The liver receives dual blood supply from portal vein and hepatic artery, and the contouring rate of blood reaches 1800 ml/min. Portal blood from the digestive tract accounts for about 70%~80% of liver blood supply. The liver is the best environment for the growth of metastatic cancer because of its rich blood flow, high sugar and low oxygen content, and nutrient-rich filtrate in the Diaphragm, especially colorectal and gastric malignant tumors are very prone to liver metastasis, and the diagnosis and treatment of liver metastasis of colorectal cancer and gastric cancer will be discussed below. Colorectal cancer is a malignant tumor with a high incidence rate, accounting for the second highest incidence rate of malignant tumors in developed countries in Europe and the United States, and the trend is increasing in China. Liver is the most common metastatic site of colorectal cancer. In the autopsy of patients who died of colorectal cancer, the rate of liver metastasis is as high as 60-71%, and liver metastasis has occurred in 20-40% of patients when colorectal cancer is diagnosed. The incidence of heterochronous liver metastases after treatment of the primary site is as high as 50%. The prognosis of patients with liver metastases from colorectal cancer is poor, and the survival time varies according to the time of detection and treatment. Bengtsson reported a median survival of 4.5 months and a three-year survival rate of 0. Expected factors of liver metastasis from colorectal cancer: If the possibility of liver metastasis can be predicted at the time of resection of the primary site of colorectal cancer, and the high-risk patients can be treated more aggressively and followed up more closely accordingly, it is an important part of preventing liver metastasis. Currently, the expected factors of liver metastasis in colorectal cancer are: (1) preoperative CEA and SLX (Sialyl Le(x)) levels in colorectal cancer, and there are significant differences in the risk of liver metastasis and survival between CEA and SLX positive patients and negative patients; (2) vascular endothelial growth factor (VEGF), and the overexpression of VEGF in colorectal cancer tissues predicts a significantly higher possibility of liver metastasis. Postoperative follow-up of colorectal cancer: Colorectal cancer liver metastasis does not show any symptoms for quite a long period of time, but if weakness, fever, anorexia, weight loss, vague pain in the upper abdomen or palpable mass, jaundice and ascites appear, it already belongs to advanced stage. Therefore, it is crucial to make a timely diagnosis when there are no symptoms. Therefore, some doctors believe that regular follow-up should be carried out systematically after colorectal cancer surgery, including CEA every three months, routine blood tests, liver function, abdominal ultrasound or CT every six months, and colonoscopy or colon gas-barium double imaging once a year. Close follow-up does not prevent metastasis, but it can significantly improve the rate of curative surgical resection and patient survival time after liver metastasis. There are also different opinions on whether CEA can monitor colorectal cancer metastasis and recurrence. some authors believe that the sensitivity of CEA level to diagnose colorectal cancer recurrence is 36%, while the significance of CEA level applied to postoperative diagnosis of liver metastasis is greater, with a sensitivity of 60%, specificity of 94%, positive predictive value of 60% and negative predictive value of 94%. Hohenberger et al. reported that colorectal cancer liver Carriquiry et al. concluded that elevated CEA after radical colorectal cancer surgery is a fairly accurate marker of recurrence, with a sensitivity of 100% and specificity of 98%, especially in liver metastases. While other authors believe that some poorly differentiated tumors do not produce or rarely produce CEA, so a low CEA cannot negate the diagnosis. Therefore, most patients with liver metastases may have abnormally high CEA levels, which can prompt doctors to enhance follow-up of patients with parallel CT or ultrasound examinations, in order to detect liver metastases early and treat them in time. Ultrasound is a widely used method to diagnose liver metastasis of colorectal cancer. The sensitivity of ultrasound can reach 100% for metastases larger than 2 cm, 61% for 1.0-2.0 cm lesions, and only 20% for lesions smaller than 1.0 cm; the sensitivity of CT examination is almost 100% for liver metastases larger than 2 cm, 74% for 1-2 cm lesions, and very low for lesions smaller than 1 cm. The sensitivity of CT was almost 100% for liver metastases larger than 2 cm, 74% for 1~2 cm lesions, and very low for lesions smaller than 1 cm. CT with intra-arterial portography (CTAP) is currently considered the most sensitive method for diagnosing liver metastases, with a sensitivity of 81-94%, but with a false-positive rate of 6-15%. Therefore, improving the sensitivity of adjuvant examination is the key to early detection of liver metastasis, improving the cure rate and