Colorectal Cancer

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Screening for Colorectal Cancer (CRC)

Translations of ACG CRC Infographic

ACG Colorectal Cancer Awareness Infographic

New Age to Start CRC Screening: 45 is the New 50

Colorectal Cancer You Can Prevent It

ACG Colorectal Cancer Screening Options

Colorectal Cancer Screening Blood Test

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Overview

• What is colorectal cancer?

  Colon cancer is a disease in which cancer cells grow in the large intestine also called the colon.

  Rectal cancer is a type of colon cancer that grows in the rectum which is the part of your intestine closest to the anus. These two cancers are typically grouped together under the common term of colorectal cancer.

  Colorectal cancers grow from abnormal pre-cancerous tissue called polyps.

• How common is colorectal cancer?

  In the United States, colorectal cancer is the fourth most common cancer.

  The lifetime risk of colorectal cancer for men is 1 in 23 and for women is 1 in 25. About 150,000 Americans are diagnosed with colorectal cancer each year.

  Around 50,000 people will die from colorectal cancer each year, making it the second most common cause of death from cancer.

  While the overall death rate from colorectal cancer has been decreasing, there has been an increase in colorectal cancer diagnoses in people under 50 years old.

Screening

• Who should get screened for colorectal cancer and why?

  Screening lowers your chance of getting sick or dying from colorectal cancer.

  ACG recommends colorectal cancer screening in average-risk individuals between age 45 and 75 years to reduce pre-cancerous growths called advanced adenomas, reduce colorectal cancer, and reduce death from colorectal cancer.

  Some people have higher risks of cancer. For example, if you have family members with colon or rectal cancer or if you have an inflammatory bowel disease you may need to be screened at a younger age.

• How can I get screened for colorectal cancer?

  Best Screening Test - Colonoscopy:

  A colonoscopy is a procedure where a camera looks for growths called polyps in your entire colon (large intestine) and rectum using a colonoscope. During a colonoscopy, your doctor can both detect and remove polyps during colonoscopy and prevent colorectal cancer.

  To prepare for a colonoscopy you will adjust your diet in advance and will drink medications (a bowel prep) to clear stool from your colon. You are usually given medications to make sure you are comfortable and/or asleep during the colonoscopy and will need a ride home. Colonoscopy is the most commonly performed gastrointestinal procedure in the United States.

  Colonoscopy with removal of polyps offers long term protection against developing colorectal cancer or dying from it.

  Best Alternative to Colonoscopy - Stool Tests:

  For people that prefer not to have a colonoscopy, there are two stool tests that can detect changes in the stool that may be from colorectal cancer.

  You collect a small stool sample at home in a kit or cup that has been given to you and then you return the sample to a laboratory either through the mail or in person.

  These tests detect blood or altered DNA in the stool as a first step. A positive result would lead to the second step of colonoscopy for further examination.

  1. FIT: One test is call called FIT which stands for “Fecal Immunochemical Test” and can detect blood in the stool.
     • This test should be done every year.
     • A positive FIT requires a follow-up colonoscopy.
  
  
  2. FIT-DNA: The other test is called a FIT-DNA test. The only current FDA approved test available is Cologuard®.
     • This test can detect blood or several types of abnormal DNA associated with colon cancer or precancerous polyps.
     • This test is more sensitive than FIT alone, but your chance of getting a false positive may increase with advancing age.
     • If FIT-DNA is negative, a repeat screening is needed in three years.
• Are there alternative colorectal cancer screening options besides stool-based tests and colonoscopy?

  Colonoscopy, FIT, and FIT-DNA stool tests are the best forms of colorectal cancer screening as supported by studies and guidelines. However, there are other tests to screen for colorectal cancer as outlined below. The below tests have less evidence and should be considered only when colonoscopy or FIT/FIT-DNA tests are not available. In addition, these tests may be less available and may not be covered by insurance.

  Flexible Sigmoidoscopy

  • A procedure where a camera looks inside part of the colon (the left side) and can diagnose colorectal cancer or remove polyps in this area if seen.
  • It is done with or without medications to make you sleep.
  • It should be repeated every 5 years if performed on its own or every 10 years if it is combined with a FIT test every year.
  • If the test is abnormal, you will need a colonoscopy.

