Exploring the effect of protective ileostomy compared with transverse colostomy on the occurrence of complications, the occurrence of serious side effects of adjuvant chemotherapy and disease recurrence in patients with low rectal cancer after radical surgery from the perspective of intestinal microecology.

Low rectum refers to the rectal area <7 cm from the anal verge. At present, with the development of modern medical technology and the change of surgical concept, more and more patients can achieve the goal of radical treatment of low rectal cancer while preserving the anus. The occurrence of anastomotic leakage after anus-preserving surgery for low-grade rectal cancer is a more common and serious complication, with an incidence ranging from 2.4% to 15.9%, and the morbidity and mortality rate after anastomotic leakage can be as high as 16%.

A protective stoma protects the anastomosis by temporarily establishing an artificial channel above the anastomosis to divert feces and avoid mechanical pressure and contamination of the anastomosis by intestinal contents, allowing the anastomosis to grow and heal in relatively clean external conditions. The current choices of protective stoma sites are terminal ileum and transverse colon. Analysis of domestic and international studies shows that both protective transverse colostomy and ileostomy can achieve the effect of diversion of stool, but whether there is a difference in preventing anastomotic leakage and reducing adverse outcomes of anastomotic leakage remains to be investigated. There are significant inconsistencies between domestic and international studies regarding the incidence of stoma-related complications caused by different stoma sites: the study by Rondelli et al. showed that terminal ileostomy was associated with lower stoma-related complications, and a domestic meta-analysis recommended terminal ileostomy after radical rectal cancer surgery. In contrast, the study by the team from the Union Hospital showed that transverse colostomy was associated with significantly lower rates of stoma-related complications and perioperative complications of stoma reentry.

In addition, according to the Union Hospital team study, the incidence of postoperative intestinal microbiota dysbiosis was higher in patients who underwent ileostomy compared to those who underwent transverse colostomy. The total intestinal microbiota in the colon accounts for more than 90% of the systemic intestinal microbiota, and the intestinal microbiota in the large intestine can be roughly restored to preoperative levels after transverse colostomy, whereas a large amount of intestinal microbiota is lost and difficult to restore after ileostomy. The dominant flora in the colon, such as Clostridium and Enterococcus, are less likely to colonize the small intestine, which may adversely affect the intestinal and systemic immune regulation and antitumor immune effects of the body. In addition, patients with progressive low-grade rectal cancer routinely require adjuvant chemotherapy after radical surgery, and there are no studies at domestic or abroad on whether terminal ileostomy, which is more common than transverse colostomy for intestinal dysbiosis, has any differences on the efficacy and toxic side effects of adjuvant chemotherapy for patients; furthermore, it is also important to investigate whether the two different stoma methods have an impact on long-term disease recurrence and overall survival of patients. In addition, whether the two different stoma modalities have an effect on long-term disease recurrence and overall survival is also an important research question.

Therefore, the investigators propose to conduct a prospective, randomized, controlled study in patients with low-grade rectal cancer who underwent radical surgery (with or without neoadjuvant radiotherapy) to investigate whether there are differences in the incidence of complications, serious side effects of adjuvant chemotherapy, and disease recurrence after terminal ileostomy versus transverse colostomy from the perspective of intestinal microecology, and to explore the differences in systemic immunity, inflammatory, and metabolic status.

Inclusion Criteria:

1. Pathological confirmed adenocarcinoma of the rectum;
2. Patients age between 18-80;
3. Baseline AJCC stage I-III: cT1-4N0-2M0 (AJCC-8 version);
4. Eastern Cooperative Oncology Group (ECOG) physical status score of 0 to 2;
5. Patients voluntarily sign informed consent.

Exclusion Criteria:

1. Other types of rectal cancer (adenosquamous carcinoma, squamous carcinoma, neuroendocrine tumors, clear cell carcinoma, spindle cell carcinoma, undifferentiated carcinoma);
2. Combination of rectal cancer with multiple carcinomas;
3. Pre-operative presence of acute and chronic infectious diseases or foci of infection;
4. Intraoperative radical surgery was not performed for various reasons；
5. Colostomy was not performed at the same time as the radical rectal cancer surgery;
6. Combined with intestinal obstruction, intestinal perforation, intestinal bleeding, peritonitis, etc. requiring emergency surgery;
7. Metastatic cancer;
8. Serious heart, lung, liver and kidney disease, can not tolerate surgery;
9. Active liver disease or abnormal liver function with ALT, AST and TBIL more than 2 times the upper limit of normal values;
10. Renal impairment with Cr ≥ 2 times the upper limit of normal or BUN ≥ 2 times the upper limit of normal;
11. Blood leukocytes below the lower limit of normal value, or platelets below the lower limit of normal value, or with other blood system diseases;
12. Pregnancy;
13. Mental illness or serious intellectual disability who cannot describe their feelings correctly;
14. Severe coagulation disorder, bleeding tendency;
15. Patients with severe uncontrolled medical disease, recent history of myocardial infarction (within 3 months), uncontrolled severe hypertension and severe diabetes mellitus;
16. Patients need to be on antibiotics/other probiotics for a long time.