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Low anterior resection of rectal cancer

Medical editor Arild Nesbakken MD
Gastroenterological Surgeon
Oslo University Hospital


Principles for circumferential dissection

The dissection must be performed as a TME (total mesorectal excision) as described by Heald. A sharp, visually controlled, dissection is performed in the plane between the visceral (Told) and parietal mesocolic/mesorectal fascia.

This plane is identified at open operation by primarily freeing the sigmoid from the lateral abdominal wall continuing medially for the whole mesosigmoid till the central part of the posterior abdominal wall. The autonomic nerves and ureter will be left unharmed on the posterior abdominal wall. Continue in the same plane at the pelvic entrance.

Thereafter the dissection is continued medially. Vessels and lymph nodes are divided at the proper level, the bowel is divided and can be pulled forward. Sharp, visually led dissection is continued in the mesorectal (“holy”) plane on the outside of the mesorectal fascia into the pelvis. The plane is usually easy to identify posteriorly and in front – at the back of the vesicles and prostate in men, the vagina in women. The proper plane should first be identified and followed posteriorly far into the pelvis, thereafter briefly at the front. The plane is more difficult to define laterally, especially at 10 and 2 o’clock. The dissection here should only be performed after the initial posterior and anterior dissection. Functionally important autonomic nerves are located just on the outside of the proper plane and will be injured by an improper dissection. Dissection on the inside of the proper plane will increase the risk for local recurrence.

The quality of the resection can be visualized by inspection of the specimen. This should have an intact, even and smooth mesorectal fascia covering the mesorectal fat. In scientific studies it is customary to grade the appearance of the specimen and this also ought to be performed in clinical routine and described in the surgical record:

  • Grade A: Intact mesorectal fascia on the whole specimen
  • Grade B: Cuts in the mesorectal fascia, none onto the outside of the bowel
  • Grade C: Cuts in the mesorectal fascia onto the rectal wall

The quality of the dissection can further be estimated by the integrity of the parietal fascia on the posterior abdominal/ pelvic wall. This should be intact and cover aorta and nerves.

Principles for circumferential dissection when a low anterior resection may be performed while anastomosis is considered too risky.

A standard TME is performed to the pelvic floor. When an anastomosis is no option the alternatives are:

  • Low Hartmann’s procedure. Rectum is divided distally.
  • Intersfincteric amputation.

Standard TME is performed till the anal canal. A minimal skin incision is performed from below followed by an intersfincteric dissection. This way a large defect in the pelvic floor and skin is avoided and there are few healing problems. A short rectal stump, as in the Hartmann’s procedure, is avoided which can give rise to leakage and pelvic infection.

Principles for regional lymph node dissection

  • For cancer in the rectosigmoid flexure the vessels/lymph nodes should be resected as in sigmoid cancer, which means at the origin of the inferior mesenteric artery at the aorta.
  • For cancer in the upper rectum it is probably adequate to resect the inferior mesenteric artery just distal to the origin of the left colic artery with removal of the local lymph nodes. Fat and lymph nodes in the apical station may be removed even if the artery is resected distal to the left colic artery.
  • For cancer in the middle/lower rectum the vessels/lymph nodes are resected just distal to the origin of the left colic artery.

Principles for division of the rectum and mesorectum during low anterior resection.

Orally the bowel is resected between the sigmoid and descending colon. The blood circulation of the oral bowel end must be inspected. If this seems inadequate the resection should be performed more orally. The left flexure must frequently be mobilized to obtain adequate length of the oral bowel to obtain a tension free anastomosis. This can be facilitated by dividing the inferior mesenteric vein just below the pancreas.

