During a colonoscopy, the doctor inserts a colonoscope into your rectum to check for abnormalities in your entire colon.
A colonoscopy (koe-lun-OS-kuh-pee) is an exam used to look for changes — such as swollen, irritated tissues, polyps or cancer — in the large intestine (colon) and rectum.
During a colonoscopy, a long, flexible tube (colonoscope) is inserted into the rectum. A tiny video camera at the tip of the tube allows the doctor to view the inside of the entire colon.
If necessary, polyps or other types of abnormal tissue can be removed through the scope during a colonoscopy. Tissue samples (biopsies) can be taken during a colonoscopy as well.
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Why it's done
Your doctor may recommend a colonoscopy to:
- Investigate intestinal signs and symptoms. A colonoscopy can help your doctor explore possible causes of abdominal pain, rectal bleeding, chronic diarrhea and other intestinal problems.
- Screen for colon cancer. If you're age 45 or older and at average risk of colon cancer — you have no colon cancer risk factors other than age — your doctor may recommend a colonoscopy every 10 years. If you have other risk factors, your doctor may recommend a screen sooner. Colonoscopy is one of a few options for colon cancer screening. Talk with your doctor about the best options for you.
- Look for more polyps. If you have had polyps before, your doctor may recommend a follow-up colonoscopy to look for and remove any additional polyps. This is done to reduce your risk of colon cancer.
- Treat an issue. Sometimes, a colonoscopy may be done for treatment purposes, such as placing a stent or removing an object in your colon.
- Splitting doses for colonoscopy preparation
- Anal itching
- Carcinoid tumors
- Colon cancer
- Colon polyps
- Constipation in children
- Crohn's disease
- Inflammatory bowel disease (IBD)
- Intestinal ischemia
- Iron deficiency anemia
- Irritable bowel syndrome
- Ischemic colitis
- Pseudomembranous colitis
- Rectal cancer
- Rectovaginal fistula
- Ulcerative colitis
- Mayo Clinic Minute: What you need to know about polyps in your colon
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A colonoscopy poses few risks. Rarely, complications of a colonoscopy may include:
- A reaction to the sedative used during the exam
- Bleeding from the site where a tissue sample (biopsy) was taken or a polyp or other abnormal tissue was removed
- A tear in the colon or rectum wall (perforation)
After discussing the risks of colonoscopy with you, your doctor will ask you to sign a consent form giving permission for the procedure.
How you prepare
Before a colonoscopy, you'll need to clean out (empty) your colon. Any residue in your colon may make it difficult to get a good view of your colon and rectum during the exam.
To empty your colon, your doctor may ask you to:
- Follow a special diet the day before the exam. Typically, you won't be able to eat solid food the day before the exam. Drinks may be limited to clear liquids — plain water, tea and coffee without milk or cream, broth, and carbonated beverages. Avoid red liquids, which can be mistaken for blood during the colonoscopy. You may not be able to eat or drink anything after midnight the night before the exam.
- Take a laxative. Your doctor will usually recommend taking a prescription laxative, usually in a large volume in either pill form or liquid form. In most instances, you will be instructed to take the laxative the night before your colonoscopy, or you may be asked to use the laxative both the night before and the morning of the procedure.
Adjust your medications. Remind your doctor of your medications at least a week before the exam — especially if you have diabetes, high blood pressure or heart problems or if you take medications or supplements that contain iron.
Also tell your doctor if you take aspirin or other medications that thin the blood, such as warfarin (Coumadin, Jantoven); newer anticoagulants, such as dabigatran (Pradaxa) or rivaroxaban (Xarelto), used to reduce risk of blot clots or stroke; or heart medications that affect platelets, such as clopidogrel (Plavix).
You may need to adjust your dosages or stop taking the medications temporarily.
What you can expect
During the procedure
During a colonoscopy, you'll wear a gown, but likely nothing else. Sedation or anesthesia is usually recommended. In most cases, the sedative is combined with pain medication given directly into your blood stream (intravenously) to lessen any discomfort.
You'll begin the exam lying on your side on the exam table, usually with your knees drawn toward your chest. The doctor will insert a colonoscope into your rectum.
The scope — which is long enough to reach the entire length of your colon — contains a light and a tube (channel) that allows the doctor to pump air, carbon dioxide or water into your colon. The air or carbon dioxide inflates the colon, which provides a better view of the lining of the colon.
When the scope is moved or air is introduced, you may feel stomach cramping or the urge to have a bowel movement.
The colonoscope also contains a tiny video camera at its tip. The camera sends images to an external monitor so that the doctor can study the inside of your colon.
The doctor can also insert instruments through the channel to take tissue samples (biopsies) or remove polyps or other areas of abnormal tissue.
A colonoscopy typically takes about 30 to 60 minutes.
After the procedure
After the exam, it takes about an hour to begin to recover from the sedative. You'll need someone to take you home because it can take up to a day for the full effects of the sedative to wear off. Don't drive or make important decisions or go back to work for the rest of the day.
You may feel bloated or pass gas for a few hours after the exam, as you clear the air from your colon. Walking may help relieve any discomfort.
You may also notice a small amount of blood with your first bowel movement after the exam. Usually this isn't cause for alarm. Consult your doctor if you continue to pass blood or blood clots or if you have persistent abdominal pain or a fever. While unlikely, this may occur immediately or in the first few days after the procedure, but may be delayed for up to 1 to 2 weeks.
A colonoscopic examination involves gently inserting a fiber-optic colonoscope into your rectum and large intestine to view your lower gastrointestinal tract.
Your doctor will review the results of the colonoscopy and then share the results with you.
A colonoscopy is considered negative if the doctor doesn't find any abnormalities in the colon.
Your doctor may recommend that you have another colonoscopy:
- In 10 years, if you're at average risk of colon cancer and you have no colon cancer risk factors other than age or if you have benign small polyps.
- In 1 to 7 years, depending on a variety of factors: The number, size and type of polyps removed; if you have a history of polyps in previous colonoscopy procedures; if you have certain genetic syndromes; or if you have a family history of colon cancer.
If there was residual stool in the colon that prevented complete examination of your colon, your doctor may recommend a repeat colonoscopy. How soon will depend on the amount of stool and how much of your colon was able to be seen. Your doctor may recommend a different bowel preparation to ensure that your bowel is completely emptied before the next colonoscopy.
A colonoscopy is considered positive if the doctor finds any polyps or abnormal tissue in the colon.
Most polyps aren't cancerous, but some can be precancerous. Polyps removed during colonoscopy are sent to a laboratory for analysis to determine whether they are cancerous, precancerous or noncancerous.
Depending on the size and number of polyps, you may need to follow a more rigorous surveillance schedule in the future to look for more polyps.
If your doctor finds one or two polyps less than 0.4 inch (1 centimeter) in diameter, he or she may recommend a repeat colonoscopy in 7 to 10 years, depending on your other risk factors for colon cancer.
Your doctor will recommend another colonoscopy sooner if you have:
- More than two polyps
- A large polyp — larger than 0.4 inch (1 centimeter)
- Polyps and also residual stool in the colon that prevents complete examination of the colon
- Polyps with certain cell characteristics that indicate a higher risk of future cancer
- Cancerous polyps
If you have a polyp or other abnormal tissue that couldn't be removed during the colonoscopy, your doctor may recommend a repeat exam with a gastroenterologist who has special expertise in removing large polyps, or surgery.
Problems with your exam
If your doctor is concerned about the quality of the view through the scope, he or she may recommend a repeat colonoscopy or a shorter time until your next colonoscopy. If your doctor was unable to advance the scope through your entire colon, a virtual colonoscopy may be recommended to examine the rest of your colon.
Explore Mayo Clinic studies of tests and procedures to help prevent, detect, treat or manage conditions.
By Mayo Clinic Staff
How accurate is stool test for colon cancer? ›
FIT: The fecal immunochemical test, or FIT, uses antibodies to detect blood in the stool, and it's about 79% accurate at detecting colon cancer. All you have to do: Have a bowel movement, collect a small amount of fecal matter and send it to the lab for analysis.Can a doctor tell if polyp is cancerous during colonoscopy? ›
Most polyps are benign (not cancerous). Your doctor can tell if a colon polyp is cancerous during a colonoscopy by collecting tissue to biopsy. The results of the biopsy are typically sent to your doctor within a week. Only 5% to 10% of all polyps become cancerous.How often to have colonoscopy if polyps found? ›
If your doctor finds one or two polyps less than 0.4 inch (1 centimeter) in diameter, he or she may recommend a repeat colonoscopy in 7 to 10 years, depending on your other risk factors for colon cancer. Your doctor will recommend another colonoscopy sooner if you have: More than two polyps.Is the second round of colonoscopy prep easier? ›
Yes. We recommend taking the second dose of super bowel prep because it helps us clean the part of the colon where we can easily see flat polyps.What is the best test to detect colon cancer? ›
- Colonoscopy is one of the most sensitive tests currently available for colon cancer screening.
