The human intestine is colonized with a complex microbial community and forms a super organism with the human body. Intestinal microorganisms include more than 1,000 kinds of bacterias, and their flora is very complex and functions are very diverse. The intestinal flora affects the body's nutrition, immunity and metabolism through interaction with the human body and the external environment, and is closely related to multiple systems. When the flora structure and function are changed, it will lead to the occurrence of various diseases or increase the risk of disease. In recent years, the role of intestinal microbes in tumorigenesis and development, as well as the role of diagnosis and treatment have been paid more and more attention. Abnormal intestinal flora can not only promote tumorigenesis, but also affect radiochemotherapy and immunotherapy effects. It is worth noting that the huge impact of the intestinal flora on immunotherapy suggests that immune checkpoint inhibitors can maximize the efficacy by protecting the balance and diversity of the intestinal microecology. Therefore, in this study, quantitative analysis of the diversity and abundance of intestinal, urinary tract flora, and urine components before and after adjuvant chemotherapy in patients with gastric and bowel cancer was performed. The link between treatment efficacy and prognosis.

Inclusion Criteria:

1. Age 18-70 years old, male or female
2. Surgery specimens were clearly diagnosed as gastric cancer and colon cancer by histopathology
3. The operation method is not limited (both laparoscopic surgery and open surgery)
4. After the perioperative period, stop using antibiotics for not less than 2 weeks
5. It is planned to receive a chemotherapy regimen with a combination of platinum and fluorouracil for a period of 21 days (gastric cancer is the SOX or XELOX regimen, and colon cancer is the XELOX or FOLFOX regimen)
6. Blood routine, biochemical and other related laboratory tests showed no obvious abnormalities
7. There are no contraindications for related adjuvant chemotherapy indications.

Exclusion Criteria:

1. Neoadjuvant treatment before gastric and bowel cancer surgery

2. Previous history: He has suffered from intestinal microecology-related diseases such as cirrhosis, ulcerative colitis, Crohn's disease, irritable bowel syndrome, and urinary system diseases

3. Before the perioperative period, because of anastomotic fistula and gastrointestinal perforation, reoperation

4. The following drugs were used within 2 weeks before enrollment:

   1. Various antibiotics, including antifungals (oral and intravenous)
   2. Probiotic preparations, various prebiotic preparations, etc c Glucocorticoids; d Take drugs known to have a significant effect on the intestinal and urethral flora within half a year (such as proton pump inhibitors, purgatives, bismuth, adsorbents, non-steroidal anti-inflammatory drugs, etc.)

5. Other situations that the researcher considers unsuitable to participate in the experiment;