This study focused on the alterations of gut microbiome and function during defunctioning ileostomy, and observed the effects of probiotic intervention on intestinal microbiome and function. The investigators looked forward to find the specific intestinal maladjusted flora from this work, which could provide a new scheme for the subsequent treatment of the damaged intestinal function and the reduction of the incidence of postoperative complication.

Inclusion Criteria:

1. Patients with primary rectal cancer received total mesolectal resection combined with defunctioning ileostomy.
2. Patients voluntarily sign informed consent.

Exclusion Criteria:

1. Disease progression or death after surgery.
2. Patients with inflammatory bowl disease.
3. Patients need to be on antibiotics/other probiotics for a long time.