Abstract: To investigate the effectiveness and safety of minimally invasive percutaneous nephroureteroscopic lithotripsy (mPCNL) for the treatment of renal calculi. METHODS: A retrospective analysis of 138 patients treated by minimally invasive percutaneous nephroureteroscopy was performed. RESULTS: All 138 cases were successfully treated with one-stage stone extraction, 69 cases were treated with primary stone extraction, 42 cases were treated with secondary stone extraction, with a complete stone removal rate of 80.4%. 10 patients with residual stones were treated with ESWL, with an average operation time of 130 min, an average intraoperative bleeding of 50 ml, none of them required blood transfusion, and no serious complications occurred. Conclusion: Minimally invasive percutaneous ureteroscopic lithotomy has the advantages of less injury, faster recovery, higher stone removal rate and fewer complications, and is a better method for treating renal stones. 1. Data and methods 1.1 Clinical data 138 cases in this group, 80 men and 58 women, age 19-69 years old, average 41.4 years old. There were 62 cases on the right side, 71 cases on the left side, and 5 cases on both sides; among them, there were 47 cases of single pelvis and calcium stones, 68 cases of multiple stones, 23 cases of renal cast or antler-shaped stones, with a diameter of 1.2~4.6 cm; 11 cases had a previous history of open stone extraction in the affected kidney, and 120 cases had different degrees of hydronephrosis; preoperative ultrasound, KUB+IVP were performed to confirm the diagnosis, 23 cases had renal CT examination, and all cases Preoperative ultrasound and KUB+IVP were performed to confirm the diagnosis, 23 renal CT examinations were performed, and all cases had mid-stage urine culture. 1.2 Instruments and surgical methods WOLF F8/9.8 ureteroscope, Swiss EMS pneumatic ballast lithotripter, Philips C-arm X-ray machine, and German percutaneous renal puncture dilator with F6~F16 specifications were used. After continuous epidural anesthesia, the patient was first placed in the lithotomy position, the F5~6 ureteral catheter was inserted retrogradely into the ureter on the affected side, and the balloon catheter was left in place, and then the patient was placed in the prone position with a small pillow under the abdomen in the kidney area. Under C-arm X-ray surveillance, inject 36% pantopamine from the ureteral catheter to visualize the renal pelvis and calyces, select the pathway to be punctured, and puncture the desired calyces with an 18-gauge needle, generally with the most middle calyces, while the assistant injects water from the ureteral catheter to cause artificial hydronephrosis. The F8/9.8 ureteral rigidoscope is passed into the renal collecting system, and the surgical field is made clear by flushing with a high-pressure perfusion pump, and a percutaneous renal lithotripsy channel is established. The large stones were broken by pneumatic ballistic lithotripsy and flushed out by high pressure pulsed water from the perfusion pump and retrograde catheter, and the larger stones were removed by alligator forceps. After the operation, the F6 double J tube and F16 nephrostomy tube were routinely left in place. If the stones could not be removed at one time, the second extraction was performed after 5 d. After the stones were removed, the nephrostomy tube could be removed in 3-5 d. If there were still residual stones, ESWL treatment was performed as appropriate. 2. Results: All 138 cases were successfully treated with first-stage stone extraction, 69 cases with primary stone extraction and 42 cases with secondary stone extraction, with a complete stone removal rate of 80.4%. 10 cases with residual stones larger than 0.5 cm in diameter were treated with ESWL. The average operation time was 130 min, intraoperative bleeding ranged from 30 to 130 ml, with an average of 50 ml, and one case of delayed bleeding after surgery, with a bleeding volume of about 200 ml, was cured by bed rest, clamping of the nephrostomy tube, anti-infection and other conservative treatments. In 10 cases treated with combined ESWL, the double J-tube was removed three months after surgery, and in the rest of the patients, the double J-tube was removed one month after surgery. Minimally invasive percutaneous ureteroscopy is a new technique developed and improved on the basis of percutaneous nephrological technique [1]. Compared with the traditional percutaneous nephrological technique, its main improvements are: (1) the percutaneous renal channel is minimized, thus reducing the chance of intraoperative bleeding and loss of kidney units, and the stone can be removed in one stage; (2) the ureteroscope can reach most of the renal calyces instead of the nephroscope, which reduces the residual stones; (3) the ureteroscope can reach most of the renal calyces instead of the nephroscope, which reduces the residual stones. (2) the ureteroscope can reach most of the renal calyces instead of the nephroscope, which reduces the residual stones; (3) the use of high-pressure perfusion flushing speeds up the stone extraction. Therefore, minimally invasive percutaneous ureteroscopy has the advantages of less injury, higher stone removal rate, fewer complications, and faster recovery, and has gradually become the main treatment for kidney stones. The complete stone removal rate was 80.4%, and no serious complications such as damage to surrounding organs occurred, with satisfactory results. Compared with traditional percutaneous nephrolithotomy, the intraoperative and postoperative bleeding was significantly reduced. Nevertheless, intraoperative and postoperative bleeding has been one of the most common and serious complications of this procedure, and some patients with severe hemorrhage even need to undergo nephrectomy. According to the literature [6], the main causes of hemorrhage are: (1) injury to the intercostal vessels, renal parenchymal