Anterior resection with total mesorectal excision
R.J.C. STEELE, Professor of Surgical
Oncology, University of Dundee
J.R.Coll.Surg.Edinb,
44, Feb 1999, 40-45
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The operation of anterior resection with total mesorectal excision (TME) has become the gold standard for the treatment of cancer of the rectum, except where the tumour is close to or involving the anal sphincter complex. The reason for this relates to the low incidence of local recurrence after this procedure, which has now been reported by several independent groups. (1-3) Although controversy still exists around the role of TME in tumours of the upper rectum, it is now widely accepted for tumours of the middle and lower third. (4)
The procedure has two main drawbacks. Firstly, there is a high risk of anastomotic breakdown (in the region of 15%) (5) , and many surgeons use a defunctioning ileostomy to ameliorate the effects of this complication should it occur. Secondly, it can be associated with a high incidence of urgency and faecal leakage, and, on the basis of evidence from functional studies and randomised trials, it is becoming standard practice to fashion a short colopouch to improve functional results.( 6)
Prior to surgery, patients should be fully investigated to exclude synchronous tumours and metastatic disease; bowel preparation, deep vein thrombosis (DVT) prophylaxis and perioperative antibiotics are also mandatory. (4) Furthermore, it is very important to ensure that the patients are fully conversant with the implications both of the disease and the operation, and are prepared for stoma formation. It follows that they should be seen by a stomatherapist before operation and, where possible, by a colorectal cancer specialist nurse. (4)
Finally there is the question of adjuvant radiotherapy. The recent Stockholm II trial indicates that short course preoperative (25 Gy in 5 fraction sin the week before surgery) reduces local recurrence rates and improves survival when used with conventional surgery, (7) but its role in conjunction with TME is far from clear. For this reason the MRC CR07 trial has been initiated, and, where any doubt exists, patients should be entered into this trial. It should be stressed, however, that this applies only to operable tumours. If a rectal tumour is fixed to the pelvis, then a long course of radiotherapy (e.g. 45 Gy in 20 fraction over four weeks) followed by a wait of about six weeks should be tried in an attempt to render the tumour operable.
The patient is positioned in the extended Lloyd-Davis position. It is important that the legs are not angled too steeply, as this will restrict the operative field. A urinary catheter must be inserted but this can be done during the operation as a supra-pubic procedure. This is particularly preferable in males. A nasogastric tube is not used routinely.
A long mid-line incision from the symphysis pubis to the xiphisternum is made. The skin is opened using cutting diathermy and the subcutaneous tissue using coagulation diathermy. In order to identify the midline in an obese patient, the subcutaneous tissue is split by the surgeon and the assistant using opposing finger traction. The linea alba and the fascia below the umbilicus is divided using coagulation diathermy and the peritoneum is opened close to the umbilicus using a knife to avoid burning underlying bowel. After a thorough laparotomy, looking particularly for liver metastases, intra-abdominal spread, lymphadenopathy and local spread, the small bowel is packed away into the right upper quadrant. This pack is held in place using a large blade of an "Omnitract" self-retaining retractor. Two further blades are then used to retract the left abdominal wall as far laterally as possible. With the surgeon on the left-hand side of the patient, the first assistant on the right-hand side and the second assistant between the legs, dissection can now begin.
Mobilisation of the left colon
The first assistant holds up the sigmoid colon with firm but gentle traction. Using hand-held diathermy and a pair of DeBakey's forceps, the surgeon then divides congenital adhesions between the sigmoid colon on the left lateral wall to expose the peritoneal reflection. The peritoneal reflection is then incised with the diathermy a few millimetres posterior to the "white line". This will expose the embryonic plane of dissection, which must now be developed using counter-traction with the DeBakey's forceps or a gauze swab (see Figure 1).
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This plane is encouraged to develop with use of gentle coagulation diathermy. When small vessels are encountered, these can be coagulated either directly or by grasping the vessel with the DeBakey's forceps and applying the diathermy.
