Open rectal resection, low anterior with total mesorectal excision (TME)

Median laparotomy, starting at the symphysis up to a few centimeters above the umbilicus. (It is very important to ensure that the skin incision is actually carried down to the symphysis, as otherwise access to the pelvis is significantly impeded). If necessary, some mobilization of the bladder. Insertion of a drape (foil) and a retractor. Intraoperative assessment of findings.

The mobilization of the left flexure is performed alternately from aboral by dissecting the descending colon in an avascular plane in front of the left kidney and from oral by detaching the greater omentum from the colon up to approximately the middle of the transverse colon with opening of the omental bursa. Finally, the connections to the spleen and pancreas are released.

The colon is retracted medially and the lateral adhesions with the peritoneum lateral to the abdominal wall are sharply divided. Care must be taken to ensure that the dissection is not carried too deeply, that is, down to the psoas and behind the kidney, but rather only the mesosigmoid is mobilized. The ureter will then automatically come to lie dorsally and can be identified. Exposure in the sense of a ureterolysis is not required.

Opening of the mesocolon from centrally below the duodeno-jejunal junction (ligament of Treitz). In doing so, the inferior mesenteric vein can be exposed near the lower border of the pancreas and divided between Overholt clamps.

Now, the inferior mesenteric artery is sought by first incising the peritoneum at the base of the mesosigmoid at the transition to the mesorectum at the level of the promontory. In a ventral distance of about 1cm from the aorta and parallel to it, preparation is carried out cranially until the inferior mesenteric artery can be identified. To spare the nerve fibers located in the origin area of the artery, the vessel is divided approximately 1–2cm distal to its origin from the aorta, but proximal to the origin of the left colic artery, including the central lymph nodes.

Tip: The central ligation of the inferior mesenteric artery is not oncologically mandatory in rectal carcinoma. However, compared to a selective ligation of the superior rectal artery while preserving the left colic artery, a tension-free anastomosis can be created more easily, which is why this approach is usually favored despite the potential disadvantages (poorer blood supply, damage to the preaortic nerves).

Note: A primary vessel division is a priori oncologically sensible, but an advantage has not been proven by studies.

From the left lateral side, preparation is now made into the lesser pelvis by transecting the pelvic floor peritoneum at the peritoneal reflection. In doing so, entry is made into the mesorectal plane from dorsal with careful preservation of the nerves in the lesser pelvis. Then, entry is made into the ventral plane between the mesorectum and Denonvilliers' fascia by incising the anterior reflection.

Note: Even here, meticulous attention must be paid to the preservation of the mesorectum.