  Computerized Tomography Colonography (CTC)

  • A radiology study where you drink medicine (bowel prep) to clear stool from your colon and then go through a machine that takes pictures of your intestines to look for polyps or cancer. A small tube is inserted into the rectum to inflate the colon with air. You are awake during the study.
  • If the test is abnormal, you will need a colonoscopy.
  • This test should be repeated every 5 years.

  Colon Capsule

  • A study where you swallow a small camera that takes pictures of your intestines from the inside. A physician reviews the images to look for polyps or cancer.
  • If the test is abnormal, you will need a colonoscopy.

  Blood Test: Cell-Free DNA (cfDNA)

  • A lab test that looks for abnormal DNA in the blood that may signify colon or rectal cancer.
  • While this test is good at detecting cancer, it does not detect colon polyps and is not able to prevent colon or rectal cancer.
  • As of February 2026, the only cell-free DNA test available is Shield.
  • If the test is abnormal, you will need a colonoscopy.
  • This test should be repeated every 3 years.

Symptoms

• What are the symptoms of colorectal cancer?
  • Most early colon and rectal cancers do not cause symptoms. This is why screening for colorectal cancer is so important!
  • Sometimes people will see blood in the toilet or in their stool due to colorectal cancer.
  • People can develop belly (abdominal) pain or experience constipation (difficulty having a bowel movement) from colorectal cancer.
  • Sometimes people will have low blood counts (anemia) and low iron levels from colorectal cancer, which can make them feel tired.
  • Weight loss can also be caused by cancer.
  • You should see your doctor right away if you have any of these symptoms.
• Why should you get checked for colorectal cancer even if you have no symptoms?
  • Abnormal tissue (polyps) can grow for years before turning into cancer.
  • Finding these polyps before they turn into cancer can help prevent cancer.
  • Detecting cancer at an early stage is easier to treat and can improve survival compared to finding cancer later after it has spread to other parts of the body.

Risk Factors

• What are the risk factors for colorectal cancer?
  • Age: The older you are, the higher the risk of colon and rectal cancer. All people with no risk factors other than age should get screened starting at age 45.
  • Family history of colon or rectal cancer: If you have a first-degree relative (mother, father, sister, brother, child) or multiple other relatives with colon or rectal cancers, or polyps called “advanced adenomas,” you are at increased risk of colon or rectal cancer.
    • You may be recommended to get a colonoscopy at a younger age and have them done more frequently.
    • You should discuss your screening plan with a gastroenterologist.
  • Inflammatory Bowel Disease (IBD): IBD in the colon, such as Ulcerative Colitis or Crohn’s Disease, can increase your risk of colon or rectal cancer.
    • If you have IBD, you should discuss your colon and rectal cancer screening with your gastroenterologist.

Treatment Options

Please see the National Cancer Institute resource page for information on the stages of colon cancer, an overview of treatment options, and treatment options for each stage.

Author(s) and Publication Date(s)

Ryan Hoff, DO, PeaceHealth Gastroenterology, Vancouver, WA and Joshua L. Hudson, MD, MSc, University of North Carolina, Chapel Hill, NC - Updated February 2026

Colonoscopy FAQs

• What is Colonoscopy?

  Colonoscopy is a procedure which enables a physician (usually a gastroenterologist) to directly image and examine the entire colon. It is effective in the diagnosis and/or evaluation of various GI disorders (e.g. colon polyps, colon cancer, diverticulosis, inflammatory bowel disease, bleeding, change in bowel habits, abdominal pain, obstruction and abnormal x-rays or CT scans) as well as in providing therapy (for example, removal of polyps or control of bleeding). It is also used for screening for colon cancer. A key advantage of this technique is that it allows both imaging of abnormal findings and also therapy or removal of these lesions during the same examination. This procedure is particularly helpful for identification and removal of precancerous polyps.

• What is a Colonoscope?

  A colonoscope is a flexible and steerable instrument to evaluate the entire colon (large intestine). The large intestine is approximately 3 – 4 feet long. A colonoscope is engineered such that biopsies of suspicious areas can be obtained, and polyps (which may turn into cancer) can be removed.

