Colonoscopy is an exam used to look for changes in the large intestine and rectum.

During a colonoscopy, a long, flexible instrument is inserted into the rectum. A camera on the end of the instrument allows the doctor to see the inside of the colon.

A colonoscopy is used to check for swollen tissue, polyps or cancer. Polyps and other types of abnormalities can be removed during a colonoscopy.

Colorectal cancer, a leading cause of cancer-related deaths, can often be prevented by removing benign polyps identified during a colonoscopy.

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Why do I need a colonoscopy?

A colonoscopy can prevent, diagnose and treat some problems in the colon and rectum.

Your doctor might recommend you have a colonoscopy for routine cancer screening at a certain age, or if you experience:

  • Persistent abdominal pain: ongoing discomfort in the abdomen that does not subside
  • Chronic diarrhea or constipation: long-lasting changes in bowel habits that remain unresolved
  • Unexplained weight loss: losing weight significantly without trying or any obvious reason
  • Blood in your stool: observing red or dark blood in your bowel movements
  • A change in bowel habits: new or unusual bowel patterns, such as frequency or stool consistency

Colonoscopy screening

Colonoscopy is used as a routine screening tool for colorectal cancer. The American Cancer Society recommends that most people get regular screenings by age 45. Some people might be recommended to get earlier or more frequent screening due to certain risk factors.

You might be due for a colonoscopy if:

  • Adults aged 45 and older: Regular screening for colorectal cancer should begin at age 45, as recommended by the American Cancer Society, due to increasing rates of colorectal cancer in younger populations.
  • Individuals with a family history of colorectal cancer or polyps: If you have a first-degree relative who has been diagnosed with colorectal cancer or polyps, you are at an increased risk and may need to start screening at an earlier age.
  • People with a personal history of colorectal cancer or adenomatous polyps: If you’ve had colorectal cancer or benign growths (polyps) removed in the past, regular follow-up colonoscopies are necessary to monitor for recurrence.
  • Individuals with chronic inflammatory bowel diseases: Conditions like Crohn’s disease or ulcerative colitis increase your risk of colorectal cancer, necessitating more frequent surveillance.
  • Patients with a personal or family history of hereditary colorectal cancer syndromes: Conditions like Lynch syndrome or familial adenomatous polyposis necessitate earlier and more frequent screening.

Consult your health care provider to determine the appropriate timing for a colonoscopy, which is used to detect and remove polyps, diagnose gastrointestinal symptoms, and monitor conditions like inflammatory bowel disease.

Why choose WashU Medicine for colorectal care?

  • Our experts are among the first in North America to offer a treatment that can shrink colorectal tumors before surgery.
  • We have a special program dedicated to caring for people who develop colorectal cancer earlier in life.
  • Gastrointestinal care at WashU Medicine and Barnes-Jewish Hospital is consistently ranked among the best in the nation, according to U.S. News & World Report.

Preparing for the procedure

Preparation for a colonoscopy is crucial because it ensures the colon is thoroughly cleansed, allowing for a clear and unobstructed view of the colon’s lining.

This helps in the accurate detection and assessment of abnormalities such as polyps, lesions, and other potential issues.

Proper preparation minimizes the risk of complications, enhances the effectiveness of the procedure, and reduces the likelihood of needing a repeat colonoscopy due to incomplete or unclear results.

Effective preparation involves:

  • Following a clear liquid diet
  • Taking prescribed laxatives to empty the colon
  • Following specific instructions from your doctor to ensure a thorough exam

Colorectal specialists at WashU Medicine


What to expect on exam day

You can have sedation to remain comfortable during a colonoscopy.

There may be different options for anesthesia. You and a provider will discuss your options and make a plan in advance, so you will know what to expect on the day of the procedure.

The procedure generally lasts 30-60 minutes.

Your vital signs will be monitored throughout to ensure your safety.

After the examination

You’ll spend some time in recovery while the sedation wears off.

You might still feel drowsy for 24 hours after the colonoscopy, so you should have someone drive you home.

Interpreting results

Negative results: No abnormalities found.

Positive results: Polyps or abnormal tissues were detected, which may require removal and biopsies. Further testing or a repeat colonoscopy may be needed sooner. You might need further testing, such as CT scans, MRI or blood tests to assess the extent of the disease.

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Understanding risks involved

A colonoscopy is considered a generally safe procedure with a low risk of complications. However, as with any medical procedure, there are some potential risks, including:

  • Bleeding from a biopsy or polyp removal site: This is usually minor and can often be managed immediately during the procedure.
  • Perforation of the colon or rectum: In rare cases, the colonoscope can cause a tear in the rectum wall, which might require surgical repair.
  • Adverse reaction to sedation: Some people may experience reactions to the sedatives or anesthesia used to keep them comfortable during the procedure, such as breathing difficulties or changes in heart rate.
  • Infections: Though uncommon, there is a slight risk of infection where the tissue is removed or biopsied.
  • Post-procedure discomfort: Mild abdominal cramping, bloating, or gas can occur after the procedure due to the air used to inflate the colon for viewing.

Follow-up exams

Based on findings and personal medical history, your doctor will recommend any follow-up tests.

Early detection of abnormalities can increase the effectiveness of treatment and improve outcomes.

Always consult with your health care provider to determine the best screening interval based on your specific medical history and risk factors.

A colonoscopy is a vital tool for maintaining colorectal health. By understanding the procedure, preparing adequately, and following medical advice, you can ensure that you reap the full benefits of this important screening. If you have any concerns or questions, your health care provider is the best resource to provide information tailored to your specific situation.