This process continues to the base of the sigmoid mesocolon until the hypogastric nerves are encountered. In this way the ureter is swept laterally and cannot come to damage. Although not absolutely necessary if the nerves have been positively identified the ureter is usually seen at this stage. The plane immediately anterior to the hypogastric nerves is then followed down into the pelvis until the plane between the mesorectum and the sacral fascia has been identified. Further rectal dissection is then postponed until later in the operation. The plane of dissection is then extended superiorily, mobilising the whole of the left colon to the midline until the splenic flexure is reached.
Mobilisation of the splenic flexure
If the spleen is easily visible at this point and there are obvious adhesions between the omentum and the splenic capsule, these can be divided to avoid tearing the capsule when traction is placed on the omentum. If, however, the spleen is not visible, then no specific attempts are made to do this. The peritoneal connection between the lateral abdominal wall and splenic flexure is divided with diathermy as far as is comfortably possible. The mid-point of the transverse colon and the attached greater omentum are then grasped and traction applied to expose the plane between the omentum and the transverse mesocolon. This plane is entered and developed using coagulation diathermy (see Figure 2) and followed down to the splenic flexure. As long as the mesentery of the descending colon has been sufficiently mobilised during stage 3, this manoeuvre will bring about rapid mobilisation of the splenic flexure. It may be necessary to divide strands of tissue immediately above the splenic flexure and this is often best performed using the blunt-nosed Lloyd-Davis scissors.
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Completion of the mobilisation of the left colon
Attention is now turned back to the base of the sigmoid meso-colon and the peritoneum over its right aspect is divided taking care not to damage the underlying hypogastric nerves. The division of the peritoneum continues superiorly just anterior to the aorta until the origin of the superior mesenteric artery is encountered. This is dissected out carefully using McIndoe's scissors, ligated and divided. Further superior dissection leads to the inferior mesenteric vein, which is likewise ligated and divided at the inferior border of the pancreas, close to its origin (see Figure 3).
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This will now leave the large bowel from the transverse colon to the distal sigmoid extremely mobile and good perfusion is usually maintained up to the top of the rectum. This degree of mobilisation is essential to ensure a tension-free anastomosis.
It is usual practice to divide the colon at the apex of the sigmoid colon unless this is badly affected by diverticular disease, in which case it may be necessary to use the descending colon. The sigmoidmesentry is divided up to the colonic wall, making sure that both the ligated trunks of the inferior mesenteric artery and inferior mesenteric vein are included in the resection specimen. The sigmoid colon is then divided using a ligating and dividing stapler and the proximal bowel is packed up into the left upper quadrant of the abdomen and held in place with a deep retractor blade.
The rectum is pulled firmly forward and this will reveal the plane between the mesorectum and sacral fascia with the hypogastric nerves lying on it. This loose areolar plane is then gradually developed using the coagulation diathermy, always making sure that the nerves are separated from the surface of the mesorectum. By keeping the hypogastric nerves in view and preserving them, this will also reduce the risk of damaging the less obvious parasympathetic nerves and the parasympathetic plexus on the lower lateral wall of the pelvis. When posterior dissection has progressed as far as is comfortable, dissection moves to the right and then to the left of the rectum. Firmly pulling the rectum in the opposite direction and using a St Mark's retractor to apply counter-traction, will allow visualisation of the correct plane of dissection. After as much posterior and lateral dissection as can be comfortably accomplished has been done, attention is turned to the anterior dissection. In the female, it may be useful to hitch up the uterus by passing sutures underneath the two fallopian tubes and tying them to the anterior abdominal wall. The sutures should pass through the skin to remind the surgeon to replace the uterus at the end of the procedure. The peritoneum is then divided immediately above and anterior to the apex of the rectovesical or the recto uterine pouch. The anterior wall of the rectum is then retracted backwards and downwards by the surgeon's hand and counter-traction is obtained using a St Mark's retractor held by the third assistant. In the male, the plane is developed between the anterior mesorectum and the seminal vesicles (see Figure 4) and in the female between the anterior mesorectum and the vagina.
