What Is a Colonoscopy Procedure?
A colonoscopy is a procedure to look at the inside of the colon. The colon is the large intestine and the last part of the digestive system. The colon dries, processes, and eliminates the waste left after the small intestine has absorbed the nutrients in food. The colon is about 3 to 5 feet long. It travels from the lower right corner of the abdomen (where the small intestine ends) up to the liver, across the body to the spleen in the upper left corner and then down to form the rectum and anus.
The doctor will use an instrument called the colonoscope to perform a colonoscopy. It is a long (about 5 feet), thin (about 1 inch), flexible fiberoptic camera that allows the doctor to visualize the entire colon.
A doctor may order a colonoscopy to investigate many different diseases of the colon.
Colonoscopy is best known for its use as a screening tool for the early detection of colorectal cancer.
- Colorectal cancer is the second leading cause of cancer deaths in the United States.
- Colon cancer develops from growths within the wall of the intestine such as polyps or tumors.
- These growths often take 5 to 10 years to develop and may not cause many symptoms.
- A person may not have any symptoms of colon cancer, but having a close relative with the disease increases the risk for the disease compared to the general public.
- Most people develop polyps after age 50, so the American College of Gastroenterology (the digestive specialists) recommends screening examinations every 10 years for early detection and removal of these cancer-causing growths after that age.
Colonoscopy is also used to investigate other diseases of the colon.
- Colonoscopy may be used to find the place and cause of bleeding as well as to check areas for irritation or sores in the colon.
- These colon problems can cause unexplained changes in bowel habits.
- Pain, bloody diarrhea, and weight loss can be caused by inflammation of the bowel, which may be the result of Crohn's disease or ulcerative colitis.
- These inflammatory digestive diseases tend to occur in young adults and, if undetected, can produce chronic symptoms and increase the risk of colon cancer.
Colonoscopy is used when there is concern a disease of the colon may exist.
- The doctor may recommend this test if other screening tests such as a manual rectal examination, a fecal occult blood test (a test that detects blood in the feces), or a barium enema (a test in which barium is used to make the colon visible on an X-ray) suggest that further information is needed to make a diagnosis.
- A colonoscopy may be required when symptoms of digestive disease or other warning signs are present.
- Rectal bleeding (which may appear as bright red, very dark, or black)
- Pain in the lower abdomen
- Changes in bowel habits
- Non-dietary weight loss
- A new test called Cologuard, a stool-based colorectal screening test that detects the presence of red blood cells and DNA mutations, may indicate the presence of certain kinds of abnormal growths that may be cancers such as colon cancer or precursors to cancer. If this test reveals the possibility of colon cancer, a colonoscopy may be necessary.
Only doctors who specialize in the study of digestive or rectal diseases, have special training in endoscopy, and are certified to perform colonoscopy qualify to perform this procedure.
- The American Society for Gastrointestinal Endoscopy suggests that a doctor perform at least 200 procedures to become technically competent at diagnostic colonoscopy.
Pictures of the Colon and Diseases of the Colon
Pictures of a Healthy Colon and Diseases of the Colon
Picture of the anatomy of the colon
Picture of Colon Cancer and Colon Polyps
Picture of colon cancer and colon polyps
Picture of Diverticulitis (Diverticular Disease)
Picture of Crohn's Disease
Picture of Crohn's disease
Picture of Ulcerative Colitis (UC)
What Are the Side Effects and Risks of a Colonoscopy?
As with any procedure, there are risks associated with a colonoscopy. Before obtaining your consent for the procedure, the doctor will tell you about the potential risks.
- The most common side effects are cramping pain and abdominal swelling caused by the air used to inflate the colon during the procedure. This air is expelled shortly after the procedure, and these symptoms generally resolve without medical treatment.
- If a biopsy is performed during the procedure, the patient may see small amounts of blood in the bowel movements after the examination. This may last a few days.
- Though rare, there is potential for the colonoscope to injure the intestinal wall, causing perforation, infection, or bleeding.
- Although this test is very helpful in finding the cause of many digestive diseases, abnormalities can go undetected. Factors that can affect this include the completeness of the bowel preparation before the procedure, the skill of the operator of the colonoscope, and the patient's anatomy.
- When this test is performed, the patient will be given sedating medications to make the test more comfortable. Whenever a medication is given, a risk of an allergic reaction or side effect of the medication itself is present. These IV medications are given under medical supervision, and the patient will be monitored during the procedure to lessen the risk of medication-related complications.
How Do I Prepare for a Colonoscopy? Is There a Special Diet I Need to Follow?
A colonoscopy can be performed in a hospital, clinic, or in a doctor's office, depending on the facility and situation. The patient will be given an appointment and a set of instructions to follow before the test is performed.
- Although the exact instructions given may vary from clinic to clinic, their objective is the same: to clean out the contents of the bowel before the test.
- This allows the bowel wall to be seen during the test.
- This system of cleaning the bowel is often called bowel preparation or "prep."
- The patient will be given a combination of liquid diet, laxatives, or enemas for up to two days prior to the test with instructions on how to use them. Several medications are available for bowel cleansing, including polyethylene glycol 3350 (GoLYTELY, NuLYTELY), magnesium citrate (Citroma), and senna (X-Prep).