• Has colonoscopy been shown to be effective in preventing cancer of the colon and saving lives?

  Yes. Colonoscopy accomplishes this by detecting and removing polyps, and detecting early cancers. Recent data show that both the number of new cases of colon cancer (incidence) and deaths from the disease are decreased when colonoscopy is performed according to established guidelines.

• If colonoscopy is so effective at detecting polyps, colon cancer and saving lives, why aren't more people having it?

  The most common reason patients cite for not getting a colonoscopy is that their doctor did not discuss it with them. The next most common reason is fear or avoidance of the preparation (“prep”), which involves taking a laxative which causes temporary diarrhea for several hours. In addition, many people are simply unaware that they need colon cancer screening.

• What is the "prep" for colonoscopy like? How many different preps are out there?

  This is an important obstacle in the eyes of many patients to getting a colonoscopy, but it need not be!

  There are a variety of preparation methods for colonoscopy ranging from liquids (of varying quantity) with or without enemas, to pills, which rid your colon of feces. A clean colon is essential to allow for a careful examination for polyps or other abnormalities. Your doctor can discuss and prescribe the most appropriate preparation method for you, taking into account various factors such as your age, personal preferences, kidney function and physical stamina.

  • The most popular preparation used for colonoscopy involves drinking a volume of solution of polyethylene glycol (PEG). This solution causes a diarrhea that effectively rids the colon of its contents. Various fruit flavors are available and patients have several hours to drink it. Usually a patient will have clear liquids the day of the preparation (day before the colonoscopy) and then take half of the prep in the late afternoon or that evening. The other half is done approximately 5 hours before coming in for the test the following day. Patients are encouraged to drink a lot of fluids and to continue clear liquids up until 2 hours before their scheduled procedure. Before going to bed, many doctors also prescribe a laxative pill (e.g. Dulcolax®) that helps with the evacuation process.
  • Smaller volumes of solution (e.g. MoviPrep®, HalfLytely®) or pill preparations (e.g. OsmoPrep®) have also recently become available with similarly good outcomes to PEG for people who dread the thought of large volumes of liquid.
  • Another preparation involves a phosphate solution (called Fleet® Phospho-soda) which consists of two (2) rounds of phosphate rich liquid of 45ml each the night before and day of the exam. It is essential to drink at least 2 quarts of water with these preps to replace losses.
  • Alternatively, a phosphate tablet preparation of about 30 pills is available and is also very effective for colon cleansing and is preferred by some patients. This preparation also requires that you drink at least 2 quarts of water to replace losses.

  Phospho-soda® prep should be avoided in patients with significant heart or kidney problems, in elderly patients who have difficulty maintaining hydration and with caution in patients with significant liver problems

  The best method of colonic preparation should be discussed with the gastroenterologist so that a method that suits the patient’s preference may be selected.

• Is colonoscopy painful? Will I be sedated?

  No, colonoscopy is usually not painful! Almost all colonoscopies can be performed using “intravenous sedation” or “twilight sedation” in which you are very drowsy, but comfortable and still breathing on your own. The most common type of sedation also has a mild amnesiac effect, so most patients do not even remember the procedure! Your doctor can discuss with you the best form of sedation to suit your needs.

• Will my insurance pay for this procedure?

  Medicare (and most third party payers) will pay for colonoscopy for colon cancer screening, thanks to the hard work of advocacy groups and the efforts of national organizations such as the American College of Gastroenterology (ACG). Regrettably, a recent study showed a low compliance rate for screening (less than 30%) among Medicare patients.

• Are there any complications from colonoscopy?

  Yes, but potential complications are associated with virtually every form of testing done in medicine. Clearly, colonoscopy has been found to be extremely safe when performed by a well trained physician such as a gastroenterologist. Although quite rare, most complications are related to sedation administration (cardiac and respiratory problems); the colon may also become partially torn (perforated) and this may require surgery. Rarely, bleeding from polyp removal or from the procedure itself may require additional treatment such as hospitalization and/or blood transfusions. As one reads about these procedures, the reader should weigh these low risks against the far more frequent complication of developing colon cancer if appropriate testing is NOT done.

