Colonoscopy and virtual colonoscopy

ALSO KNOWN AS: Endoscopy, CT colonoscopy

DEFINITION: These procedures employ either a colonoscope (a flexible tube inserted into the colon with a light and camera at the tip) or computerized imaging to examine the large intestine for precancerous, cancerous, and other conditions.

Cancers diagnosed: Cancers of the large intestine and rectum, precancerous adenomas, polyps

Why performed: These procedures are intended to prevent and detect colon cancer in people over fifty years of age or earlier when indicated. They are also a necessary component in managing inflammatory bowel diseases (Crohn's disease and ulcerative colitis) or for individuals with a family history of polyps or diseases of the large intestine. The American Cancer Society advises everyone at average risk of colorectal cancer to begin screenings at age forty-five using a stool-based test or a visual exam and continue these screenings through at least age seventy-five. Individuals at increased risk include those with a history of belly or pelvic area radiation for cancers, inflammatory bowel disease, certain polyps, or colorectal cancers. Risk also increases for individuals with a family history of hereditary colorectal cancer syndrome, familial adenomatous polyposis (FAP), Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC), or colon cancer.

Many patients resist the procedure as a result of embarrassment or concern over the bowel preparation, which is the same for traditional and virtual colonoscopy. Neither procedure replaces the need for yearly testing for blood in the feces with a guaiac-based fecal occult blood test (gFOBT) or a fecal immunochemical test (FIT). There are several considerations in deciding on the appropriate procedure. Patients should discuss family history of any bowel disease, increasing age, existing medical problems, and other personal issues with a physician when deciding the most appropriate procedure. Both forms of colonoscopy are considered the most thorough and accurate in examining the entire large intestine. Still, there are differences in how they are performed and what happens if a test is abnormal.

Patient preparation: Patients should not stop taking medications (such as insulin, aspirin, or blood thinners) to prepare for a colonoscopy unless their physicians approve. Three days before either procedure, the patient should stop eating a high-fiber diet or taking fiber supplements, iron-containing vitamins, or iron tablets. The day before the procedure, all three meals should only contain clear liquids, such as tea, broth, gelatin, clear juices, tea, or coffee.

The doctor will provide bowel preparation information and laxatives, either tablets or liquid, to take the day before the procedure and possibly again a few hours before the procedure. The large intestine must be empty and free of all fecal matter to see any abnormal growths or changes in the wall of the intestine. The patient may not eat or drink anything after midnight before the procedure unless it is water to take approved medication.

Steps of the procedure: Traditional colonoscopy is usually performed in an outpatient surgery suite. Patients are moderately sedated and given pain medication through an intravenous catheter. It is common for patients to sleep through the procedure, which can take thirty to sixty minutes.

The patient lies on the left side, and a colonoscope is inserted through the anus and rectum. The doctor watches a video screen as the tube is guided through the large intestine. The examination includes visualization during the slow withdrawal of the tube, as some growths can be hidden in folds in the intestine. The gastroenterologist is looking at the actual lining of the intestine, not a computerized image.

During this procedure, healthcare professionals can remove polyps, sample abnormal tissue (biopsy), remove small growths, stop small areas of bleeding, laser treat abnormal tissue or growths, and introduce certain medicines. A radiologist performs a virtual colonoscopy in a radiology suite with no sedation. The patient lies on their back on a table, and a thin tube is inserted into their rectum, introducing air to inflate the large intestine for better visualization. The table passes through the scanner as three-dimensional computerized images of the large intestine are made and immediately viewed on a video screen. The patient must periodically hold their breath to ensure clear and precise imaging.

The procedure is repeated with the patient lying on their stomach and is complete in ten to fifteen minutes. If anything abnormal is identified, a traditional colonoscopy might be required. If the procedure cannot be performed on the same day, repeat bowel preparation will be necessary.

After the procedure: The patient must be driven home after a traditional colonoscopy, as the sedation used during the procedure makes driving unsafe. It can take one to two hours for the patient to be alert enough to be driven home. There can be some abdominal cramping and feelings of gas. Patients can resume normal activities the following day.

Virtual colonoscopy does not require medication, and patients can leave immediately after the procedure. Some cramping might occur following virtual colonoscopy because of the introduction of air during the procedure.

Risks: Though rare, perforation and large intestine infection are possible complications from traditional colonoscopy. The doctor will provide an information sheet that describes what is normal and not normal following a colonoscopy. Symptoms that should indicate calling the doctor include bloody diarrhea, blood coming from the rectum, dizziness, fever, severe abdominal pain, and weakness. There is radiation exposure with virtual colonoscopy.

Results: Both procedures are considered the most thorough in examining the large intestine. Traditional colonoscopy is better at finding growths smaller than ten millimeter. It has the advantage of permitting biopsies of abnormal growths, removal of polyps, treatment of inflammation or disease, and laser treatment during the examination. Virtual colonoscopy has been widely embraced by those fearful of traditional colonoscopy. Traditional colonoscopy is required following virtual colonoscopy if any abnormalities are found. Some studies have found that specific abnormalities in virtual colonoscopy were normal when traditional colonoscopy followed. Studies continue to compare the benefits and drawbacks of each procedure.

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