The most common causes of lower GI bleeding are, in order of decreasing frequency, diverticular disease, carcinoma of the colon, inflammatory bowel disease, colonic polyps, vascular ectasias, ischemic colitis, rectal ulcers, and hemorrhoids, together with several very rare disorders (1). Algorithm 14.1 outlines a management algorithm for the workup for heme-positive stools.

Adenocarcinomas are the most common malignant colorectal tumors. Other malignant tumors are carcinoids, GI stromal tumors, primary lymphomas, and metastatic tumors originating from other organs (2). The most frequently encountered neoplasms are adenomas and adenomatous polyps (discussed later in this chapter).

Cancer of the colon and rectum is the third most commonly diagnosed malignancy and the second leading cause of cancer deaths in men and women in the United States. In 2002, an estimated 107,300 new cases of colon cancer and 41,000 new rectal cancers occurred. An estimated 56,600 patients died in 2002 from colorectal cancer. Importantly, nearly 50% of patients diagnosed develop metastases within 5 years. However, mortality from colorectal cancer has decreased over the past several decades (3).

The arteries that supply the colon are paralleled by veins of the same names. The superior and inferior mesenteric veins join the splenic vein, which drains into the portal vein to the liver. Thorough review and knowledge of this anatomy is essential to a successful surgical resection.

The lymphatic drainage of the colon parallels the venous channels. Lymph nodes may be found in the colonic mesentery, the mesorectum, and the para-aortic area. Low-lying cancers of the anal canal may spread to the deep inguinal nodes, and tumors of the anus may spread to the superficial inguinal nodes.

Average-risk, asymptomatic patients should undergo colorectal cancer screening at age 50. The most commonly used method is annual fecal occult blood test plus flexible sigmoidoscopy every 5 years. Colonoscopy can be performed every 5 to 10 years or double-contrast barium enema every 5 years. Virtual colonoscopy using computed tomography (CT) or other imaging modalities is not yet recommended (4, 5, 6).

The surgical treatment of colon tumors depends on their location. For single lesions, a segmental resection is usually performed, whereas for synchronous lesions, a more extensive resection may be required. Standard surgical procedures according to the location of the tumor include right hemicolectomy, transverse colectomy, left hemicolectomy, and sigmoid colectomy, with the corresponding mesentery and mesenteric lymph nodes included in the resection. A surgical margin of at least 2 cm is desirable, both proximal and distal to the tumor (7).

Laparoscopic treatment for many nonmalignant diseases now is preferred over a traditional open operation. For laparoscopic-assisted colectomy, several small ports are introduced into the peritoneal cavity and pneumoperitoneum is established. Laparoscopic staging is performed, the colon is mobilized, and the vascular pedicle ligated and divided. The tumor-containing colon is then exteriorized through a small incision. Standard extracorporeal techniques are used to divide the colon and perform the anastomosis. Weeks et al. described the results of a multicenter prospective randomized trial comparing laparoscopic-assisted versus open colectomy for colon cancer. Only minimal short-term quality of life benefits were found in patients undergoing laparoscopic-assisted colectomy. Survival data from this study are not available (8,9).

The role of laparoscopic colectomy for colon cancer remains controversial and is continuing to be evaluated in trials. In the 2003 guideline, the National Comprehensive Cancer Network did not recommend laparoscopic colectomy.

An appropriate preoperative staging evaluation for colon cancer patients includes chest radiograph, colonoscopy, complete blood count, platelet count, carcinoembryonic antigen (CEA) level, and pathology review. The routine use of abdominal-pelvic CT is controversial. For rectal cancer, abdominal-pelvic CT is useful because the finding of metastatic disease may alter treatment decisions. In addition, endorectal ultrasound (ERUS) should be performed on patients with rectal cancer.

The CEA level, an important tumor marker, should be established preoperatively so that subsequent levels can be monitored. Abnormal preoperative liver function tests in patients with colonic malignancy are of concern and may suggest metastatic disease in the liver.

In patients with rectal cancer, the most important step is preoperative determination of the stage of the patient’s disease. Again, history and physical examination, including a digital rectal examination and, for women, a pelvic examination, are very important. Patients with rectal tumors should undergo CT of the abdomen and pelvis.

ERUS is the most accurate method for staging local tumors. When performed by an experienced surgeon or radiologist, this procedure can disclose the depth of invasion with an accuracy of 85% to 90% and predict any nodal metastases with an accuracy of 85%. ERUS can help identify candidates for local therapy, patients who need radical surgery, and patients who would benefit from preoperative radiation therapy.

Three principles direct preparation of the colon for surgery:

An accepted preoperative bowel preparation procedure is as follows: