Introduction

 Colon resection is the removal of part of or the entire colon, depending on the underlying etiology of the disease that necessitates the removal.[1][2]

Anatomy and Physiology

The colon derives embryologically from the midgut and hindgut.

It is divided into the cecum, ascending, transverse, descending, and sigmoid colon and rectum.

• Blood supply to the midgut portion (cecum to splenic flexure) derives from the superior mesenteric artery, namely ileocolic artery, right colic artery (inconsistent), and middle colic artery, which further divides into right and left branches.
• The blood supply to the hindgut portion (splenic flexure to rectum) derives from the inferior mesenteric artery, namely the left colic artery, sigmoid branches, and superior rectal artery.
• The superior mesenteric artery and inferior mesenteric artery connect at the splenic flexure via the marginal artery (of Drummond), thus enabling collateral supply.
• The distal part of the rectum derives additional supply from the internal iliac artery via the pudendal artery which gives rise to the inferior and middle rectal arteries.

Arteries, veins, and lymphatic drainage are located in the mesocolon, which during the oncological surgical resections of total mesorectal excision and complete mesocolic excision gets removed in its entirety corresponding to the part of the colon to be removed.

Indications

The commonest indication for surgical resection of the colon is a colorectal malignancy, and the resection should be carried out according to oncological principles:

• Resection margin 5 cm proximal and distal to the tumor for colonic malignancies
• Circumferential resection margin for rectum, distal margin of 2 cm adequate
• Remove vasculature and lymphatic drainage at the level of origin of the primary feeding vessel
• Thus allowing resection of locoregional lymph node-bearing mesentery for cure and staging
• The fashioning of a well-vascularized and tension-free anastomosis

Contraindications

Colonic resection is classified as major surgery and should not be undertaken if the patient is physically not fit to sustain a major procedure. Reversible and modifiable risk factors should be addressed before surgery, and postoperatively, a patient may require intensive or high dependency facilities.

Equipment

Colonic resection can be carried out via open (laparotomy) or minimal access (laparoscopic, robotic) approaches.

• The open approach requires a sterile operating theater, an operating table that allows removal of the end segment, and sidebars for mounting the attachments to place the patient's legs in a Lloyd Davies position. All instruments can be found in a major laparotomy set, including bowel clamps.
• The laparoscopic approach in addition to the above set up requires a gas insufflator, display screens, laparoscopic camera, and instruments.
• For the robotic approach, the robot is required.
• Equipment for bowel anastomosis would be suture material for a hand-sewn anastomosis (absorbable braided or monofilament, strength 3/0).
• Stapled anastomosis would require linear staplers for a side-to-side anastomosis (75 or 100mm in length), or a circular stapling device for an end-to-end anastomosis (diameter 28 mm to 33 mm, depending on patient size).
• For rectal surgery, a small extra table needs to be prepared with a proctoscope, bladder syringe, and lubricant to facilitate rectal washout and anastomosis.

Personnel

Colonic resection requires a full contingent of operating theater personnel (scrub side, anesthesia side, and assistant to position the patient), an anesthetist, and a team of surgeons (at least one operating surgeon and one assistant).

Preparation

Before surgery, the patient should be thoroughly evaluated.[3]

• The colonic evaluation consists of colonoscopy to assess the disease is necessitating resection, as well as ensuring that the remainder of the colon is normal (e.g., no synchronous tumors) and imaging modalities such as CT, to assess for the distant spread and stage the disease appropriately.
• Laparoscopic resection for small tumors requires the preoperative marking of the lesion with an endoscopic tattoo to enable intra-operative identification.
• Rectal cancers in addition to the above require an MRI scan of the rectum and/or an endorectal ultrasound.
• Prepare the patient pre-operatively according to local protocol. Most institutions will use bowel preparation and give intravenous peri-operative antibiotic prophylaxis.

Technique or Treatment

Bowel resection can be carried out as an open or laparoscopic procedure; the surgical principles remain the same.[4][5]

The key to adequate resection is the blood supply to the colon. Resection for benign disease does not need to be as extensive, but resection for malignancy should aim to resect the named colonic vessels supplying the cancer-bearing portion of the colon as close to their origin as possible to yield an adequate number of lymph nodes in the colonic mesentery (> 12).

The bowel proximal and distal to the resection have to be mobilized to allow a tension-free anastomosis, and the anastomosis should have a good blood supply. Depending on expertise and equipment available, a bowel anastomosis can be performed hand-sewn or stapled.

For example, a formal right hemicolectomy entails ligation of the ileocolic, right colic (if present), and right branch of the middle colic artery. Proximal bowel division is carried out at the terminal ileum, and distal bowel division at the transverse colon. The anastomosis is conventionally formed as a side-to-side between the terminal ileum and the transverse colon.

