8. ANTERIOR RESECTION OF THE RECTUM

Introduction

Having learnt the basic techniques it is now time to apply these to a more challenging task, namely the performance of an anastomosis in a situation where access is limited. For the purposes of the course we will demonstrate a technique that is useful in the performance of an anastomosis in the pelvis. However, you may find that access is limited for some oesophago-gastric or biliary-enteric anastomoses. Although a different technique may be used in these situations compared to that demonstrated here, they can still be performed by modifications of the basic techniques which you have learnt. It may also be that you would wish to perform a stapled anastomosis and this is certainly an option for an anterior resection, in the same way that a sutured anastomosis may be preferred for the oesophago-jejunal anastomosis discussed in the previous section. The modern surgeon should be able to perform both stapled and sutured anastomoses and select the most appropriate for the task being performed.

1. Adequate exposure

The patient should be placed in the Lloyd Davies position with their legs elevated. This will allow an assistant to stand between the legs and provide important retraction. It is also essential that a catheter is placed in the urinary bladder, as a full bladder will certainly obscure your view of the pelvis. The pelvis is frequently difficult to visualise and you should consider the use of a headlight. As the operation progresses you will certainly want to change the position of the table and perhaps where you stand but start on the patient's right side with the table level.

A long mid-line incision is the usual for an anterior resection. This should extend down to just above and superior to the pubis to a level that facilitates mobilisation of the splenic flexure.

Care should be taken to ensure that the bladder is not injured as the wound is opened in the lower portion of the abdomen. After the abdomen is opened a wound towel is used to protect the wound from potential contamination. The insertion of a self-retaining retractor (Balfour or Golingher) is also advisable. Further retraction is going to be necessary so ensure that you have adequate assistance.

2. Assessment of the situation

The assessment of a rectal cancer should have commenced pre-operatively and a decision will have been made as to whether pre-operative radiotherapy is required and as to whether an anterior resection or an abdominal peroneal excision of the rectum was required to clear the tumour. This will not be discussed further in this manual but the reader is referred to larger texts of colo-rectal surgery.

Assuming that the patient has been adequately staged pre-operatively and that you are planning a low anterior resection, you should start your peri-operative assessment with a full laparotomy. You may find unexpected liver or peritoneal metastases which may modify your surgical approach. Alternatively, the presence of an aortic aneurysm may make you think twice about performing an anastomosis.

As has been stressed before, ensure that you have adequate assistance for what is likely to be a challenging operation.

3. Preparation for an anterior resection

Preparation will have started pre- operatively with your staging of the tumour and assessment of the patient's general condition. Prophylactic heparin and antibiotics should have been administered and mechanical bowel preparation undertaken. Further description of the mobilisation of the rectum and colon may to be found in the "How do I do it?" section of the Journal of the Royal College of Surgeons of Edinburgh.(18)

It is usually necessary to mobilise the whole of the left side of the colon to beyond the splenic flexure to ensure that there will be a suitable piece of descending colon able to be brought down into the pelvis without any tension. The secret of mobilisation of the colon is finding the correct tissue plain at the start and sticking to it (Figure 8.1).

Figure 8.1 Division of the lateral adhesions of the sigmoid colon

In so doing the ureter and important retro-peritoneal structures will be kept out of harm's way. Mobilisation of the left side of the colon and the splenic flexure is usually best undertaken standing to the patient's right side.

Next, divide the inferior mesenteric vein close to the duodenum (Figure 8.2), identify the inferior mesenteric artery and ligate this close to its origin.

Figure 8.2 Ligation of the inferior mesenteric vein close to the duodenum

This vessel is often quite atherosclerotic and a double ligature may be helpful, but take care at this point to ensure that the ureter is not included in your ligature. Pick a suitable site on the descending colon for the anastomosis and divide the mesentery up to this point. Divide the bowel isolating the cut end with antiseptic-soaked swabs. Remember that the sigmoid colon does not usually have a very good blood supply after the inferior mesenteric artery has been divided and that it is frequently involved with diverticular disease. For these reasons the sigmoid colon should not be used for your anastomosis.

