The sequence of steps in performing a left colectomy is similar regardless of whether the technique is open or laparoscopic and also similar irrespective of the indication for the procedure. This is based upon the anatomy and blood supply of the left colon and the fact that postoperative anastomotic complications frequently occur secondary to tension upon the anastomosis due to inadequate colon mobilization. When performing a left colectomy, it is important to err on the side of mobilizing too much, rather than too little!
Anatomy of the Colon and Postoperative Complications
Three factors specific to the vascular anatomy of the colon are associated with postoperative complications:
The vascular supply of left colon anastomoses is frequently based upon the marginal artery. Significant traction upon or manipulation of this structure during surgery can lead to vessel avulsion or injury. This in turn can lead to postoperative ischemia with subsequent postoperative anastomotic stenosis or leak.
The inferior mesenteric vein, if not divided, can cause significant tension upon the anastomosis.
Failure to adequately mobilize the proximal bowel and/or splenic flexure can also result in anastomotic tension with possible ischemic stenosis and/or leak.
Remembering these three factors during an operation will lead to reduced complications and improved results.
There have been numerous reports regarding the need or lack of need of a bowel preparation prior to surgery. This is left to the surgeon’s discretion; however, multiple randomized studies have shown that preoperative bowel preparation is not necessary and may actually be associated with less favorable postoperative outcomes. If a transanal stapled anastomosis is to be performed, an enema should be administered prior to the procedure in order to clear the rectum. Antibiotic prophylaxis is recommended. This should be administered within 30 minutes of the incision time. I favor cefotetan 2 grams intravenously. If the procedure lasts more than 4 hours, this is redosed. In cases of penicillin allergy, ertapenem 1 g intravenously can be utilized. The most common errors in antibiotic dosing are receiving the prophylaxis more than an hour prior to incision or not redosing in cases of a surgery lasting longer than 4 hours.
If in doubt, the patient should be positioned in modified lithotomy position (Lloyd–Davies position). This permits a transanal stapled anastomosis to be performed and also facilitates positioning of an assistant between the legs as well as performance of proctoscopy for checking for anastomotic leaks. While not strictly necessary for handsewn anastomoses, it is so easy to position the patient preoperatively, and so cumbersome to do this once the patient is prepped and draped; I err on positioning patients this way even if I do not think this will be needed. Compression injury to the perineal nerve is possible, and proper padding of the lateral aspect of the lower extremities is important to avoid such injury. Care should be taken in having a sequential compression device placed on the patient preoperatively and in postoperative administration of low molecular weight heparin in high-risk individuals. Patients should only be in “modified” or low lithotomy position to avoid impeding the lower extremity venous return and to avoid significant reduction in lower extremity blood pressure.
Choice of Incision
The abdomen is entered through a lower midline abdominal laparotomy incision extending proximally just above the umbilicus. This can be extended superiorly, if required, secondary to a high splenic flexure. An easy landmark to remember is that the inferior mesenteric artery lies roughly at the level of the umbilicus, and for rapidity of surgery, with respect to
improved colon mobility and
high vascular ligation and clearance of “apical” lymph nodes in cases of colon cancer, division of the vascular pedicle at this point is easiest.
Splenic Flexure Mobilization
Splenic flexure mobilization is required in many cases of left colectomy in order to provide for a tension-free anastomosis. In performing splenic flexure mobilization, there are several important points to consider:
staying within the avascular plane between the omentum and colon/colon mesentery;
avoidance of traction upon omental attachments to the spleen, which can result in splenic capsular tears and bleeding;
avoidance of traction upon or compression of the marginal artery upon which subsequent anastomoses are based; and
avoidance of inadvertent entry into deeper retroperitoneal planes that can be associated with pancreatic injury and bleeding.
The easiest area to enter the space between the omentum and the colon is in the lesser sac. Here, there is a clear avascular plane (Fig. 1A–C) where the lesser sac can be entered and the avascular plane identified. This is divided using electrocautery approximately 1 cm away from the margin of the distal transverse colon, proceeding around the splenic flexure. Placing the surgeon’s index finger beneath this tissue permits the diaphanous nature of this tissue to be more apparent (Fig. 2A). Once the splenic flexure is taken down, mobilization is continued down the left gutter so that the colon mesentery is freed posteriorly from Gerota’s fascia (Fig. 2B). Using electrocautery, the white line of Toldt is scored along the left gutter down to the level of the pelvis. As the assistant places traction upon the sigmoid colon medially and toward the right, the surgeon can sweep the retroperitoneal structures (kidney, gonadal vein, ureter) posteriorly using a laparotomy pad.
Identification of the Inferior Mesenteric Artery and Vein
Just as in laparoscopy, the inferior mesenteric artery and vein can easily be identified by its relatively constant location. The inferior mesenteric vein is easiest to identify lateral to the ligament of Treitz (Fig. 2C). Since this area has been previously mobilized posteriorly (during splenic flexure mobilization), identification of the avascular space to either side of the vein is facilitated and the vein can be clamped, divided, and doubly ligated with 2-O silk suture. Once this has been accomplished, the areolar tissue between the inferior mesenteric vein and inferior mesenteric artery can be divided. If traction is placed upon the sigmoid colon, the inferior mesenteric artery can best be appreciated as a band-like structure arising from the aorta, tethering the bowel. There is an avascular plane just underneath the inferior mesenteric artery, below the arch of the superior hemorrhoidal artery, which can easily be identified even in obese individuals. The inferior mesenteric artery is similarly clamped, divided, and doubly ligated with 2-O silk suture. By performing a high vascular ligation in this manner, the entire blood supply of the left colon is divided as well as the significant colonic mobility necessary for all colorectal and low pelvic anastomoses provided.
Choice of Margins
In cases where surgery is performed for cancer, resection margins are chosen approximately 10 cm to either side of the lesion. The bowel at this point is divided using a linear stapling device, and the intervening mesentery then sequentially divided, ensuring that the inferior mesenteric artery is resected with the surgical specimen so that the pathologist can retrieve the “apical lymph node.” When surgery is performed for diverticular disease, the proximal margin should be selected based upon palpably normal “soft” bowel in contrast to the muscular hypertrophy characteristic of symptomatic diverticular disease.