What does colonoscopy mean?
An examiner is enabled by a Colonoscopy procedure (usually a gastroenterologist) to evaluate the inside of the colon (large intestine or large bowel). The colonoscope is a four foot long, flexible tube about the thickness of a finger with a camera and a source of light at its tip. The tip of the colonoscope is inserted into the anus and then is advanced slowly, under visual control, into the rectum and through the colon usually as far as the cecum, which is the first part of the colon.
What is the importance of colonoscopy?
Colonoscopy may be done for a variety of reasons. It is done to investigate:
- the cause of blood in the stool,
- abdominal pain,
- a change in bowel habit, or
- an abnormality found on colonic X-rays or a computerized tomographic (CT) scan
Individuals with previous history of polyps or colon cancer and certain individuals with a family history of some types of non-colonic cancers or colonic problems that may be associated with colon cancer (such as ulcerative colitis and colonic polyps) may be advised to have periodic colonoscopies because their risks are greater for polyps or colon cancer. How often should one undergo colonoscopy depends on the degree of the risks and the abnormalities found at previous colonoscopies. In recent days, it has been recommended that even healthy people at normal risk for colon cancer should undergo colonoscopy at age 50 and every 11 years thereafter, for the purpose of removing colonic polyps before they become cancerous.
What bowel preparation is needed for colonoscopy?
If the procedure is to complete and maintain accuracy, the colon must be completely cleaned, and there are several colonoscopy preparations. Patients are given detailed instructions about the cleansing preparation. In general, this consists of drinking a large volume of a special cleansing solution or several days of a clear liquid diet and laxatives or enemas prior to the examination. These instructions should be followed exactly as prescribed or the procedure may be unsatisfactory, and may have to be repeated, or a less accurate alternative test may be performed in its place.
What about current medications or diet before colonoscopy?
Most medications should be continued as usual, but some may interfere with the examination. It is best that the physician is informed of all current prescriptions or over-the-counter medications. Aspirin products, blood thinners (warfarin [Coumadin], etc.), arthritis medications, insulin, and iron preparations are examples of medications that may require special instructions. The colonoscopist will also want to be aware of a patient's allergies and any other major illnesses. The colonoscopist should be alerted if, in the past, patients have required antibiotics prior to surgical or dental procedures to prevent infections. Instructions may also be given to avoid certain foods for a couple of days prior to the procedure, such as stringy foods and foods with seeds.
What should a patient expect during colonoscopy?
Prior to colonoscopy, intravenous fluids are started, and the patient is placed on a monitor for continuous monitoring of heart rhythm and blood pressure as well as oxygen in the blood. Medications (sedatives) usually are given through an intravenous line so the patient becomes sleepy and relaxed, and to reduce pain. If needed, the patient may receive additional doses of medication during the procedure. Colonoscopy often produces a feeling of pressure, cramping, and bloating in the abdomen; however, with the aid of medications, it is generally well-tolerated and infrequently causes severe pain.
Patients will lie on their left side or back as the colonoscope is slowly advanced. Once the tip of the colon (cecum) or the last portion of the small intestine (terminal ileum) is reached, the colonoscope is slowly withdrawn, and the lining of the colon is carefully examined. Colonoscopy usually takes 15 to 60 minutes. If the entire colon, for some reason, cannot be visualized, the physician may decide to try colonoscopy again at a later date with or without a different bowel preparation or may decide to order an X-ray or CT of the colon.
What if there are abnormalities detected during colonoscopy?
If an abnormal area needs to be better evaluated, a biopsy forceps is passed through a channel in the colonoscope and a biopsy (a sample of the tissue) is obtained. The biopsy is submitted to the pathology laboratory for examination under a microscope by a pathologist. If infection is suspected, a biopsy may be obtained for culturing of bacteria (and occasionally viruses) or examination under the microscope for parasites. If colonoscopy is performed because of bleeding, the site of bleeding can be identified, samples of tissue obtained (if necessary), and the bleeding controlled by several means. Should there be polyps, (benign growths that can become cancerous) they almost always can be removed through the colonoscope. An important method of preventing colorectal cancer is the removal of these polyps, although the great majority of polyps are benign. None of these additional procedures typically produce pain. Biopsies are taken for many reasons and do not necessarily mean that cancer is suspected.
