A colonoscopy is a procedure used to examine the lining of the large intestine (colon) and rectum. It is performed using a colonoscope, a long, thin, flexible tube equipped with a light and a small video camera at its tip.
The camera transmits high-quality images to a monitor, allowing the physician to carefully inspect the colon for abnormalities such as polyps, inflammation, bleeding, ulcers, and tumors. During the procedure, the physician may also obtain biopsies or perform treatments when necessary.
Colonoscopy is considered the most accurate method for evaluating the colon and is an important tool for the prevention, diagnosis, and treatment of colorectal diseases.
Reasons for a colonoscopy
Your physician may recommend a colonoscopy for the following reasons:
- Colorectal cancer screening
- Personal history of colon polyps
- Family history of colorectal cancer or polyps
- Rectal bleeding
- Blood in the stool
- A positive stool-based screening test
- Unexplained changes in bowel habits
- Chronic diarrhea
- Chronic constipation
- Abdominal pain
- Unexplained weight loss
- Iron-deficiency anemia
- Evaluation and monitoring of inflammatory bowel disease (Crohn's disease or ulcerative colitis)
- Follow-up of previously identified colon polyps or colon cancer
Reasons for a repeat colonoscopy
A repeat colonoscopy may be recommended to:
- Monitor patients with a history of colon polyps
- Perform surveillance after colorectal cancer treatment
- Monitor inflammatory bowel disease
- Evaluate ongoing gastrointestinal symptoms
- Follow up on previously abnormal findings
- Complete an examination if bowel preparation was inadequate during a previous procedure
The timing of a repeat colonoscopy depends on your individual risk factors and the findings from previous examinations.
Benefits of colonoscopy
A colonoscopy is both diagnostic and therapeutic: the procedure can identify abnormalities and, in many cases, treat them during the same examination.
- Early detection of colorectal cancer
- Prevention of colorectal cancer through removal of precancerous polyps
- Identification of the cause of gastrointestinal symptoms
- Collection of tissue samples (biopsies) for laboratory analysis
- Treatment of certain sources of gastrointestinal bleeding
Therapeutic procedures that may be performed
- Removal of colon polyps (polypectomy)
- Biopsy of abnormal tissue
- Treatment of bleeding lesions
- Dilation of narrowed areas (strictures)
- Removal of certain foreign bodies
How to prepare
Proper bowel preparation is essential for a successful colonoscopy. A clean colon allows the physician to clearly visualize the intestinal lining. Please inform your healthcare team if you have heart disease, lung disease, diabetes, kidney disease, bleeding disorders, or any other significant medical condition.
- Follow the bowel preparation instructions provided by your physician.
- Consume only clear liquids as directed before the procedure.
- Do not eat solid foods during the period specified by your physician.
- Take the prescribed bowel-cleansing solution exactly as instructed.
- Inform your physician if you take blood thinners, antiplatelet medications, insulin, or diabetic medications.
- Do not drink anything within the time frame instructed by your physician before the procedure.
What to expect during the procedure
- An intravenous (IV) line will be started.
- Medications will be administered to help you relax and remain comfortable.
- You will wear a hospital gown.
- You will lie on your left side during the procedure.
- The physician will gently insert the colonoscope through the rectum and advance it through the colon.
- Air or carbon dioxide may be introduced to improve visualization.
- The physician will carefully examine the lining of the colon and may remove polyps or obtain biopsies if necessary.
- The procedure generally takes approximately 20–45 minutes, depending on the findings and treatments performed.
After the procedure
- You will remain in the recovery area for observation until the effects of sedation begin to wear off.
- Mild bloating, gas, or abdominal cramping may occur and usually resolves quickly.
- Your physician will discuss preliminary findings with you and your family.
- If biopsies are taken or polyps removed, pathology results are usually available within 3–7 days.
- A report will be sent to your referring physician.
Important instructions after discharge
- Arrange for a responsible adult to drive you home.
- Do not drive, operate machinery, or make important decisions for at least 24 hours.
- Resume your diet as directed by your physician.
- Drink plenty of fluids unless otherwise instructed.
Contact your physician immediately if you experience
- Severe abdominal pain
- Persistent or heavy rectal bleeding
- Fever or chills
- Dizziness or fainting
- Persistent nausea or vomiting
Risks and possible complications
Colonoscopy is generally a safe procedure, and most patients experience no significant complications. Possible complications include:
- Bleeding, especially after polyp removal or biopsy
- Perforation (a tear in the wall of the colon)
- Adverse reactions to sedation medications
- Infection (rare)
- Incomplete examination requiring additional testing
Although complications are uncommon, they may rarely require hospitalization, additional procedures, or surgery. Your physician will discuss any specific risks related to your procedure.
Colorectal cancer screening
Colonoscopy is the gold standard for colorectal cancer screening. Screening can detect cancer at an early stage, when treatment is most effective, and can prevent cancer through the removal of precancerous polyps.
Individuals at average risk should discuss screening recommendations with their healthcare provider. Patients with a family history of colorectal cancer or other risk factors may require earlier or more frequent screening.