COLONOSCOPY
Colonoscopy is an endoscopic technique that allows internal inspection of the entire colorectal tract (see Figure 2).3 Although the most invasive of the exams being reviewed (and requiring extensive bowel prep), it is the gold standard for CRC screening.3
Current literature indicates that colonoscopy should be the screening method of choice for patients who have symptoms of colorectal cancer, positive results with an indirect screening exam such as FOBT, or who fall within a high-risk category. Persons at high risk for CRC include those with a significant family history, persons ages 50 and older, African Americans, and persons with an intestinal inflammatory condition, diabetes mellitus, obesity, sedentary lifestyle, positive smoking status, and low-fiber/high-fat diet.
Procedure
This procedure is performed on an outpatient basis; bowel prep is required one day prior to the procedure so that the bowel movements are clear of fecal matter. The patient receives short-lasting sedation, such as midazolam, via an IV line prior to being brought into the exam room. The procedure itself can take up to 30 minutes, with the patient comfortably sedated in an oblique position. The patient is allowed to recover for several hours, or until awake and able to pass flatus.
Patient Experience
The patient may experience discomfort during the bowel prep phase, as with BE preparation. The patient may be uncomfortable during insertion and manipulation of the colonoscope and also with gaseous insufflation that is used to improve visualization.
Advantages and Disadvantages
The advantages of colonoscopy over the other direct methods are the ability to immediately remove early cancer and colonic polyps and the ability to obtain histologic samples. A suspicious mass can be biopsied during the procedure and, depending on the size, may be completely excised. The histology of the biopsied tissue samples can aid in determining need for further treatment or establish an appropriate surveillance interval for the patient.3
The disadvantages of colonoscopy are related to the possible complications of the procedure, including colon perforation and postpolypectomy bleeding. The risk for these events is estimated to be between 0.1% and 0.3%.3 In addition, the short-lasting sedation that is used during the procedure poses the risk for possible respiratory collapse.6 Therefore, each patient requires medical clearance prior to administering sedation. The risk for a serious adverse event is 3 to 5 per 1,000 colonoscopies, and procedure-related mortality, while rare, has been reported.2,4,14
Limitations
Studies have found colonoscopy to be the most expensive of the direct screening tests, which may pose a problem for uninsured or underinsured patients.4,14
A collection of colonoscopy studies done on patients ages 50 to 66 showed an adenoma miss rate of 20% to 26% for any adenoma < 10 mm, and a 2.1% miss rate for adenomas ≥ 10 mm.3 Adenoma detection rates are dependent on optimal bowel preparation, complete examination of the colon, and the time the clinician spends examining all surfaces of the colon mucosa when withdrawing the colonoscope.3
Colonoscopy has the lowest adherence rate of all the CRC screening tests, which is not surprising since it is invasive, involves sedation, and requires thorough preparation. However, colonoscopies may be performed at longer intervals (up to 10 years) compared to other screening tests; the risk for developing CRC after a negative colonoscopy exam remains low.3
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