Resection of a sigmoid colon tumor entails ligation of the inferior mesenteric artery and inferior mesenteric vein. Proximal bowel division is carried out at the distal descending colon, and distal bowel division at the upper rectum, above the peritoneal reflection. The anastomosis is conventionally formed as an end-to-end between the descending colon and the upper rectum with the help of a circular stapling device inserted via the anal canal.

Complications

Procedure-related complications can be divided into complications encountered during the surgery and post-operative complications.[6][7][8]

Procedural complications include bleeding, most often venous in nature due to the handling of the mesocolon or during dissection of the greater omentum, and rarely from any of the named vessels.

However, an arterial bleed from the named vessels of the colon can be torrential and requires swift action, especially in laparoscopic procedures, where the bleeding can potentially obscure the view if it hits the camera.

Direct pressure where possible to temporarily arrest the bleeding buys time to strategize, reposition, request additional instruments, site further ports, if necessary, and definitively stop the bleed.

Another intra-operative complication is damage to surrounding structures. The structure most at risk is the left ureter. For left-sided surgery, it should always be identified. If an intra-operative injury (diathermy burn, transection) occurs and is recognized immediately, it can be repaired, and a ureteric stent should be placed to reduce the risk of stricture. If the injury is only diagnosed in the postoperative period, management depends on the extent and location of the injury, the general state of the patient, and the expertise available. A urological specialist should be consulted if available.

Post-operative complications include infections (wound, chest, urinary tract). Early mobilization, physiotherapy, incentive spirometry, and removal of urinary catheters can prevent infections. Wound infection risk in clean-contaminated surgery is greatly reduced by giving prophylactic antibiotics within one hour of skin incision.

Anastomotic leak is a dreaded complication for all surgeons performing colonic resection and primary anastomosis. A high index of suspicion is indicated if postoperatively, a patient does not progress as expected, as signs and symptoms can be subtle to start with, especially if the leak is in the pelvis and the patient has a defunctioning stoma. Patients may have pyrexia, tachycardia, cardiac arrhythmias (new-onset atrial fibrillation), complain of abdominal pain and bloating, and have a distended, tender, and potentially peritonitic abdomen. Inflammatory markers will be raised more markedly than expected in the postoperative period. Free air under the diaphragm may not be visible on an erect chest x-ray, but CT will show pneumoperitoneum and fluid around the anastomosis. In patients who have undergone anterior resection, it is advised to perform the scan with rectal contrast.

Depending on the severity of the leak and the patient's general state, the management can include all or parts of the following: 

• antimicrobial therapy, 
• drainage of pus collections (percutaneously if patient stable and expertise available), and 
• consideration for a re-look surgical procedure to wash and drain the abdominal cavity, inspect the anastomosis, and either defunction the patient or take the anastomosis apart and bring out the proximal bowel as an end stoma (akin to a Hartmann's procedure).

Clinical Significance

Prerequisites For Good Anastomosis

• Adequate blood supply: consider patient factors during surgery (functional like blood pressure or inotropes; organic like peripheral vascular disease, calcified vessels, or thrombosis, plaques)
• Other colonic pathology (diverticulosis, proximal dilatation in obstructed cases)
• Tension-free (adequate length of the bowel, adequate length of the mesentery)  

Adequate length of the colonic conduit for anterior resection:

• Divide the IMV as high as possible (landmark is the DJ flexure, divide cephalad to last visible tributary, divide the peritoneum taking care not to injure the marginal artery
• Full mobilization of the splenic flexure. Check that the conduit reaches the symphysis pubis – then it will reach the pelvis for a colorectal anastomosis
• Check that the conduit reaches the symphysis pubis, then it will reach the pelvis for a colorectal anastomosis

Enhancing Healthcare Team Outcomes

While colon resection is done by the surgeon, the monitoring of the patient and preoperative workup is usually done by the anesthesiologist. Both before and after surgery, the nurse plays a vital role in bowel preparation and postoperative monitoring. The patient must have deep venous thrombosis prophylaxis and must be taught how to use the incentive spirometer. Physical therapy is usually consulted for ambulation of the patient in the post-operative period. [9][10]

Evidence-based Outcomes

Today elective colon resections have excellent outcomes. Most patients have a short stay in the hospital of about four days. By paying attention to detail, the risk of wound infection is also minimized. Current data indicate that laparoscopic colectomy is as effective as open colectomy in preventing recurrence of cancer. Further, several clinical trials have shown that the risk of seeding is not increased at the port sites.[11] [Level 2]