Colorectal surgery is highly associated with septic complications, therefore, multiple approaches have been used to reduce this complications, one of the most used is mechanical bowel preparation. Lately multiple studies have suggested that mechanical bowel preparation might not be necessary.

Objective: Compare elective colorectal anastomosis with or without mechanical bowel preparation on outcomes, particularly anastomotic leak, surgical site infection, and ileum.

Materials and methods: A clinical trial was conducted including patients with colorectal pathology who underwent elective colorectal anastomosis. Patients were randomized into two groups; with mechanical bowel preparation (Group 1), and without mechanical bowel preparation (Group 2). Surgical, and non-surgical outcomes were evaluated, including anastomotic leak, surgical site infection, ileum, acute kidney injury, pneumonia, and mortality.

The statistical analysis was performed according to the nature of variables, for continuous data using measures of central tendency and dispersion and for the qualitative data with frequencies and percentages. Inferential analysis with student's t-test, and/or Mann-Whitney's U test; chi-square distribution, and/or Fisher's exact test respectively.

Inclusion Criteria:

• Entitlement to the Mexican Institute of Social Security
• Signed informed consent
• Patients with colorectal pathology who needed primary elective colorectal anastomosis
• Body mass index >18, and < 31

Exclusion Criteria:

• Patients who dropped out from the study or withdrew the informed consent
• Patients who did not accepted the surgical procedure
• Patients who had been submitted to surgery before entering the protocol
• Patients who need a colostomy