• When should I have a colonoscopy?

  If you have no colorectal symptoms, family history of colon cancer, polyps or inflammatory bowel disease you should have your first exam at age 45 whether you are a man or a woman since colon cancer affects both EQUALLY! Recent evidence suggests that African Americans should begin screening earlier at the age of 45.

  If one or more first degree relative (parent, sibling or child) has had a precancerous polyp or colon cancer, the general guideline is to begin colon cancer screening 10 years younger than the youngest age of the family member with colon cancer, or age 40, whichever is younger. There are additional guidelines for suspected or confirmed rare syndromes, and you should discuss these options with your doctor.

Questions and Answers about Quality in Colonoscopy

• Why is quality important in colonoscopy?

  Although colonoscopy has been available in clinical practice for more than 40 years, only in the past 15 years has awareness developed that the success of colonoscopy in preventing colorectal cancer and minimizing complications is very dependent on the skill and competence of the colonoscopist. Colonoscopists differ substantially in the number of precancerous polyps they detect during colonoscopy and in how often they perform colonoscopy in response to both normal and abnormal findings. Awareness of these differences led the U.S. Multisociety Task Force on Colorectal Cancer in 2002, as well as a joint task force of experts from the American College of Gastroenterology and American Society of Gastrointestinal Endoscopy in 2006, to propose quality indicators that colonoscopists can use to measure how effectively and safely they perform colonoscopy. Obviously, patients have an interest in undergoing the most effective and safe colonoscopy possible, and achieving these goals requires a colonoscopist who is committed to high quality.

• Does the quality of examination differ among colonoscopists from different specialties?

  Studies have shown average performance of colonoscopy by gastroenterologists to be superior to that of primary care physicians in three different areas of colonoscopy performance. First, three population-based studies have found that gastroenterologists performing colonoscopy are less likely to miss colorectal cancer than are primary care physicians who perform colonoscopy. This may reflect the more extensive training that gastroenterologists receive in this procedure and their higher volumes of colonoscopy in practice. Second, gastroenterologists’ patients are less likely to incur serious complications during colonoscopy, such as perforation or making a hole in the colon, compared to primary care physicians. Third, gastroenterologists are less likely than both primary care physicians and general surgeons to perform colonoscopy at intervals that are considered too short according to current guidelines. Whether this difference reflects a lack of confidence among primary care physicians and general surgeons in the quality of their colonoscopy or lack of awareness of current guidelines is unknown.

• Is there variation in quality of performance among members of the same specialty?

  Even though gastroenterologists have on average the highest level of training and their examinations have been shown on average to be superior to primary care physicians, there is considerable variation among gastroenterologists in their detection rates of precancerous polyps. Therefore, it is essential that every colonoscopist, regardless of specialty, makes measurements to establish that their examinations are effective. It is very reasonable and appropriate for patients to ask questions of their colonoscopist about whether quality measurements are being made and their results.

• How can I be sure that I will receive a careful examination of my colon?

  The measurement that best reflects how carefully colonoscopy is performed is a doctor’s "adenoma detection rate." This rate is defined as the percentage of patients age 50 and older undergoing screening colonoscopy, who have one or more precancerous polyps detected. This rate should be at least 25% in men and 15% in women. A secondary measure of careful examination is that doctors should have an average withdrawal time of at least six minutes. The withdrawal time is the time it takes to remove the scope from the colon. This interval is important because this is the phase of colonoscopy when most doctors actually examine the colon systematically for polyps. It is perfectly reasonable to expect doctors to have measured their adenoma detection rate and to record their withdrawal time. It is also reasonable to ask for a copy of the colonoscopy report that documents that the colonoscope was advanced to the very beginning of the colon and that the landmarks of that portion of the colon (called the "cecum") have been documented by notation in the report and by photography.

• Why is bowel preparation for colonoscopy important, and what can I do to make sure my colon is thoroughly cleansed for the procedure?

