Endoscopy vs. colonoscopy: What's the difference?

Sometimes endoscopes are cameras on long tubes, but in recent years technology has allowed doctors to mount cameras in small pills to reduce the risk of complications and unpleasantness.
Sometimes endoscopes are cameras on long tubes, but in recent years technology has allowed doctors to mount cameras in small pills to reduce the risk of complications and unpleasantness.

Both endoscopy and colonoscopy are nonsurgical procedures that involve use of a flexible tube with a light and camera to examine parts of the digestive tract. A colonoscopy is a type of endoscopy.

The term “endoscopy” often refers to an upper endoscopy (sometimes called a gastroscopy), a procedure in which an endoscope (a long flexible tube with a camera attached on the end) is passed through the mouth and throat into the esophagus, so a doctor can visualize the esophagus, stomach, and upper part of the small intestine (duodenum).

In an ultrasound endoscopy, a small ultrasound device is installed on the tip of the endoscope, which allows doctors to get more accurate and detailed images than those obtained from external ultrasounds.

There is generally no specific preparation required for an upper endoscopy, but doctors generally prefer your stomach be empty.

When an endoscope is passed through the rectum into the large intestine (colon), the procedure is called a sigmoidoscopy or colonoscopy, depending on how much of the colon is examined.

An endoscopy or a colonoscopy usually can be done in 10-30 min, unless there are complications or further investigations with biopsies, or polyp removal is necessary.

A colonoscopy requires preparation to clear out the colon. Most colonoscopy preparations involve drinking large amounts of cleansing solutions (such as MiraLAX), along with laxatives, enemas, and possibly several days of a clear liquid diet prior to the procedure

What is the preparation for endoscopy vs. colonoscopy?

Endoscopy

To accomplish a safe and complete examination, the stomach should be empty. The patient will most likely be asked to have nothing to eat or drink for six hours or more prior to the procedure.

Prior to scheduling the procedure, the patient should inform his or her physician of any medications being taken, any allergies, and all known health problems. This information will help the doctor determine whether the patient may need antibiotics prior to the procedure, and what potential medications should not be used during the exam because of the patient's allergies. The information will provide the individual scheduling the procedure an opportunity to instruct the patient whether any of the medications should be held or adjusted prior to the endoscopy.

Knowledge that the patient has any major health problems, such as heart or lung diseases, will alert the doctor of possible need for special attention during the procedure.

Colonoscopy

If the procedure is to be complete and accurate, the colon must be completely cleaned, and there are several different 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 (visualization of the lining of the colon may be obscured by residual stool), and it may have to be repeated, or a less accurate alternative test must be performed in its place.

Instructions may also be given to avoid certain foods for a couple of days prior to the procedure, such as stringy foods, foods with seeds, or red Jell-O.

Most medications should be continued as usual, but some may interfere with the examination. It is best if the colonoscopist is informed of all current prescription and over-the-counter medications. Aspirin products, blood thinners such as warfarin (Coumadin), 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.

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What happens during the endoscopy and colonoscopy procedures?

Endoscopy

Before the procedure, the doctor will discuss with you why the procedure is being done, whether there are alternative procedures or tests, and what possible complications may result from the endoscopy.

Practices vary amongst doctors, but the patient may have the throat sprayed with a numbing solution and will probably be given sedating and pain alleviating medications through a vein. You will be relaxed after receiving this medication, usually midazolam (Versed) for sedation and fentanyl for pain relief, and you may even go to sleep. This form of sedation is called conscious sedation, and usually is administered by a nurse who monitors you during the entire procedure.

You also may be sedated using propofol (Diprivan) called "deep sedation," which usually is administered by a nurse anesthetist or anesthesiologist who monitors your vital signs (blood pressure and pulse) as well as the amount of oxygen in your blood during the procedure.

After you are sedated while lying on your left side the flexible video endoscope, the thickness of a small finger, is passed through the mouth into the esophagus, stomach, and duodenum. This procedure will NOT interfere with your breathing. Most people experience only minimal discomfort during the test, and many sleep throughout the entire procedure using conscious sedation. Deep sedation ensures that you feel no discomfort during the entire procedure.

Afterwards, you’ll go to a rest area in the hospital or medical center to let the medication wear off. You must have someone drive you home as the sedation medication makes it unsafe to operate heavy machinery.

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.

If an abnormal area needs to be better evaluated, a biopsy forceps can be passed through a channel in the colonoscope and a biopsy (a sample of the tissue) can be 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 fungus) 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. Removal of these polyps is an important method of preventing colon and rectal cancer, although the great majority of polyps are benign and do not become cancerous. None of these additional procedures typically produces pain. Biopsies are taken for many reasons and do not necessarily mean that cancer is suspected.

What are the risks of colonoscopy and endoscopy?

Endoscopy

Endoscopy is a safe procedure and when performed by a physician with specialized training in these procedures, the complications are extremely rare. They may include localized irritation of the vein where the medication was administered, reaction to the medication or sedatives used, complications from pre-existing heart, lung, or liver disease, bleeding may occur at the site of a biopsy or removal of a polyp (which if it occurs is almost always minor and rarely requires transfusions or surgery). Major complications such as perforation (punching a hole through the esophagus, stomach, or duodenum) are rare but usually require surgical repair.

Colonoscopy

Complications of colonoscopy are rare and usually minor when performed by physicians who have been specially trained and are experienced in colonoscopy.

Bleeding may occur at the site of biopsy or removal of polyps, but the bleeding usually is 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 may not 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 day or two), or complications from existing heart or lung disease. The incidence of all of these complications together is less than 1%.

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 a patient notices 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 still may 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 nature of the lesion. Flexible sigmoidoscopy is a limited examination that uses a shorter colonoscope and examines only the last one-third of the colon.

Patients will be kept in an observation area for an hour or two post-colonoscopy until the effects of medications that have been given wear off. If patients have been given sedatives before or during colonoscopy, they may not drive, even if they feel alert. 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.

When will I get the results for an endoscopy vs. colonoscopy?

Endoscopy

Under most circumstances, the examining physician will inform the patient of the test results or the probable findings prior to discharge from the recovery area. The results of biopsies or cytology usually take 72-96 hours and the doctor may only give the patient a presumptive diagnosis pending the definitive one, after the microscopic examination of the biopsies.

Colonoscopy

Prior to the patient's departure from the coloscopic 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.

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Medically Reviewed on 1/27/2020
References
Yusuf, T, MD, et al. Esophagogastroduodenoscopy. Medscape. Updated: May 24, 2018.

UpToDate. Patient information: Colonoscopy (Beyond the Basics).
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