; transurethral ureteroscopy is more effective in lower and middle ureteral stones, but the upper ureter is difficult to reach or remove. urinary tract is difficult to reach or remove stones; open surgery is largely not used in hospitals that are equipped to perform endoluminal surgery because of its disadvantages such as high trauma, slow recovery and long hospital stay. Traditional PCN is not accepted by urologists because of its thick percutaneous renal channel, which is prone to intraoperative and postoperative renal bleeding, postoperative leakage, perirenal hematoma and large postoperative renal parenchymal scar, and more tedious operation, and its application in endoluminal urology is very narrow. In recent years, domestic and foreign scholars have proposed the idea of minimally invasive PCN, which requires a significantly smaller channel for expansion than conventional nephrostomy and basically solves the two most important problems of injury and bleeding. The key to the success of this procedure is the selection of the puncture site, and the insertion of a ureteral catheter and water injection before puncture to create an artificial “hydronephrosis” is also very important for the success of kidney puncture. The design of the puncture site should focus on the proximity to the kidney and the proximity to the stone, and the shortest distance to the kidney and the stone should be chosen as the puncture expansion path. Usually, the closest point to the stone is chosen as the puncture point under X-ray guidance in the area between the 11th intercostal space or the posterior axillary line of the 12th rib and the scapular line, and the entry is made from the posterior row of the middle renal calyces, which can reduce bleeding caused by puncture expansion and facilitate the ureteroscope to swing from the middle to the upper and lower renal calyces and the distal ureter. During the operation, the puncture should be accurately positioned, and the needle should be inserted and dilated rather shallowly than deeply, and as far as possible from the dorsal side of the posterior axillary line, in order to avoid injury to the abdominal organs, and when puncturing the middle and upper renal calyces, the needle should be inserted quickly at the end of expiration to reduce the chance of pleural injury. This method has the following advantages: (1) Small trauma to the skin, subcutaneous fat, muscle and perirenal tissues, and rapid postoperative recovery of the patient. (2) Operated under direct vision, the stone is broken directly and can be removed repeatedly through the working channel to remove the stone. (3) Even if the stone enters the renal calyces, the stone can be removed by adjusting the angle of ureteroscope, which is difficult to achieve in open surgery. (4) Less damage to the renal system, although it causes damage to the kidney, the scope of damage is greatly reduced compared with open surgery. (5) It is used for embedded stones that failed to be treated by other methods, hard cystine stones and ammonium oxalate stones, distal ureteral stenosis combined with stones, stones after urinary flow diversion, etc. In the process of lithotripsy, the pelvis or ureteral obstruction is lifted first, and the zebra guidewire is passed through the stone, which can prevent the stone or blood clot from blocking the ureter. If the stone is too large, it is difficult to remove the stone at one time or there is much bleeding during the operation, a nephrostomy tube can be left in place, and the stone will be removed in 5-7 days in the second stage or even in the third stage. Minimally invasive percutaneous nephrolithotomy is easily accepted by patients because of the small trauma and good stone fragmentation effect.