This study is a randomized, controlled trial comparing the short- and long-term outcomes of left colonic artery or first sigmoid artery preservation for rectal surgery. Eligible patients will be randomized to D3-lymphodissection with preservation of the first sigmoid artery or left colonic artery in a 1:1 ratio according to a computer-generated randomization list created in advance (includes removal of 252, 253 l/u groups, 241 groups of distal sigmoid colon sites when the neoplasm is highly located).

The operation involves removal of the tumor with oncologically adequate clearance, adherence to the principles of operation in embryonic layers.

The criterion for performing D3-lymphodissection is visualization of the site of the inferior mesenteric artery (IMA) branching from the aorta. During the surgical intervention, l/u groups 252 and 253 are elevated along the superior rectus artery, the NBA is skeletonized circularly so that there are no l/u and no visible areas of fatty tissue.

In the group with preservation of the left colonic artery, the NBA is isolated, clipped and crossed immediately after the LCA, and in the group with preservation of the first SA, the NBA is skeletonized to the level of the first sigmoid artery, clipped and crossed immediately after the first sigmoid artery . After the intestinal resection stage, a colorectal anastomosis is formed, information on drain placement.

The primary endpoint is to assess the incidence of IA - communication of the intraluminal compartment of the intestine with the extraluminal compartment, anastomosis leakage in the area of the formed anastomosis - which will be performed at 30 days postoperatively and categorized according to the Clavien-Dindo scale. HA can be diagnosed by MRI, CT with proctography, endoscopic examination, or patient examination (if low anastomoses are formed).

Any adverse event in the postoperative period is also classified according to the Clavien-Dindo scale and recorded in the individual patient's chart.

Each patient will have an individual electronic record (eCRF open clinica.), where individual patient data will be entered and where the data obtained will be stored.

Inclusion Criteria:

1. Signed informed consent form
2. ECOG status is 0-2.
3. Age over 18 years
4. TNM stage according to version VIII T1b-4aN0-2M0 (M1 in case of resectable metastases confirmed by preoperative staging (colonoscopy, chest and abdominal CT).
5. Histologically confirmed adenocarcinoma of the colon, the proximal edge of which is not higher than or equal to 20 cm from the anus
6. Clinical indications for colorectal resection with anastomosis formation

Exclusion Criteria:

1. Medical or psychiatric reasons affecting the patient's decision to participate in the study
2. Pregnancy or breastfeeding
3. Medical conditions contraindicated for surgery
4. Synchronous or metachronous malignancies
5. Acute intestinal obstruction, bleeding or perforation
6. Preplanned obstructive bowel resection