Radiofrequency ablation is a newly developed minimally invasive way to treat tumors. From March 2008 to September 2009, we performed B-ultrasound-guided percutaneous radiofrequency ablation on 19 patients with renal tumors located in the dorsolateral aspect of the kidney and the middle and lower pole of the kidney, and the postoperative results were satisfactory. I. General information Among the 19 patients, 12 were male and 7 were female; 11 were left kidney and 8 were right kidney; age ranged from 45 to 78 years old. 17 cases had no obvious clinical symptoms and were admitted to the hospital for the detection of kidney tumor by ultrasound during physical examination. 1 case was a recurrence of right kidney tumor after radical resection of left kidney for VHL syndrome and partial resection of right kidney tumor. 1 case was found to have kidney cancer during preoperative examination for rectal cancer, and percutaneous radiofrequency and rectal cancer surgery were performed simultaneously. The tumor diameter of 19 patients ranged from 2.2 to 4.3 cm, with a mean of 2.35 cm. 15 patients underwent one cycle of radiofrequency and 4 patients underwent two cycles of radiofrequency. Single needle was performed in 15 cases and double needle in 4 cases. The procedure was performed under general anesthesia or epidural anesthesia, in prone position, with real-time ultrasound guidance to insert the radiofrequency needle and penetrate the electrode into the tumor tissue. Turn on the cold circulation pump and radiofrequency generator sequentially. The cold circulation pump continuously pumps ice water into the built-in tube of the electrode to keep the needle tip temperature at 16℃～20℃. One cycle of radiofrequency ablation (12 min) is performed, and the tissue temperature rises above 60 ℃ at the end of the treatment, which can ensure the killing of tumor cells, and the radiofrequency time is 12-30 min. The coagulation foci of single needle electrode can reach 3 cm, and the cluster electrode can produce spherical coagulation foci of about 6 cm. Multi-point and multiple ablation can be performed if necessary. Before the end of RF, the output power is adjusted to keep the needle tip temperature at 90-100 ℃ for 10s, so as to carbonize the needle tract and stop the bleeding, and also to prevent the needle tract transfer. The Tru-Core18G biopsy needle was routinely used to perform two to three needle puncture biopsies of the tumor under ultrasound guidance and sent for pathological examination. Results All 19 procedures were successful, with an operative time of 30-50 min, averaging 37 min, without intraoperative bleeding or complications such as perirenal bleeding, perirenal effusion, or adjacent organ damage. Postoperative hospitalization ranged from 2 to 5 d, with an average of 2.5 d. One patient had bleeding carnivorous hematuria, and seven patients had more obvious pain in the renal area, which was relieved after symptomatic treatment. Postoperative pathology: 14 cases of renal cell carcinoma, 3 cases of renal malformation tumor, 2 cases of pathology could not be diagnosed. 1 case of postoperative review confirmed residual tumor, and percutaneous radiofrequency treatment was performed again. The follow-up period ranged from 5 to 19 months, with an average of 12 months, and no local recurrence or distant metastasis of the tumor was detected. The postoperative follow-up CT scan showed a slightly dense shadow of the original tumor in the kidney with no significant enhancement after enhancement, and ultrasonography did not show any contrast agent entering the lesion. (See the attached Figures 1-4) Discussion Radiofrequency ablation, cryoablation, microwave ablation, and high-energy focused ultrasound are several modalities of local minimally invasive tumor treatment developed in recent years, which have been gradually carried out in some foreign medical centers. Radiofrequency ablation is recommended as an alternative local minimally invasive treatment for tumors in foreign treatment guidelines [1]. This technique refers to the use of single-needle or cluster electrodes, guided by ultrasound, CT, MRI, open surgery or laparoscopy, to insert radiofrequency electrodes into tumor tissues for radiofrequency treatment, which dehydrates and dries the tumor tissues around the electrodes and then produces coagulative necrosis to inactivate the tumor tissues. The local tissues show coagulative necrosis after radiofrequency, and thermal injury leads to acute necrosis of cell organelles, but the morphology of cells does not change. The tumor organelle protein denaturation necrosis inactivation after radiofrequency, cell staining can be found to show necrosis of the organelle, but the structure and morphology of the cells did not change in a short time [2]. Therefore, pathological sections of tumors resected after radiofrequency still showed renal clear cell carcinoma, which