CHAPTER 16 Colectomy
BACKGROUND
There are many indications for both partial and total colectomy. These include malignant, benign, ischemic, inflammatory, and infectious processes. The most common indications for colon and rectal resection are addressed individually later in the chapter. Common terms used to describe the types of colon and rectal operations are described in Table 16-1.
TABLE 16-1 Common Colon Procedures
| Type of Resection | Description |
|---|---|
| Segmental colectomy | Removal of a portion of the colon (e.g., right, transverse, left, or sigmoid). |
| Total abdominal colectomy | Removal of the entire abdominal colon, leaving the rectum and creation of an end ileostomy or ileorectal anastomosis. |
| End stoma | Intestinal diversion involving division and exteriorization of the colon (colostomy) or terminal ileum (ileostomy) through the skin. The distal colon is then either brought out as a mucous fistula or left in the abdomen as a Hartmann’s pouch. |
| Loop stoma | A loop of either colon or ileum is exteriorized and opened, but not divided. |
| Hartmann’s pouch | An end stoma is created from proximal bowel; distal bowel is closed and remains in the pelvis. |
| Ileal pouch–anal anastomosis (Park’s pouch, J-pouch) | After total proctocolectomy, the terminal ileum is used to create a reservoir that is connected to the anus as a “neorectum.” |
| Total mesorectal excision | En bloc removal of the mesorectum along with the rectum for rectal cancers of the mid and distal rectum. This is carried out by dissection in the plane between the fascia propria of the rectum and the presacral fascia. |
| Low anterior resection | Resection of the upper rectum; an anastomosis is formed between the colon and distal rectum. |
| Abdominoperineal resection | Total mesorectal excision of the rectum, surrounding tissues, and lymph nodes via abdominal and perineal approaches; creation of an end stoma. |
| Total proctocolectomy | Removal of the entire colon and rectum. Ileoanal pouch reconstruction or end ileostomy is required. |
INDICATIONS FOR COLORECTAL RESECTION
I. Sporadic Cancer and Inherited Polyposis Syndromes
A. Colon adenocarcinoma is the third most frequently diagnosed cancer and the second most common cause of cancer death in the United States. Surgical resection is the initial treatment of choice for most colon cancers, although postoperative (adjuvant) chemotherapy plays an important role in the management of patients with nodal metastases. Surgery is aimed at removing the primary cancer with tumor-free margins, as well as the associated bowel mesentery and regional lymph nodes. In practice, the extent of resection is dictated by the location of the lesion and the colonic blood supply. For example, cecal tumors are treated with right hemicolectomy, an operation that involves ligation of the ileocolic, right colic, and right branch of the middle colic vessels, and resection of the segment of colon fed by these vessels. When curative resection is not possible, resection of the primary tumor is often still indicated to prevent complications associated with large tumors (e.g., obstruction and bleeding).
B. Rectal Adenocarcinoma: Because of the extraperitoneal position of the rectum within the pelvis (which allows for the administration of radiation therapy) and its proximity to parasympathetic and sympathetic nerves, rectal cancers are treated differently than are cancers of the colon. In the absence of nodal metastases, smaller lesions are typically treated with surgical resection and regional lymphadenectomy or with transanal local excision. The treatment of more advanced rectal cancers includes radiation and chemotherapy given before surgical excision of the tumor (i.e., neoadjuvant therapy). Large tumors may shrink significantly after chemoradiation, allowing for resection of most rectal cancers, with preservation of the anal sphincters (i.e., low anterior resection). In contrast, the distal location of some rectal cancers precludes sphincter preservation, despite neoadjuvant therapy, and mandates abdominoperineal resection (APR).