prolonging the survival. Clinical staging of colorectal cancer liver metastases: There are many staging methods for colorectal cancer liver metastases, but there is no unified standard yet. pack (1958) divided colorectal cancer liver metastases into three types according to the sequence of liver metastases: ① first metastases: i.e. liver metastases are found first without primary cancer, and such patients often have poor prognosis; ② simultaneous metastases: i.e. liver metastases and primary foci are found at the same time; ③ delayed metastases: i.e. primary foci are found at the same time; ⑤ liver metastases are found at the same time. (3) delayed metastasis: i.e. after surgical resection of the primary foci, liver metastases appeared during post-surgical follow-up. The Japanese Colorectal Cancer Research Society classified liver metastases from colorectal cancer into: H0: no metastases; H1: liver metastases limited to one half of the liver; H2: a few metastases in both halves of the liver; H3: scattered and more metastases in both halves of the liver. The 5-year survival rate of patients with stage I and II could reach 61%. The impact of various stages on prognosis varies, but in general, patients with better general condition, single liver metastasis and smaller nodes have better prognosis. Surgical treatment of colorectal cancer: Although there are many controversies, most authors still prefer surgical resection of colorectal cancer liver metastases to obtain long-term survival and cure. Wilsonn compared 60 patients with surgically resected colorectal metastases with those with proven metastatic cancer but without surgery, and concluded that the two-year survival rate of patients with liver metastases was not closely related to whether they were operated or not, while their five-year survival rate was significantly related to whether they were operated or not. It is almost impossible to achieve five-year survival in patients without surgery. Therefore, to achieve long-term survival, surgery may be a better choice. Although the indications for colorectal cancer liver metastasis surgery are reported differently, in a comprehensive view, the main indications are: (1) the patient is in good general condition, can tolerate surgery, and has sufficient liver reserve; (2) the primary colorectal cancer can be resected radically; (3) liver resection is technically feasible, such as single metastases away from large blood vessels, multiple metastases occurring in one lobe, etc.; (4) there are no extrahepatic, including paravalvular lymph node metastases; (5) the surgeon’s experience and The surgeon’s experience and technique can be competent. Therefore, the patient should be evaluated individually before surgery, and liver function tests, ultrasound, CT or MRI should be performed to understand the location, number, and size of liver metastases and determine whether surgery is possible. It has been reported that the combined use of laparoscopy and laparoscopic ultrasonography before hepatectomy can avoid unnecessary open exploration. Preoperative colonoscopy or barium enema is necessary as long as radical resection is possible and the colorectal recurrent foci found at the same time are not contraindicated for surgery. In contrast, preoperative puncture biopsy of the occupied liver is not necessary, and a negative biopsy does not change the treatment plan. For liver metastases found at the same time as colorectal cancer, it is controversial whether to remove them at the same time or not. In the opinion of the subscribers, as long as (1) the limited single lesion can be removed; (2) there are no complications, blood loss and contamination when the primary lesion is removed; (3) the incision of the operation is suitable for removing liver metastases at the same time; (4) the patient’s condition can be tolerated; (5) the surgeon is competent, the first-stage removal of liver metastases does not increase the operative mortality and complications, and avoids It also avoids the blow of secondary surgery, shortens the hospitalization time and reduces the economic burden. On the other hand, opponents believe that one-stage resection increases the chance of infection and the blow to the patient during surgery, and does not improve the cure rate; on the contrary, the recurrence rate of liver metastases is higher. Therefore, it is wiser to resect liver metastases 4-8 weeks after colorectal cancer resection. The surgical approach for colorectal cancer liver metastases can be wedge, segmental, lobar or hemihepatic resection depending on the location, size and number of metastases. Regardless of the surgical approach, the radical nature of the surgery should be emphasized because the surgeon will only know if the margins are negative after surgery, so to ensure that enough liver is removed, most authors believe that the margins should be 3;1 cm from the tumor margin, and some even believe that they should be 3;2 cm, and Gayowski statistics show that the five-year survival rate for patients with margins of 3;1 cm is 44%.