indicates that taking biopsies after radiofrequency does not affect the determination of pathological results and can eliminate the occurrence of needle tract implantation [3]. After radiofrequency, the tumor shrinks gradually with the absorption of local tissues, and the maximum diameter of the tumor remains basically the same after about six months on CT, and the possibility of recurrence should be considered if the tumor increases significantly. We were the first to carry out laparoscopic radiofrequency ablation of renal cancer in China [4], and on this basis, we adopted percutaneous radiofrequency for such tumors that can be easily localized and punctured by percutaneous ultrasound. Ultrasound is one of the most widely used, economical, non-invasive and convenient examination devices in clinical practice, although it is not as intuitive and accurate in localization as CT or MRI. However, today’s ultrasound equipment has high resolution, is small and easy to move, can be brought into the operating room, and has a variety of different ultrasound probes to accommodate a variety of procedures. For tumors in the mid and lower dorsal pole of the kidney, ultrasound can accurately localize, guide radiofrequency and biopsy. Current reports in the literature also suggest that tumors smaller than 4 cm are more suitable for radiofrequency treatment [1]. We experience that tumors smaller than 4 cm, which can be destroyed frequently in one shot cycle and do not need to re-enter RF, are more suitable for ultrasound-guided RF ablation. Because the size and shape of the tumor has changed after the first RF cycle, which makes it difficult to determine the depth and scope of the second RF needle entry and may cause omission, therefore, it is not recommended to use percutaneous ultrasound guidance for larger tumors that require 2 or 3 RF cycles. As with partial nephrectomy, RF ablation also sets the extent of destruction to 0.5-1.0 cm beyond the tumor perimeter, which requires the formulation of the angle and depth of needle entry under ultrasound guidance, and there is a certain lack of 2D ultrasound in this regard. ideal RF effect. The size of the tumor is an important factor in predicting whether the tumor can be completely destroyed, with a high rate of complete destruction for tumors less than 3 cm in diameter [6]. The location and growth pattern of the tumor also determine the RF effect of the tumor, with endogenous tumors and tumors near the hilum being relatively less effective [7]. We chose tumors located in the dorsal and lateral parts of the kidney, the middle and lower pole tumors, which are easy to locate under ultrasound, and the exophytic tumors are easy to locate with ideal RF effect. We also tried to localize RF under CT, but the cost of CT is high, not only there is radiological damage to the patient, but also there are limitations of anesthesia, resuscitation and cost to perform the procedure in CT room, so it is difficult to carry out widely. Foreign literature is mostly guided by CT or MRI, which has accurate localization and can be performed immediately after radiofrequency to check the destruction of the tumor with enhanced scanning [6]. We applied ultrasonography to examine the presence or absence of blood flow in the tumor foci after RF, and also to examine the destruction of the tumor. The advantages of ultrasound are: ultrasound equipment is easily portable, can be brought into the operating room, is inexpensive, has no radiological damage, and can be monitored in real time. However, the location of the tumor for which ultrasound is used is special, as it must be close to the body surface and located in the middle and lower pole of the kidney, and must be easily localized by ultrasound. Moreover, ultrasound images are not as intuitive as CT or MRI and require the cooperation of the ultrasonographer, which to some extent may cause differences in the spatial conformation of the tumor and in the understanding of the needle position, angle and depth, which may affect the effect of RF. Ultrasound-guided localization of radiofrequency has special requirements on the location of the tumor. Before radiofrequency, we should do a prone ultrasound examination of the patient together with the ultrasonographer to determine the location, direction and depth of the needle. Percutaneous ultrasound-guided radiofrequency ablation has the advantages of less trauma, faster recovery, shorter postoperative hospital stay and fewer complications. We believe that it is an alternative treatment method for patients whose tumor location is easy to locate by ultrasound guidance, who are in poor physical condition and uncomfortable to operate or unwilling to operate. The results of its treatment are still satisfactory as reported in the literature, but its more long-term efficacy still needs to be observed by further accumulation of cases and long-term follow-up.