C. Adenomatous Polyps: Most colorectal carcinomas are believed to develop from adenomatous polyps. Polyps are generally classified by gross appearance as either pedunculated (i.e., with a stalk) or sessile (i.e., flat). Histologically, polyps are classified as tubular, tubulovillous, or villous. Tubular adenomas are the most common subtype, constituting 75% or more of colorectal adenomas, and have the least malignant potential of the three subtypes. Villous polyps constitute approximately 10% of colorectal adenomas, are most often found in the rectum, and have the greatest malignant potential. Polyps identified at colonoscopy should be excised completely. If complete endoscopic excision is not possible, segmental colectomy is indicated. If invasive carcinoma is found in the head of a pedunculated polyp, endoscopic resection is adequate treatment. Poorly differentiated histology, lymphovascular invasion, and the presence of invasive tumor within 1 mm of the resection margin mandate segmental colectomy.
D. Familial adenomatous polyposis (FAP) is an autosomal dominant genetic syndrome most often associated with mutations of the APC gene. Patients with FAP have in excess of 100 precancerous polyps throughout the colon as early as their teens. If untreated, nearly all of these patients have colon cancer by age 40 years. Attenuated FAP is a phenotypic variant of the classic syndrome that is characterized by later onset of polyps, fewer polyps, and rectal sparing. The treatment of FAP is prophylactic surgical resection, usually performed after the onset of puberty. Surgical options include total proctocolectomy with permanent end ileostomy, total proctocolectomy with ileal pouch–anal anastomosis (IPAA) and total abdominal colectomy with ileorectal anastomosis. The latter option should be offered only to carefully selected patients because it leaves the rectum in place, necessitating close subsequent surveillance. Patients with the attenuated FAP phenotype are sometimes offered a rectal sparing procedure, whereas patients with classic FAP are generally offered total proctocolectomy.
E. Hereditary nonpolyposis colon cancer (HNPCC) accounts for 5% to 7% of all colon cancer diagnoses. HNPCC is inherited in an autosomal dominant pattern and has been linked to mutations in DNA mismatch repair genes. The Amsterdam criteria are used to identify patients at high risk for HNPCC. In such patients, screening colonoscopy is recommended beginning at age 20 to 25 years. Total abdominal colectomy with ileorectal anastomosis is recommended if an adenomatous polyp or a colon carcinoma is identified. Patients with HNPCC are at an increased risk for rectal cancer, and annual proctoscopy is mandatory after colectomy.
II. Inflammatory Bowel Disease
A. Ulcerative colitis (UC) is a chronic inflammatory disease of the large intestine. The disease is marked by inflammation and ulceration of the bowel mucosa beginning at the rectum and extending proximally. UC is associated with a significantly elevated risk of colorectal cancer, and patients require frequent colonoscopic surveillance. There is no medical cure for UC, and current medical treatment is aimed at suppressing the inflammatory process. Although many patients remain symptom-free for prolonged periods, up to one third of patients ultimately require surgery.
1. Indications for surgery include intractable symptomatic disease despite medical therapy and the presence of dysplasia or cancer. Total proctocolectomy with ileostomy and total proctocolectomy with IPAA are curative and eliminate the risk of colon or rectal cancer.
2. Emergent indications for surgery in patients with UC include massive bleeding and toxic megacolon. Toxic megacolon occurs in approximately 10% of patients with UC and is characterized by acute dilation of the colon, accompanied by diarrhea, abdominal pain, fever, tachycardia, and leukocytosis. Initial treatment involves aggressive intravenous hydration, antibiotics, steroids, and cessation of narcotic pain medications. A worsening clinical appearance mandates surgical intervention, typically, total abdominal colectomy and creation of an end ileostomy.
B. Crohn’s disease is an inflammatory disease that may affect any segment of the gastrointestinal (GI) tract. Disease limited exclusively to the colon occurs in approximately 15% of patients. As with UC, the initial treatment for Crohn’s colitis is medical. Surgical indications include failure of medical management, intestinal obstruction, fistula, fulminant colitis, toxic megacolon, massive bleeding, cancer, and malnutrition. Because more than half of all patients with Crohn’s disease experience a recurrence within 10 years of surgery, conservation of bowel length is an important surgical principle. The amount of colon resected depends on the extent and location of disease.