At this stage you may prefer to stand on the patient's left side. Divide the peritoneum on the right side of the mesentery which you have raised and continue this into the pelvis. Repositioning of the table with a degree of head-down tilt and packing the small bowel away in the right upper quadrant may be of use at this stage. Gentle anterior traction on the colon will allow you to enter the loose areolar tissue behind the meso-rectum. Sharp dissection of this tissue is required to ensure an oncologically-sound operation.

The right and left rectal ligaments should be coagulated and divided, Devonvillier's fascia divided and the rectum freed from either the vagina or the prostate and seminal vesicles.

Prior to division of the rectum a right-angled clamp is applied below the tumour and the rectum washed with chlorhexidene solution. Stay sutures are inserted and the rectum divided with care being taken to limit any potential contamination.

4. Set up of anastomotic site

Access to the pelvis is frequently difficult so you must ensure that everything is set up to optimise the exposure that you do have. Ensure that:

• The table is correctly positioned - head down
  
• The small bowel is packed away from the operative site
  
• There is adequate retraction in the pelvis
  
• Stay sutures on the rectum are holding it in a suitable position as are stay sutures on the proximal resection margin.
  
• The proximal bowel is correctly orientated.

For this anastomosis you will require longer instruments than you would use for a small bowel anastomsis. Just because the instruments are long does not mean that they cannot be of fine quality so ensure that the correct instruments are available and should be checked before you start. The use of a suture rack to hold the sutures after they have been placed is very helpful and will save a lot of frustration.

Prior to starting the anastomosis ensure that the operative field is dry and that all oozing points are coagulated.

5. Technique of anastomosis

A sero-submucosal suturing technique will be described and the end result will be similar to that described in Chapters 3,4 and 5. A modification is required as it will be impossible to rotate the bowel ends. Therefore, the posterior layer of the anastomosis is performed first.

Start by placing the first suture at the anti-mesenteric border of the proximal bowel end. Commence this suture from the inside starting in the submucosal layer and emerging at the serosa on the anti-mesenteric border. Now, using the same suture, come from the sero- muscular layer of the rectum out into the submucosal layer, break off the needle and hold the suture with a haemostat. Place a similar suture at the mesenteric border of the bowel and the left side of the rectum. It may be helpful to place your next stitch in the middle position of the back layer. Next, place sutures every 0.5 cm along the back layer of the anastomosis. After the suture has been inserted and the needle discarded, place it in a suture rack (Figure 8.3 & 8.4).

	Figure 8.3 Posterior layer sutures held in suture racks
	Figure 8.4 Posterior layer of sutures

Once the back layer has been completed ask an assistant to hold up the suture rack and then gently ease the proximal bowel down into the pelvis so that the rectum and colon are lying in approximation (Figure 8.5).

Figure 8.5 After insertion of the posterior sutures the colon and rectum are approximated

Now is not the time to find that there is any tension on the proximal loop of bowel.

Tie the sutures and grasp the two end sutures in haemostats, divide the remaining sutures (Figures 8.6, 8.7 & 8.8).

	Figure 8.6 Tying of the posterior sutures
	Figure 8.7 Division of the sutures after the knots have been tied and the spacing between sutures checked
	Figure 8.8 Completed posterior aspect of an anterior resection

A similar technique is now used on the anterior layer on the anastomosis except that the sutures will be tied on the outside of the bowel. Start by asking your assistant to lift the right-hand suture up gently as this will assist you in your placement of the next suture. Starting on the outside of the proximal colon and ending on the outside of the rectum an inverting sero-submucosal suture is inserted. Once this suture has been inserted, place the suture that your assistant is holding in the suture rack and have them hold the last suture while you place the next one approximately 5 mm away. In this way each suture helps in the placement of the next one until the anterior layer has been completed. As with previous interrupted techniques, tie the sutures at the end, check the spacings and cut the ends (Figure 8.9 a, b &c).

Figure 8.9      Completion of the anterior layer of an anterior resection

6. Post-operative care

For a low anterior resection many surgeons will cover the anastomosis with a loop ileostomy. In such cases closure should be considered after 6-8 weeks. Prior to closure of the stoma it is usual to check the anastomotic integrity with a contrast study.