Microscopic tumor does not spread more than 1 cm beyond the macroscopic tumor border. In contrast discontinuous tumor spread in the mesorectum can go as far as 5 cm anal to the lower tumor border, even though it rarely is found further than 3 cm. This is the reason for the following procedures:

  • Tumor in the rectosigmoid flexure or upper rectum (above 12 cm): The rectum and mesorectum are divided 5 cm anal to the tumor. Avoid coning from the mesorectal fascia to the bowel (the total mesorectum must be resected in all 5 cm). A small remnant of the mesorectum will then remain. In Norway this is called PME (partial mesorectal excision), but this term is not applied internationally and may be misunderstood.
  • Tumor at level 8(9) -12 cm: Bowel and mesorectum is resected 5 cm below the tumor which means TME for all practical purposes.
  • Tumor at 5 to 8-9 cm, planned low anterior resection: Resect all mesorectum to the pelvic floor. Adequate distance on the bowel wall < 1 cm.

Reconstruction of the bowel tube after low anterior resection for rectal cancer.

Anastomosis is performed between the descending colon/upper sigmoid and the remaining part of the rectum, if necessary down at the dentate line of the anal canal. A staple instrument is customary applied. An anastomosis at the dentate line can be sutured manually from below.

Types of anastomoses:

  • End-end colorectal anastomosis, also called straight anastomosis.
  • Side-end colorectal anastomosis without reservoir.
  • Side-end anastomosis with reservoir and a blind loop around 5 cm long. The functional result of this is somewhat better for the first 1-2 years, but the final result is similar to the straight anastomosis. Some consider there is a slightly lower frequency of leakage after a side-end anastomosis, but this has not been clarified. The latter carries the possibility of leakage from the staplers closing the blind loop.
  • End-end coloanal anastomosis, colon is sutured to the dentate line.

Temporary defunctioning stoma after low anterior resection

When the anastomosis is 6 cm or below from the anal verge is recommended a temporary defunctioning stoma for 2-3 months until healing of the anastomosis. A defunctioning stoma may also be constructed for anastomoses higher than 6 cm in cases with surgical-technical problems or when a leakage is feared for other reasons in.

While it is possible that the frequency of leakage is reduced by a temporary stoma, this will at any rate reduce the consequences of a leakage. The pelvic infection is usually milder and a reoperation is unnecessary after a temporary stoma. The leakage problem can often be solved by the application of an “EndoSponge” in the perirectal cavity.


  • Laparotomy- or laparascopic equipment


Patient preparation:

  • oral bowel emptying.
  • intravenously antibiotic prophylaxis at the latest at the beginning of the anesthesia. It should be considered whether the patients in addition should have oral antibiotics from the day before the surgery.
  • thrombosis prophylaxis with low molecular weight heparin.

During the surgery it is inserted:

  • epidural catheter for pain management.
  • urinary catheter.
  • naso-gastric tube which is removed by the end of the surgery.


Step 1 – Trocar insertion and diagnostic laparoscopy

  • Trochar insertion with visiport just to the right of and at the level of umbilicus. A further 12 mm port in the right fossa, one in the midline about 5 cm above the umbilicus, one 5 mm in the left fossa, and one 12 mm suprapubically. Avoid the inferior epigastric vessels and insertion of the caudal trochars too low on the abdomen which may impede the angulation within the abdominal cavity.
  • Examine the primary tumor for perforation and/or infiltration into adjacent organs. Thereafter the liver and the total abdominal cavity is inspected with regard to metastases, peritoneal carsinomatosis (especially the pelvis and the paracolic gutters) and other pathology.

