Liver is the most frequently involved organ in distant metastasis of colorectal cancer. According to statistics, liver metastasis exists in about 20% of cases at the time of initial diagnosis and 70% at the time of autopsy. However, with the improvement of treatment level in recent years, the survival period of many patients with liver metastases has exceeded 5 years, and the treatment of liver metastases has been adopted in a positive manner, and the main methods adopted are as follows: a. Surgical resection Surgical resection of liver metastases has the possibility of long-term survival, and this view has been supported by many clinical studies. According to the statistics of different authors, the 5-year survival rate of patients with liver metastases from colorectal cancer that can be surgically resected is 22-58%. The indications for surgery are also being relaxed, and the current view is that as long as R0 resection (negative microscopic margins) can be achieved, surgical resection is advocated, and for patients with intrahepatic recurrence after surgery, resection is still advocated as long as the conditions for R0 resection can be achieved, and clinical data also show that a significant proportion of these patients can achieve long-term survival. Because surgery is highly invasive and not conducive to repetition, the treatment of liver metastases that occur repeatedly in multiple batches is greatly limited, and its status has been challenged by non-surgical minimally invasive treatments that are comparable in efficacy to surgery, less invasive, and can be repeated multiple times. II. Non-surgical minimally invasive treatment Non-surgical minimally invasive treatment has now become an important tool for local treatment of tumors with the development of imaging and related technologies. At present, ablation therapy is the most effective treatment for intrahepatic tumors. According to the different treatment media used, ablation is divided into physical ablation (introduction of cold, heat or radiation to necrosis the tumor, represented by argon helium knife, radiofrequency therapy, radioactive particle implantation, etc.) and chemical ablation (local injection of chemical drugs to necrosis the tumor, such as intratumoral chemotherapy drugs, anhydrous ethanol and acetic acid injection, etc.). For liver tumors below 3 cm, the efficacy of radiofrequency and anhydrous ethanol intratumoral injection has been recognized, and for liver tumors below 3 cm, the efficacy of the above two methods is considered equivalent to surgical resection. With the improvement of equipment, the range of action of radiofrequency ablation is getting larger and larger, and some equipment can reach the range of action of 7 cm in diameter in a single treatment, and the treatment of larger tumors is getting better and better. Nowadays, the progress of minimally invasive methods in the treatment of liver tumors makes it not only an alternative to surgical resection, but also a useful supplement to surgery, making up for many shortcomings of surgical treatment. With the elimination of ultrasound-guided blind areas and the resolution of the problem of accurate localization of residual foci after multiple ablations, we have been able to achieve a tumor-free state in the liver at the PET-CT level in the vast majority of patients, and this state can be maintained for a long time through repeated treatments, which is incomparable to surgery. Treatment of unresectable lesions into resectable lesions Unresectable liver metastases can be converted into resectable lesions by two efforts. 1.Reduce the lesion through drug therapy and systemic chemotherapy Because of the low concentration of drugs in the liver, the local control rate of intrahepatic tumor is lower than that of local vascular perfusion, and the more commonly used local drug delivery route is hepatic artery. Interventional techniques, therefore, can significantly increase the local control rate of liver metastases. After drug treatment, surgery or ablation therapy should be arranged to eliminate the lesions in a timely manner before the tumor disappears completely, because data show that 70% of the cases with complete remission due to drug treatment will recur in situ. 2. Portal vein embolism on the affected side, when the tumor is extensive but located in one lobe of the liver, surgery cannot remove the tumor all together, but the whole lobe can be removed, the main obstacle to remove the tumor at this time is that the residual normal liver tissue after surgery is not enough to compensate for normal liver function, portal vein embolism on the affected side can lead to compensatory hyperplasia of liver tissue on the healthy side, when the amount of residual liver reaches 30% of normal liver tissue, it is enough to maintain normal liver function. Generally speaking, this compensatory proliferation process can be completed within 2 to 8 weeks. After complete removal of liver tumor, how to prevent the reoccurrence of liver metastases Currently, it is believed that liver metastasis of colorectal cancer is through portal vein route, therefore, portal vein chemotherapy has an important position in preventing liver metastasis of colorectal cancer, and most data at home and abroad show that the incidence of liver metastasis can be reduced by 50% to 70% through portal vein chemotherapy. At present, the commonly used intubation methods include intubation during surgery, radiological intervention through hepatic vein and ultrasound-guided percutaneous hepatic penetration, the above three methods are the most reliable but more traumatic; the percutaneous hepatic penetration is the least traumatic and most convenient, but the intubation tube is easy to be dislodged.