III. Benign Conditions
A. Diverticulitis results from microperforation of colonic diverticula. In uncomplicated diverticulitis, this perforation is contained and manifests as colonic and pericolonic inflammation. Diverticulitis may be complicated by abscess formation, fistulization between the colon and adjacent structures, free perforation, or obstruction. Initial episodes of uncomplicated diverticulitis are treated medically with antibiotics and dietary restriction until symptoms resolve. Recurrent uncomplicated diverticulitis and complicated diverticulitis are indications for surgical resection. In the stable patient with recurrent or complicated diverticulitis, medical treatment should be instituted to treat symptoms and reduce inflammation. After symptoms have subsided for at least 3 weeks, a colonoscopy should be performed to confirm the presence of diverticula, document the extent of disease, and exclude the presence of a neoplasm. Segmental resection of the involved colon, most commonly the sigmoid colon, with primary anastomosis can then be performed. Patients with complicated diverticulitis and evidence of free colonic perforation or sepsis should be operated on emergently and resection of the involved colon undertaken. Creation of a temporary colostomy, rather than an anastomosis, is often the preferred approach in such settings.
B. Sigmoid volvulus results from the torsion of the colon on its mesenteric axis. Volvulus may result in partial or complete obstruction of the bowel lumen, vascular compromise, bowel wall ischemia, and perforation. More than 80% of colonic volvuli involve the sigmoid colon. Patients are typically elderly, chronically debilitated, immobile, and institutionalized and present with abdominal distention, pain, and obstipation. Evidence of perforation and clinical deterioration are indications for emergent operative intervention, including sigmoid resection. In patients who are stable, reduction of the volvulus may be accomplished initially via colonoscopy or proctoscopy. Recurrence rates after endoscopic decompression are as high as 80% to 90%, and elective sigmoid resection should subsequently be undertaken.
C. Cecal volvulus, which is less common than sigmoid volvulus, is most commonly caused by congenital incomplete peritoneal fixation of the cecum in the right lower quadrant. Presenting symptoms are similar to those associated with sigmoid volvulus. Plain radiographs of the abdomen show a dilated cecum, often displaced to the left side of the abdomen. Endoscopic decompression is rarely successful. Treatment of suspected cecal volvulus, therefore, should include prompt right hemicolectomy, even in stable patients. In patients who cannot tolerate a lengthy procedure, surgical decompression and cecopexy (i.e., detorsion of the colon and fixation of the cecum in the right lower quadrant) is an acceptable alternative procedure, albeit one associated with a significant rate of recurrence.
D. Lower GI bleeding is most often caused by diverticulosis (50%) or arteriovenous malformations (30%). The initial treatment of lower GI bleeding includes resuscitation, correction of coagulopathy if present, and localization of the bleeding site. In 80% of patients with a diverticular bleed, bleeding stops spontaneously. In other patients, colonoscopic approaches or angioembolization can be used to control bleeding. Patients who continue to bleed require surgical intervention. Optimally, the site of bleeding is localized preoperatively with angiography, Technetium-99m–tagged red blood cell nuclear medicine scan, or colonoscopy, allowing for segmental resection of the involved colon. When preoperative localization is not possible, total abdominal colectomy is the procedure of choice.
E. Infectious colitis is most often treated with antibiotics, but occasionally necessitates colectomy. Pseudomembranous colitis is caused by the toxin-secreting bacterium Clostridium difficile. Most prevalent in hospitals and nursing home settings, pseudomembranous colitis is almost always associated with the previous use of antibiotics. Patients typically present with watery diarrhea and crampy abdominal pain. Generally, a course of oral metronidazole or vancomycin is adequate treatment for uncomplicated pseudomembranous colitis. Rarely, severe infection can lead to progressive colonic dilation, ischemia, and even perforation. In such fulminant cases, total abdominal colectomy with temporary ileostomy is required. The rectum is spared and an ileorectal anastomosis can be performed months later, when the patient is stable and well nourished.
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