- These medications produce diarrhea, which can be uncomfortable, but unless the bowel is empty of stool, the test can be limited and may need to be repeated at a later date.
- On the night before the test is to be performed, nothing should be taken by mouth (food or liquids) until after the test is finished.
Colon Cancer Symptoms and Signs
Colon cancer, also referred to as colorectal cancer, occurs when cancer cells form in lining of the colon or rectum. In the early stages of colon cancer there often are no symptoms. As the cancer progresses through the large intestine, symptoms and signs may begin appear, for example:
- Changes in the color of your stools
- Blood in the stools
- Weight gain
How Long Does a Colonoscopy Procedure Take?
- On the day of the colonoscopy, the patient may be asked to arrive early to prepare for the test itself, and to ask further questions. The patient will be asked the following questions:
- When did you last eat?
- What allergies do you have?
- Did you remember to take all your bowel preparation medication?
- Once the patient has changed into an examination gown, vital signs (blood pressure, heart rate, respiration rate, and temperature) will be monitored and an intravenous line (IV) will be placed to sedate the patient, and provide pain medication during the test, if necessary. Although the patient will not be fully asleep during the procedure, these medications will produce a sleepy state (sedation) and make the test more comfortable.
- The procedure will begin with the patient lying flat on the left side. The colonoscope, is lubricated to allow it to enter the anus. For a thorough investigation, air is required to gently open the folded colon. This may cause a temporary uncomfortable bloated sensation. When the doctor applies gentle pressure, the colonoscope moves further into the colon and is slowly advanced until the entire colon is seen.
- The colonoscope has a tiny camera on the end of it, which is connected to a monitor. This allows the physician to see the colon through the tip of the instrument even when it is far inside the body. As the scope passes the course of the colon, the normal turns and contours of the colon may impede the passage of the scope. The patient may be asked to change positions for better visualization. It is common for fluid and gas to escape through the rectum and anus; this should be expected. The entire procedure can take from 30 minutes up to 1 hour.
- In addition to simply viewing the bowel wall, the colonoscope has special attachments that allow the doctor to collect tissue samples or biopsies, remove small growths, and stop bleeding with laser, heat, or medication.
What Do I Do After My Colonoscopy?
You will go home later during the day after you have your colonoscopy. Colonoscopy usually is performed without checking into the hospital (as an outpatient procedure). You will be monitored and observed in the doctor's office until the side effects of the medications have worn before you can go home. The side effects of the medication may cause symptoms like nausea, bloating, and drowsiness, that may continue for some time after the procedure. You should make arrangements for someone to come and pick you up at the doctor's office and take you home because of these side effects. Recovery time after the procedure can vary. If there are no complications it can range from a few hours to a few days.
Your doctor will give you a follow-up appointment. The final results of the test are generally available at that appointment, although biopsy results may take some time. The doctor may give you specific instructions in regard to what symptoms to monitor, which ones are normal, and which are more serious. You also may receive information in regard to your diet after a colonoscopy.
Are There Alternatives to Colonoscopy?
Other tests can help a doctor detect diseases of the colon. Sometimes these tests can be done instead of a colonoscopy, but at other times they are performed in addition to a colonoscopy because each test can provide different types of information.
- With similar preparation, a special X-ray examination of the entire colon, a barium enema, can be used instead of or in addition to colonoscopy. For this test, a liquid called barium is inserted into the colon using a small tube through the anus. X-rays are then taken of the abdomen with the barium inside. This liquid is seen on the X-ray and is used to outline the irregularities of the bowel wall.
- Another test called a sigmoidoscopy can be performed. This test is very similar to a colonoscopy but requires less preparation. The instrument used, a sigmoidoscope, is 2 foot long and allows visualization of the anal canal, rectum, and the part of the colon closest to the rectum known as the sigmoid colon. Although this test is important, it does not allow detection of abnormalities in other areas of the colon because the sigmoidoscope is much shorter than the colonoscope.
- CT scans are often used to investigate abnormalities of the abdomen. Gastrografin is a liquid similar to barium, which allows the bowel to be better seen during a CT scan. This liquid, also called oral contrast, is swallowed and then allowed to pass from the stomach, through the small intestine (the ileum) and then through the large intestine (the colon) before the CT scan is performed. In this way, a CT scan can be helpful to investigate abdominal and bowel problems.
- Other tests include balloon endoscopy, push endoscopy, and virtual colonoscopy.
Your doctor will decide which of these tests is most appropriate for you.
When to Seek Medical Care for Colonoscopy Complications
Call a doctor if any unexpected symptoms occur, including:
- Persistent nausea
- Persistent but minor bleeding
- Ongoing bloating and abdominal discomfort
If there are additional concerns, call the doctor's office for advice and evaluation.
Minor symptoms, such as bloating, are common after this procedure. More serious symptoms should prompt the patient to seek urgent medical attention. Call your physician and go directly to the emergency department if the patient experiences any of the following:
Reviewed on 9/11/2017
FDA. FDA approves first non-invasive DNA screening test for colorectal cancer.
American Society for Gastrointestinal. "Understanding Colonoscopy." 2017.
CDC. "Colorectal Cancer Statistics." Updated:
Jun 07, 2017.
Lewis, JR, et al. Update on Colonoscopy Preparation, Premedication and Sedation." Medscape. Updated: 2013.