Step 2 – Release the left transversal colon, left flexure and descending colon

  • The patient in Trendelenburg’s position tilted towards the right. Position the omentum over the liver and put the small bowel package over the midline to the right. If necessary apply an extra trochar suprapubically to expose the Treitz ligament.
  • Open the peritoneum on the posterior abdominal wall medially to the origin of the inferior mesenteric artery after taking down possible adherances at the ligament of Treitz.
  • Continue in the mesocolic plane towards the left flexure and divide the inferior mesenteric vein. Dissect in the mesocolic plane cranially (avoid dissection posterior to the pancreas) and continue anteriorly to the pancreas and into the lesser sac. Be aware that archadic vessels can be located relatively centrally along the colon.
  • Divide adherances along the tail of the pancreas all the way to the lateral abdominal wall. Continue behind the left flexure and descending colon (in front of the pancreas and the left kidney).
  • In front of the colon the gastro-colic ligament is divided just caudally to the gastro-epiploic vessels, divide the splenocolic ligament.
  • Divide the peritoneum laterally to the descending colon along “the white line of Tod”. Carry through till the anterior and dorsal dissections have met and the left flexure and descending colon are completely free.

Step 3 – Central resection of the inferior mesenteric artery.

  • Lift sigmoid and its mesentery anteriorly and to the left and put it on tension.
  • Incise the peritoneum at the pelvic entrance till the origin of the inferior mesenteric artery in the gutter between the posterior abdominal wall and the sigmoid mesentery.
  • Continue in the posterior mesocolic plane behind the sigmoid mesentery towards the lateral abdominal wall (avoid left ureter).

A. Cancer of the upper rectum (>12 cm)

  • Dissect the origin of the inferior mesenteric artery at the aorta and divide with hemlock.

B. Cancer in the middle/lower rectum

  • Dissect the inferior mesenteric artery at the origin of the left colic artery and further along this to the ascending branch of the left colic artery (the inferior mesenteric vein is located close to this crossing).
  • The inferior mesenteric artery is divided with hemlock just distal to the origin of the left colic artery. Possible branches of this artery are divided while the main stem of the left colic and ascending branch are left intact to assure an adequate circulation of the left colon/ sigmoid. Fat with lymph nodes may be dissected off central parts of the superior mesenteric area and removed en-bloc with the lymph nodes at the origin of the left colic artery.
  • During this dissection the main sympathetic nerves must be visualized and retracted posteriorly to avoid injury. Avoid dissection into the parietal fascia in front of the aorta and posterior abdominal wall. If the proper vessel wall is visualised the dissection has been carried on too deeply and the nerve plexus may have been injured.

Step 4 – Finish the dissection of the sigmoid.

  • Grip the divided mesenteric inferior artery and lift it forward.
  • Continue the dissection in the mesocolic plane till the lateral abdominal wall behind all  the descending colon till the pelvic entrance. Carefully sweep the nerves posteriorly.
  • From the anterior dissect the sigmoid until the left colon, sigmoid and the upper rectum is completely free.

Step 5 – Total mesorectal excision

  • Extend the peritoneal incision on the posterior abdominal wall (medially) down to rectovesical pouch.
  • Incise the peritoneum transversally in front around 1 cm above the pouch. In female the dissection is performed along the dorsal wall of the vagina.
  • Tips: The proper plane may be difficult to identify on the top of the vagina. With a swab on a stick in the vagina this can be lifted up and forward to simplify the anatomy. In male the wall of the vesicles should be identified and followed on is posterior aspect and further on behind the prostate. It is recommended that the dissection from above is initially stopped 1-2 cm down behind the prostate, the rest can be performed after the posterior dissection.
  • Continue presacrally on to the rectum in the dissection plane developed behind the sigmoid which is the mesorectal plane (Heald’s holy plane”).
  • Dissect in this plane on the outside of the mesorectal fascia from 3-9 o’clock (4-8) as far down as possible. The dissection is then continued from the front and eventually the areas 2-3 and 9-10 are divided.
  • The dissection often has to be performed shifting from dorsally- anteriorly- laterally but the aim should be to go far down behind before continuing in front leaving the lateral dissection lastly. An initial presacral dissection permits the rectum to be lifted up and forward which facilitate the rest of the dissection. The plane is most difficult to identify laterally which is where the nerves are most frequently injured.
  • Fulfilment of the distal dissection.

Step 6 – Low anterior resection

  • For tumor of the upper rectum the mesorectum is dissected 5 cm anally to the lower border of the tumor.
  • Continue right angled through the mesorectum to the bowel tube at the proper level, thus avoid coning in on the specimen which will render the anal resection margin less than 5 cm.
  • For tumor in the middle/lower rectum the dissection is continued all along to the pelvic floor, and if desired further on to the upper part of the anal canal.
  • Prepare a free bowel wall along the whole circumference. Flush the rectum.
  • Divide the rectum with stapler and try to leave the row of staplers perpendicular on the bowel and close it with one magazine of staplers. More staple shots increase the chance of leakage. Avoid Z-lines.

Situations can develop when it is impossible to divide the bowel sufficiently far anally. Conversion to an open procedure should then be performed.

Transanal-TME (ta-TME)

  • The dissection from above is finished at the level of the middle rectum.
  • The dissection from below is performed up to this level.

Step 7 – Exteriorization of the specimen and division of the oral bowel tube.

  • Make a 6 cm incision transversally above the symphysis (Pfannenstihl incision).
  • Incise the fascia in front of the rectus muscle similarly.
  • Lift both edges of the fascia with Kocker’s forceps and dissect it off the underlying muscle. The dissection must be sharp in the midline.
  • Retract both rectus muscles from the midline.
  • Incise the peritoneum.
  • Apply plastic protection to the edges of the wound and exteriorize the specimen with the central vessels.
  • Divide mesentery and bowel at intended location.
  • Cut with scissors in the vascular arcade close to the bowel to visualize adequate blood circulation in the oral bowel end (adequate systolic blood pressure during the test?). Move further orally on the colon in case of inadequate bleeding.
  • Insert the “hat” of the circular stapler and close with a purse-string suture.
  • Interiorize the colon.
  • Close the abdomen.

Step 8 – Anastomosis

  • Insert the circular stapler very carefully and perforate the bowel with the pin just in front of or behind the staple row.
  • Attach oral and anal parts of the stapler while controlling the rotation of the bowel. Close the stapler and visually control for possible interposition. Fire the stapler.
  • Test the anastomosis enclosed by water and with air in the rectum.
  • Retract the omentum over the small bowel.

Step 9 – Laparoscopic control and closure of ports.

  • Repeat inspection of the abdominal cavity for possible iatrogenic injury.
  • Close the ports.


  • The patient is mobilized in the evening the day of surgery, or possibly the next day.
  • The patient can start to drink and eat carefully on the first postoperative day.
  • A potential wound drainage is removed when there is no longer fresh blood, usually on the first or second postoperative day.
  • The urinary catheter is removed on the fifth postoperative day.
  • The epidural catheter is usually removed on the second or third postoperative day and the patient continues on peroral analgetics.


  • Cardiopulmonary complications depend on the patient´s general condition, comorbidity and the extent of the surgery. Cardial infarcion and arrytmias and dysrhythmia may occur. Basilar atelectasis and/or pleural fluid and possibly pneumonia are more common.
  • Approximately 5% develop anastomosis leakage. Preoperative radiation therapy increases the risk of leakage. Intraperitoneal and/or pelvic infections, diffuse or localized, are rare in the absence of anastomotic leakage.
  • Intraabdominal bleeding, inclusive bleeding from anastomosis is relatively rare.
  • After open surgery wound dehiscence and infection in the abdominal wound occur varying degrees, from light superficial infection to abdominal wall abscess.
  • Paralytic ileus is common in the presence of another complication but can also appear without any specific cause.
  • Mechanical ileus is relatively rare, but if there is a lack of intestinal activity in the first week and increasing abdominal pains, a mechanical ileus is suspected.
  • Port-site hernia occurs after a laparoscopy.
  • Deep vein thrombosis and lung embolism are rare if prophylaxis is used according to guidelines.
  • Urinary retention.

Late complications

  • Ventral hernia in the abdominal wound may occur.
  • Postoperative ileus occurs in about 5%.

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