  Colonoscopy is a video examination of the colon. The video camera and the colonoscope, like any other video camera, cannot see through solids. Therefore, the colon must be thoroughly cleansed to provide the doctor the best opportunity possible for a thorough and detailed examination.Be sure to pick up and read your written bowel preparation instructions at least several days before your colonoscopy. Go over the instructions and make sure you have all of the materials needed to complete the preparation.The most effective bowel preparations involve "split" dosing of the laxatives, in which half of the preparation is taken on the morning of the examination, usually 4 to 5 hours before the time of the scheduled colonoscopy, and completed at least 2 to 3 hours before that time. If you are scheduled at 7 or 8 in the morning, this will mean getting up very early to take the second half of the preparation. If the instructions call for split dosing, do not alter the timing of the doses. It is worth the inconvenience of getting up in the middle of the night to make sure that you have a very effective preparation. The timing of the second dose in relationship to the colonoscopy is critical. If too long an interval is allowed between the end of the second half of the preparation and the timing of the colonoscopy, mucus and secretions will come out of the small intestine and stick to the cecum and right colon.

• Summary

  To ensure an effective and safe colonoscopic examination, find a well-trained colonoscopist who is committed to making quality measurements. It is fair to ask the colonoscopist to be sure to do a slow and careful examination and to provide a copy of the report that documents and photographs the complete extent of examination. Take the bowel preparation instructions seriously. Pick up the written instructions early, read them early, and follow them carefully. When colonoscopy is done carefully and with an effective preparation, it is a very powerful cancer prevention technique.

Your Doctor has Ordered a Colonoscopy: What Questions Should You Ask?

• Is the doctor performing your colonoscopy a Gastroenterologist?

  A Gastroenterologist is a specialist in gastrointestinal diseases and has received special training in colonoscopy. Gastroenterologists perform more colonoscopies by far than any other specialty. Non-gastroenterologists are five times more likely to miss colorectal cancer during colonoscopy than Gastroenterologists.¹

  ¹ Rex DK, Rahmani E, Haseman JH, et al. Relative sensitivity of colonoscopy and barium enema.

• What training in colonoscopy did the doctor receive?

  Proper training in colonoscopy is necessary not only to increase the chance that the procedure can be completed and any necessary treatments applied, but also to be sure that abnormal results can be properly interpreted. The American Society for Gastrointestinal Endoscopy recommends that persons performing colonoscopy complete a fellowship program in gastroenterology or receive training in colonoscopy during a surgical residency.

• How many colonoscopies has the doctor performed? How many perforations has the doctor had?

  Many Gastroenterologists have performed many thousands of colonoscopies. A colonoscopist should know the rate at which their procedures have been associated with a perforation or making a hole in the colon. This rate should certainly be below 1 in 500 examinations and many experts have rates of perforation well below 1 in 1000.

• How often does your doctor complete the colonoscopy?

  Experienced colonoscopists reach the very beginning of the large intestine (the cecum) in more than 90% of cases and in more than 95% of patients who are undergoing screening. Screening is the process of checking people who have no symptoms for colon polyps and cancer.

• Can the doctor remove polyps from your colon?

  Persons performing colonoscopy must be trained in the removal of polyps. Although even Gastroenterologists may refer a patient with a large polyp to a special expert in the removal of polyps, a trained colonoscopist can remove the overwhelming majority of routine polyps.

What is a gastroenterologist?

• What is a Gastroenterologist?

  A Gastroenterologist is a physician with dedicated training management of diseases of the gastrointestinal tract and liver.

• What is Gastroenterology?

  Gastroenterology is the study of the normal function and diseases of the esophagus, stomach, small intestine, colon and rectum, pancreas, gallbladder, bile ducts and liver. It involves a detailed understanding of the normal action (physiology) of the gastrointestinal organs including the movement of material through the stomach and intestine (motility), the digestion and absorption of nutrients into the body, removal of waste from the system, and the function of the liver as a digestive organ. It includes common and important conditions such as colon polyps and cancer, hepatitis, gastroesophageal reflux (heartburn), peptic ulcer disease, colitis, gallbladder and biliary tract disease, nutritional problems, Irritable Bowel Syndrome (IBS), and pancreatitis. In essence, all normal activity and disease of the digestive organs is part of the study of Gastroenterology.