- The doctor can view your entire colon and rectum.
- Abnormal tissue, such as polyps, and tissue samples (biopsies) can be removed through the scope during the exam.
- Stool tests. Both polyps and colorectal cancers can bleed, and stool tests check for tiny amounts of blood in feces (stool) that cannot be seen visually. ...
- Sigmoidoscopy. ...
- Colonoscopy. ...
- Other methods.
Most colon polyps are harmless. But over time, some colon polyps can develop into colon cancer, which may be fatal when found in its later stages. Anyone can develop colon polyps.What is the main cause of colon polyps? ›
A polyp is the result of genetic changes in the cells of the colon lining that affect the normal cell life cycle. Many factors can increase the risk or rate of these changes. Factors are related to your diet, lifestyle, older age, gender and genetics or hereditary issues.What symptoms do bowel polyps cause? ›
But some larger polyps can cause:
- a small amount of slime (mucus) or blood in your poo (rectal bleeding)
- diarrhoea or constipation.
- pain in your tummy (abdominal pain)
Research suggests that eating less of the following foods may have health benefits and may lower your chances of developing polyps: fatty foods, such as fried foods. red meat, such as beef and pork. processed meat, such as bacon, sausage, hot dogs, and lunch meats.
What percentage of polyps removed from colon are cancerous? ›
Only a small percentage of polyps (3.4%) were cancerous.How many years does it take for a colon polyp to become cancerous? ›
It takes approximately 10 years for a small polyp to develop into cancer. Family history and genetics — Polyps and colon cancer tend to run in families, suggesting that genetic factors are important in their development.Is morning or afternoon better for colonoscopy? ›
Colonoscopies performed in the afternoon (PM) have been shown to have lower adenoma detection rates (ADR) compared to those in the morning (AM). Endoscopist fatigue has been suggested as a possible reason.Is it better to sip or chug colonoscopy prep? ›
“If you sip it, you're never going to finish,” says Dr. Hui. “Just chug it.” Modify your diet in the days leading up to your colonoscopy prep.Will I be up all night with colonoscopy prep? ›
Will I be up all night with colonoscopy prep? Probably not, if you start on time. While everyone's body is different, most people are able to complete their round of purging before going to sleep for the night.What was your first colon cancer symptoms? ›
Signs and symptoms of colon cancer include: A persistent change in your bowel habits, including diarrhea or constipation or a change in the consistency of your stool. Rectal bleeding or blood in your stool. Persistent abdominal discomfort, such as cramps, gas or pain.What are the early warning signs of bowel cancer? ›
The 3 main symptoms of bowel cancer are blood in the stools (faeces), a change in bowel habit, such as more frequent, looser stools, and abdominal (tummy) pain. However, these symptoms are very common.Where does colon cancer usually start? ›
Almost all colon cancers start in the lining of the colon and rectum. When doctors talk about colorectal cancer, this is usually what they are talking about. There is no single cause of colon cancer. Nearly all colon cancers begin as noncancerous (benign) polyps, which slowly develop into cancer.What is the gold standard for colon cancer screening? ›
Your Colorectal Cancer Screening Choices
The gold standard for screening, a colonoscopy, only needs to be done once every 10 years for people at average risk if no precancerous changes are found.
A colonoscopy is the only test that allows your doctor to find and remove polyps during the same exam. That means removal of abnormal tissue before it grows into cancer.
How do you check for colon cancer without a colonoscopy? ›
Stool based tests, such as Cologuard or FIT, are reasonable alternatives for patients who are unable or unwilling to undergo a standard colonoscopy. Screening saves lives. Talk to your doctor about the appropriate colon cancer screening option for you.Do most people have polyps during colonoscopy? ›
Here's what we know: As often as 40% of the time, a precancerous polyp — frequently a type called an adenoma — is found during a screening colonoscopy. Colon cancer is found during only in about 40 out of 10,000 screening colonoscopies, Dr. Sand said.Do a lot of people have colon polyps? ›
Colon polyps are common in American adults. Anywhere between 15 and 40 percent of adults may have colon polyps. Colon polyps are more common in men and older adults.Can anxiety cause colon polyps? ›
These stress related factors may influence colon polyp development [20,22]. Persons reporting increased levels of stress have also reported increased smoking, poor diet and low levels of physical activity [29,30]. Each of these factors have been associated with colon polyp development.How do you prevent colon polyps from growing? ›
- get regular physical activity.
- don't smoke cigarettes , and if you do smoke, quit.
- avoid drinking alcohol.
- lose weight if you're overweight.
Cruciferous vegetables, including broccoli, brussel sprouts, and cabbage, also contain properties that can fight against cancer. A diet high in fruits, vegetables, and unprocessed grains can be especially beneficial for gut health and the prevention of colon polyps.What kind of pain do colon polyps cause? ›
Pain. Large polyps can obstruct the bowel and cause abdominal pain or cramping. Bleeding. Small tears in your anus or hemorrhoids can lead to blood after a bowel movement.Do all bowel cancers start as polyps? ›
Most colorectal cancers start as a growth on the inner lining of the colon or rectum. These growths are called polyps. Some types of polyps can change into cancer over time (usually many years), but not all polyps become cancer. The chance of a polyp turning into cancer depends on the type of polyp it is.Do colon polyps affect bowel movements? ›
Changes in Bowel Movements – Sometimes colon polyps can lead to constipation or diarrhea that persists for longer than a week, as well as general changes in bowel habits. Changes in Stool Color – Blood can wind up in your stool, often causing your stool to appear black or much darker in color.Can sugar cause colon polyps? ›
High sugar and SSB intake during adolescence was positively associated with increased risk of colorectal adenoma (particularly rectal adenoma), but not serrated lesions. Notably, sugar and SSB intake during adulthood was not associated with risk of colorectal adenoma.
What supplements prevent colon polyps? ›
Folic acid or folate seemed to be protective for especially those who received over 400 micrograms a day from food and/or a multivitamin and began taking it before polyps began to form. It may also be of benefit in colon cancer prevention.What should you not do after a colonoscopy? ›
Colonoscopy Recovery: After the Procedure
The effects of the sedation could last up to a day, so you should not drive or operate any machinery until the following day. You may feel gassy or bloated for a while after the procedure because of the air that was injected into your intestine during the colonoscopy.
If they found precancerous cells, there is no need for any additional treatment as long as they removed the entire polyp. Removing the tissue stops the development of cancer. Since you are still at an increased risk, we will likely recommend repeating the screening every three to five years in the future.How common are colon polyps in 70 year olds? ›
Colon polyps are extremely common among adults 50 years of age and older, occurring in over 40 percent of individuals who undergo screening colonoscopy.What happens if they find cancerous polyps during a colonoscopy? ›
In most cases, only a polypectomy and/or a local excision is needed to treat this stage of cancer. A polypectomy or local excision involves removing the polyp in its entirety during a colonoscopy. Additional treatment may be needed if a polyp or tumor is too big to be removed through local excision.Do colon polyps always grow back? ›
Once a colorectal polyp is completely removed, it rarely comes back. However, at least 30% of patients will develop new polyps after removal. For this reason, your physician will advise follow-up testing to look for new polyps. This is usually done 3 to 5 years after polyp removal.Can I have breakfast the day of colonoscopy? ›
Before 10:00 am, you may have a small, light breakfast. Examples of a light breakfast are: eggs, soup or broth with noodles (no meat or vegetables), white crackers, white rice, white potatoes, white bread, Boost® or Ensure®. At 10:00 am, begin a clear liquid diet. Do not eat anything solid.When should I start prep for a 7am colonoscopy? ›
Typically, bowel prep medication is a solution that you will need to drink starting one day before your procedure. You will be asked to take the colon prep in two doses: the first dose, 3-6 pm the night before your procedure; the second dose, 6-8 hours before your procedure.What is the newest colonoscopy prep? ›
SUTAB includes 24 tablets that must be taken before the colonoscopy. You must split it up into two doses of 12 tablets each.Can you drink colonoscopy prep too early? ›
We ask that you start the bowel prep at the time we gave you. But if you do start one or two hours earlier or later than the time given you, that's fine as long as you follow the clear liquid diet for the day.