vessels, or hilar vessels during puncture and channel expansion. (2) Lacerations of the renal parenchyma and lacerations of the calvarial neck during lithotripsy and stone extraction lead to hemorrhage. (3) Infection factor is also one of the causes of hemorrhage. Therefore, our group has taken the following preventive measures to address the above-mentioned causes: (1) The skin puncture site should be selected to avoid the intercostal vessels. Usually, the possibility of damaging the intercostal vessels is small at 1 to 2 transverse fingers below the 12th rib margin, and for those who need to puncture through the 10th and 11th intercostal spaces, the entry should be made in the middle of the two adjacent ribs to reduce the chance of damaging the intercostal vessels. (2) The renal puncture point is usually selected from the posterior lateral side of the kidney, and the so-called “non-vascular area” is punctured through the middle or lower calyx after the group away from the renal hilum, and the needle from the center of the calyx along the long axis of the calyx can avoid damage to the arteries and veins adjacent to the calyx and reduce bleeding [7], and the renal parenchyma and calyx must be punctured into the renal pelvis, and the renal pelvis cannot be punctured directly. In China, Li Xun et al. used a minimally invasive percutaneous ureteroscopic stone extraction via the posterior middle group calyx pathway to treat 152 cases of complicated renal stones. None of the cases had hemorrhage [8], and the majority of this group were punctured through the posterior middle group of calyces. (3) Before expanding the middle channel should be carefully checked whether the working sheath is intact, ugras et al. reported a case of serious hemorrhage due to injury to the kidney caused by rupture of the working sheath [9]; if bleeding is encountered during expansion, the expansion tube can be left to stop bleeding by compression for 10-20 min, and then expanded again, three cases in this group did not continue to bleed after this treatment. (4) The principle of “gradual, shallow rather than deep” should be followed when dilating the channel, generally starting from F6 and increasing with F2 to F16, confirming the position of the dilator under fluoroscopy and marking the depth of dilator entry, keeping the guidewire under certain tension, rotating the fascial dilator back and forth plus advancing the method gradually deeper, dilating The depth of the dilator can be controlled with the help of X-ray fluoroscopy so as not to cause injury to the contralateral renal parenchymal vessels or the hilar vessels. When the ureteroscope is placed for observation, if the dilating sheath does not enter the renal calyces, the ureteroscope can be inserted into the renal calyces along the guidewire under direct vision and then the dilating sheath can be pushed into the renal calyces. (5) During lithotripsy and lithotripsy, high pressure perfusion and high pressure pulse water from the retrograde catheter were used to keep the visual field clear and avoid bleeding caused by blind clamping; high pressure pulse water can flush out a large number of lithotripsy and avoid tearing of the calyx neck and renal parenchyma due to frequent entry and exit of instruments; the operation should be gentle to avoid bleeding caused by excessive swinging of the calyx neck, especially for patients with previous history of open surgery, because the kidney is In particular, in patients with previous history of open surgery, due to the fixed kidney and small mobility, the above situation is more prone to bleeding of the calyx neck laceration; for small calyx stones that cannot be retrieved due to the angle, a change of position can be used to make the stone drain into the renal pelvis and then retrieve the stone; in cases where the stone remains after the second retrieval, more punctures or more times of stone retrieval are not forced, but combined with ESWL treatment [10]. In our group, 10 patients with residual stones were treated with combined ESWL, and 7 of them had their stones removed, which not only reduced the chance of major bleeding, but also decreased the rate of residual stones. (6) If there is bleeding during lithotripsy and stone extraction, the irrigation solution can be changed to ice saline for a period of time with continuous flushing, the bleeding or small bleeding can be stopped, if it is not effective, the operation is suspended and the dilator core is inserted into the sheath, and then observed after 10 min to see if the bleeding continues, venous bleeding can mostly be stopped by this treatment, 6 cases in our group were treated by the above method and the bleeding was stopped and the operation was successfully completed. (7) For the infection factor, all patients in this group routinely performed preoperative middle urine culture, such as positive results, according to the drug allergy to give anti-infection treatment, such as negative results, three days before surgery also routinely use antibiotics, because the infected stone middle urine bacterial culture positive rate is only 24.2%, the operation time more than 2h, intraoperative antibiotics once more, postoperative intravenous drug anti-infection treatment. None of the 138 cases in this group had intraoperative hemorrhage, and one case of late postoperative hemorrhage was cured by conservative treatment, none of which was treated with blood transfusion, and none of which was treated with nephrectomy or super-selective renal artery embolization. We believe that the incidence of hemorrhage can be effectively reduced by taking targeted preventive measures. In conclusion, we believe that minimally invasive percutaneous ureteroscopic stone extraction has the advantages of less injury, faster recovery, higher stone removal rate and fewer complications, and is a better method for treating renal stones, which is worthy of clinical promotion and application.