What should a patient expect post colonoscopy?
Patients will be kept in an observation area for an hour or two post-colonoscopy, until the effects of medications that have been given adequately wear off. If patients have been given sedatives before or during colonoscopy, they may not drive, even if they feel alert. Someone else must drive them home. The patient's reflexes and judgement may be impaired for the rest of the day, making it unsafe to drive, operate machinery, or make important decisions. Should patients have some cramping or bloating, this can be relieved quickly with the passage of gas, and they should be able to eat upon returning home. After the removal of polyps or certain other manipulations, the diet or activities of patients may be restricted for a brief period of time.
Prior to the patient's departure from the colonoscopic unit, the findings can be discussed with the patient. However, at times, a definitive diagnosis may have to wait for a microscopic analysis of biopsy specimens, which usually takes a few days.
What are the possible complications or alternatives to colonoscopy?
Complications of colonoscopy are rare and usually minor when performed by physicians who have been specially trained and are experienced.
Bleeding may occur at the site of biopsy or removal of polyps, but the bleeding is usually minor and self-limited or can be controlled through the colonoscope. It is quite unusual to require transfusions or surgery for post-colonoscopic bleeding. An even less common complication is a perforation or a tear through the colonic wall, but even these perforations do not usually require surgery.
Other potential complications are reactions to the sedatives used, localized irritation to the vein where medications were injected (leaving a tender lump lasting a number of days, which goes away eventually), or complications from existing heart or lung disease. The incidence of all of these, together, is less than one percent.
While these complications are rare, it is important for patients to recognize early signs of a complication so that they may return to their physicians or an emergency room. The colonoscopist who performed the colonoscopy should be contacted if patients notice severe abdominal pain, rectal bleeding of more than half a cup, or fever and chills.
Colonoscopy is the best method available to detect, diagnose, and treat abnormalities within the colon. The alternatives to colonoscopy are quite limited. Barium enema is a less accurate test performed with X-rays. It misses abnormalities more often than colonoscopy, and, if an abnormality is found, a colonoscopy may still be required to biopsy or remove the abnormality. At times, an abnormality or lesion detected with a barium enema is actually stool or residual food in a poorly cleansed colon. Colonoscopy may then be necessary to clarify the issue. Flexible sigmoidoscopy is a limited examination that uses a shorter colonoscope and examines only the last one-third of the colon.
What is virtual colonoscopy?
Another alternative to colonoscopy is virtual colonoscopy. Virtual colonoscopy is a technique that uses computerized tomography (CT) scanning to obtain images of the colon that are similar to the views of the colon obtained by direct observation through colonoscopy. The images are constructed using the CT images so they do not represent true images. They are virtual images.
In preparation for virtual colonoscopy, the day before the examination, the colon is cleaned-out using laxatives. During the examination a tube is inserted into the anus and is used to inject air into the colon. The CT scans are then performed with the colon inflated, and the scans are analyzed and manipulated to form a virtual image of the colon. When properly performed, virtual colonoscopy can be effective. It can even find polyps "hiding" behind folds that occasionally are missed by colonoscopy.
Nevertheless, virtual colonoscopy has several limitations:
- Virtual colonoscopy exposes individuals to a moderate amount of radiation.
- Virtual colonoscopy has difficulty identifying small polyps (less than 5 mm in size) that are easily seen at colonoscopy.
- Virtual colonoscopy does not allow the use of the newer techniques that are being developed to differentiate between abnormal lesions that need to be biopsied or removed and those that don't.
- Virtual colonoscopy has great difficulty identifying flat cancers or premalignant lesions that are not protruding, that is, are not polyp-like.
- Virtual colonoscopy does not allow removal of polyps that are found. Thirty to forty percent of people have colon polyps. If polyps are found by virtual colonoscopy, then colonoscopy must be done to remove the polyps. Therefore, many individuals having virtual colonoscopy will have to undergo a second procedure, colonoscopy.
Because of these limitations, virtual colonoscopy has not replaced colonoscopy as the primary screening tool for individuals at increased risk for polyps or colon cancer. It is currently an option for individuals at normal risk for polyps and colon cancer who cannot or will not undergo colonoscopy.