How many hours will I poop after colonoscopy prep? ›
What should I do? Bowel movements usually start within two to three hours after taking the prep, but can take longer. If you have not had a bowel movement within three hours of drinking your prep, you may need an extra laxative.How soon can I eat after a colonoscopy? ›
Your doctor may recommend that you eat sparingly, or not at all, in the hours immediately following the procedure. For the rest of that day and the day after, you'll be advised to drink lots of fluid and to eat soft, easily digestible foods which won't irritate your colon.How many times do you go to the bathroom during colonoscopy prep? ›
DAY OF COLONOSCOPY
bowels at least 10-15 times. By the end of your prep, your stool should become a clear, yellow-tinged fluid.
NO whole grains or high-fiber:
- Brown or wild rice.
- Whole grain bread, rolls, pasta, or crackers.
- Whole grain or high-fiber cereal (including granola, raisin bran, oatmeal)
- Bread or cereal with nuts or seeds.
If you have anaemia or symptoms of bowel cancer and have not noticed any signs of bleeding from your bottom, the GP may ask you to do a test where a small sample of your poo is sent to a lab. Your poo will be checked for tiny amounts of blood, which could be a sign of bowel cancer.Can you detect colon cancer without a colonoscopy? ›
Stool based tests, such as Cologuard or FIT, are reasonable alternatives for patients who are unable or unwilling to undergo a standard colonoscopy. Screening saves lives. Talk to your doctor about the appropriate colon cancer screening option for you.What percentage of positive stool samples are cancer? ›
In the study, 3 percent of the people with positive FIT results were diagnosed with colorectal cancer (2,191 total cases).What test can be done instead of a colonoscopy? ›
A colonoscopy is not your only option for screening for colon cancer. Other screening methods are sigmoidoscopy, virtual colonoscopy, a fecal immunochemical test, a fecal occult blood test, or a stool DNA test.Does bloodwork show colon cancer? ›
No blood test can tell you if you have colon cancer. But your doctor may test your blood for clues about your overall health, such as kidney and liver function tests. Your doctor may also test your blood for a chemical sometimes produced by colon cancers (carcinoembryonic antigen, or CEA).What happens if they find cancer during colonoscopy? ›
Usually if a suspected colorectal cancer is found by any screening or diagnostic test, it is biopsied during a colonoscopy. In a biopsy, the doctor removes a small piece of tissue with a special instrument passed through the scope. Less often, part of the colon may need to be surgically removed to make the diagnosis.
Why are colonoscopies not recommended after age 75? ›
“There are risks involved with colonoscopy, such as bleeding and perforation of the colon, and also risks involved with the preparation, especially in older people,” Dr. Umar said.What percentage of colonoscopies find cancer? ›
Here's what we know: As often as 40% of the time, a precancerous polyp — frequently a type called an adenoma — is found during a screening colonoscopy. Colon cancer is found during only in about 40 out of 10,000 screening colonoscopies, Dr. Sand said.How long can you have colon cancer before noticing? ›
Colon cancer, or cancer that begins in the lower part of the digestive tract, usually forms from a collection of benign (noncancerous) cells called an adenomatous polyp. Most of these polyps will not become malignant (cancerous), but some can slowly turn into cancer over the course of about 10-15 years.What percentage of colonoscopies come back positive? ›
If a stool-based test is positive, the follow-up colonoscopy may be considered diagnostic and fall under the patient's deductible. This is important to know because the false positive rate (test coming back positive when everything is completely normal) is about 13%.Is colon cancer treatable? ›
Cancer of the colon is a highly treatable and often curable disease when localized to the bowel. Surgery is the primary form of treatment and results in cure in approximately 50% of the patients. Recurrence following surgery is a major problem and is often the ultimate cause of death.Is bowel cancer curable? ›
If it's detected early enough, treatment can cure bowel cancer and stop it coming back. Unfortunately, a complete cure is not always possible and there's sometimes a risk that the cancer could come back at a later stage. A cure is highly unlikely in more advanced cases that cannot be removed completely by surgery.