• Training

  A Gastroenterologist must first complete a three-year Internal Medicine residency and is then eligible for additional specialized training (fellowship) in Gastroenterology. This fellowship is generally 2-3 years long so by the time Gastroenterologists have completed their training, they have had 5-6 years of additional specialized education following medical school.

  Gastroenterology fellowship training is an intense, rigorous program where future Gastroenterologists learn directly from nationally recognized experts in the field and develop a detailed understanding of gastrointestinal diseases. They learn how to evaluate patients with gastrointestinal complaints, treat a broad range of conditions, and provide recommendations to maintain health and prevent disease. They learn to care for patients in the office as well as in the hospital.

  Gastroenterologists also receive dedicated training in endoscopy (upper endoscopy, sigmoidoscopy, and colonoscopy) by expert instructors. Endoscopy is the use of narrow, flexible lighted tubes with built-in video cameras, to visualize the inside of the intestinal tract. This specialized training includes detailed and intensive study of how and when to perform endoscopy, optimal methods to complete these tests safely and effectively, and the use of sedating medications to ensure the comfort and safety of patients. Gastroenterology trainees also learn how to perform advanced endoscopic procedures such as polypectomy (removal of colon polyps), esophageal and intestinal dilation (stretching of narrowed areas), and hemostasis (injection or cautery to stop bleeding). Importantly, Gastroenterologists learn how to properly interpret the findings and biopsy results of these studies in order to make appropriate recommendations to treat conditions and/or prevent cancer. Some Gastroenterologists also receive directed training in advanced procedures using endoscopes such as endoscopic biliary examination (endoscopic retrograde cholangiopancreatography or ERCP), removal of tumors without surgery (endoscopic mucosal resection or EMR), placement of internal drainage tubes (stents) and endoscopic ultrasound (EUS). This provides them with the training necessary to non-surgically remove stones in the bile ducts, evaluate and treat tumors of the gastrointestinal tract and liver, and provide minimally invasive alternatives to surgery for some patients.

  The most critical emphasis during the training period is attention to detail and incorporation of their comprehensive knowledge of the entire gastrointestinal tract to provide the highest quality endoscopy and consultative services. The final product is a highly trained specialist with a unique combination of broad scientific knowledge, general Internal Medicine training, superior endoscopic skills and experience, and the ability to integrate these elements to provide optimal health care for patients.

  This advanced fellowship training is overseen by national societies committed to ensuring high quality and uniform education. These groups include the American Board of Internal Medicine, the American College of Gastroenterology, the American Gastroenterological Association, and the American Society for Gastrointestinal Endoscopy. These groups carefully scrutinize the educational experience of each program to ensure that every Gastroenterology trainee receives the highest quality training. Once fellows successfully complete their training they are considered “Board Eligible.” They are then qualified to take the Gastroenterology board certification test administered by the American Board of Internal Medicine. Once they have successfully completed this examination they are “Board Certified.”

• FACG, FACP — What do all the letters after your doctor's name mean?

  Some Gastroenterologists receive special recognition from national societies when they demonstrate extraordinary achievement in research, teaching, or other unique service to the field of Gastroenterology. The American College of Gastroenterology and the American College of Physicians designate such physicians as “Fellows” and the suffixes FACG and FACP are added to denote these honors. This means that these physicians have fulfilled the respective organizations’ rigorous requirements to gain this added distinction.

• What makes Gastroenterologists different?

  The unique training that Gastroenterologists complete provides them with the ability to provide high quality, comprehensive care for patients with a wide variety of gastrointestinal ailments. Gastroenterologists perform the bulk of research involving gastrointestinal endoscopic procedures as well as the interpretation of results, and are considered experts in the field. Studies have shown that Gastroenterologists perform higher quality colonoscopy examinations and comprehensive consultative services when compared to other physicians. This translates into more accurate detection of polyps and cancer by colonoscopy when performed by Gastroenterologists, fewer complications from procedures and fewer days in the hospital for many gastrointestinal conditions managed by trained gastroenterology specialists. It is this ability to provide more complete, accurate, and thorough care for patients with gastrointestinal conditions, which distinguishes Gastroenterologists from other physicians that provide some similar services.

Audio Podcasts & Videos

ACG Experts Answer Your Most Common Questions on CRC and Colonoscopy: