Chapter 38B

Colon tumors remain one of the more common reasons for abdominal surgery. Adenocarcinoma of the colon is still the most common histology requiring operative intervention. Other types of malignant tumors and benign lesions make up a distinct minority of colonic neoplastic indications for operation.

The etiology of colorectal cancer remains elusive. Dietary factors, including macro- and micronutrients, have maintained a central importance in theories of the etiology of colon cancer. High dietary fiber, once felt to be protective, has more recently been demonstrated in a large prospective study to not prevent colorectal cancer.1 Conversely, the breakdown products of cooked meat have clearly been implicated in the development of colorectal cancer.2 Because rigid control of the constituents of diet over time is highly unlikely and even strict vegetarians have developed colorectal cancer, it is not likely that lifelong dietary manipulation will substantially alter the natural history of this disease.

Screening for colorectal cancer is clearly effective in reducing the overall mortality from colorectal cancer, presumably by discovery of tumors at an earlier and thus more curable stage. In this respect, it is an ideal disease for directed screening, because the precancerous phase is long and removal of the precancerous lesion is preventive of cancer. The incidence of colorectal cancer has been in a slow decline over the past 10–15 years, due in part to increased application of screening programs in the population as a whole.3

Because of noncompliance of the American population with Hemoccult testing programs or, in fact, any other procedures that require interacting with stool (such as stool DNA analysis), intermittent anatomic evaluation of the entire colon and rectum by some means has become the preferred manner of colorectal cancer screening. Practically, total colonoscopy has become the most common screening procedure, beginning at age 50 in normal-risk individuals. Alternatively, flexible sigmoidoscopy and air contrast barium enema are recommended at 5-year intervals; they are perceived by patients and primary care physicians to be more uncomfortable because of the lack of conscious sedation when compared to colonoscopy.

Radiographic screening with three-dimensional software for interpretation of cross-sectional images is popularly known as “virtual colonoscopy,” a misnomer leading to misunderstandings about the procedure. Individuals undergoing computed tomographic (CT) colonography must mechanically cleanse the colon and then have air (or carbon dioxide) insufflation prior to imaging. Positive findings necessitate referral for optical colonoscopy. There are certain circumstances in which diagnostic CT imaging is indicated; comorbidities that preclude conscious sedation, refusal on the part of the patient to undergo colonoscopy or prior failed attempt(s) and obstruction preventing proximal passage of the instrument are all reasonable indications for CT colonography.

It must be stressed that no method of screening is infallible. Furthermore, there are some individuals who do not have any identifiable factors that would indicate surveillance at an earlier age or with greater frequency who develop colorectal cancer.

Among identifiable risk ...

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