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Great care must be exercised to prevent excessive bleeding from the posterior wall of the vagina. When the anterior dissection has been performed it is then necessary to turn attention again to the sides and the posterior aspect of the plane of dissection. Lateral ligaments are not sought and clamped, as this is likely to damage the parasympathetic plexus. It is necessary however to divide the nerves from this plexus which supply the rectum itself (see Figure 5).
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The bleeding which is encountered during this dissection can nearly always be controlled by diathermy. In the pelvis it is useful to use long insulated diathermy forceps to avoid accidental diathermy injury or "shorting out" on metal retractors.
The final part of the rectal dissection is to ensure that the pelvic floor has been reached. This may require division of some posterior strands of tissue using the blunt-nosed Lloyd-Davies scissors. Once this has been achieved the very lowest part of the rectum just above the pelvic floor, should consist of a denuded muscle tube. A 30mm linear stapler is then inserted into the pelvis and the lower rectum is carefully manipulated into its jaws. The retaining pin is deployed and a line of staples is fired across the rectum at a point that is low enough to be clear of the distal limit of the tumour, but high enough to allow a further line of staples to be placed below it. The rectal stump is then washed out with povidone iodine solution to kill any intraluminal tumour cells. A further line of staples is then placed below the first line of staples but before releasing the stapler, the rectum is transected using a long handled knife on the stapler itself.
The stapled end of the proximal colon is brought down into the operative field and a 5cm pouch is formed using a single firing of an 80mm ligating and dividing stapler. Care must be exercised to make sure that mesenteric tissue is not incorporated into the staple line. The head of a 31mm circular end to end stapler is then inserted into the apical enterotomy of the pouch and secured in place using an over and over "purse string" suture of 2/0 prolene (see Figure 6).
One of the surgeons (usually the first assistant) inserts the circular stapler through the anal canal so that it abuts on to the staple line on the very short rectal stump. The centre rod (with sharp point) is then advanced, preferably through the centre of the staple line. The abdominal surgeon then ensures that the colon is not twisted and attaches the head of the gun on to the centre rod. The perineal surgeon then closes the staple gun and fires it (see Figure 7).
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After removal of the staple gun, the integrity of the anastomosis can be checked by direct palpation. The mucosal donuts should also be checked for integrity but these need not be submitted for histology, as the pathologist should check the distal resection margin of the main specimen for tumour involvement.
In all cases after total mesorectal excision a loop ileostomy is fashioned. This is done by excising a disk of skin about 2cm in diameter from the pre-marked site on the right side of the abdomen. A core of fatty tissue is also excised down to the underlying deep fascia. This is then incised with a cruciate incision and the underlying muscle and peritoneum split. All the dissection is done with diathermy. A point in the ileum some 20 to 30cm from the ileocaecal valve is identified for formation of the ileostomy. If the ileostomy is formed too close to the ileocaecal valve, this will hinder subsequent closure. Forceps are then passed through the mesentery immediately adjacent to the bowel wall and a soft catheter is threaded beneath the bowel wall. In order to ensure recognition of the proximal and distal limbs of the loop, one diathermy mark is made on the distal loop and two on the proximal loop. The soft catheter is then passed through the trephine in the abdominal wall in order to allow the ileum to be drawn on to the surface of the skin. Two suction drains are then placed into the pelvis in order to prevent the accumulation of haematoma behind the anastomosis, the pelvis and the lower peritoneal cavity are washed out and the wound is closed in a single layer using continuous number 1 PDS. The skin is closed using staples or a continuous subcuticular suture.
Attention is then turned to completing ileostomy. A near circumferential incision is made around the distal limb of the small bowel flush with the skin. This is then sutured to the inferior half of the trefine using 2/0 chromic catgut. Three sutures are then placed incorporating the skin, the ileal wall and the upper cut edge of the ileum in such an arrangement that when they are tied the proximal ileum is everted into a spout that is angled slightly downwards (see Figure 8).
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The supporting catheter can then be removed. This defunctioning ileostomy can be closed once a water soluble contrast enema, performed at three weeks or later, shows no evidence of leakage and when any oedematous swelling of the stoma has completely settled. In practice, this is usually around the sixth post-operative week.
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