Benefits and Risks of Colonoscopy

Medically Reviewed By William C. Lloyd III, MD, FACS
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Senior African American woman in hospital gown smiling at unseen female doctor
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Early detection of colon cancer is well known as the greatest benefit of getting a colonoscopy. Colon cancer screenings can catch precancerous polyps or abnormal tissue early and decrease your chance of dying from colorectal cancer. Another plus is that colonoscopies are routine procedures, and the risk of a complication is very low. Fewer than 10 out of 10,000 patients will experience severe problems after a colonoscopy. Even so, as with any medical procedure, there are some potential risks with colonoscopies. Even though serious complications are rare, it’s still important to understand colonoscopy risks. 

Colon Cancer Screening

A traditional colonoscopy is a procedure usually performed by a gastroenterologist using a long, flexible tube with a video camera at the end. This tube is called a colonoscope, and it is inserted into the colon, or large intestine, through the anus. A nurse anesthetist administers a sedative so that you reach conscious sedation (you may fall asleep during the procedure), although some colonoscopy procedures may involve deeper sedation. Either way, you won’t feel the colonoscope. 

Using the camera, the doctor will be able to see potential signs of colon cancer, such as any polyps or abnormalities in the colon or rectum. The doctor can remove polyps or take a biopsy of abnormal tissue through the colonoscope and send it to a lab for analysis. 

Types of Colonoscopy

Besides a traditional colonoscopy, there are other procedures that your doctor can use to detect colon cancer. These include: 

  • Virtual colonoscopy: Also called a CT colonography, a virtual colonoscopy uses a CT scanner to create a 3D image of your colon. Your doctor looks for polyps or abnormal tissue on the 3D image. It requires a shorter tube placed into the rectum that inflates your colon with air to reveal a clearer picture of the large intestine. The procedure is quicker than a traditional colonoscopy and comes with fewer complications. They are usually performed every five years.

  • Flexible sigmoidoscopy: For this procedure, a short scope is inserted into the lower portion of your colon, the most common place for colorectal cancer to develop. While this screening examines the bottom portion of the colon rather than the entire length, it still has a high rate of accuracy in detecting cancer. Doctors recommend this procedure every five years.

  • Stool tests: The two types of stool tests are much less accurate than a colonoscopy, but they are not invasive. You will collect the stool at home and send it to a lab. Cancer guidelines recommend stool tests every year.

Benefits of Colonoscopy

When it comes to colorectal cancer, the earlier a doctor can detect abnormalities in the colon wall, the better. Because colon cancer may not have any symptoms in its early stages, colonoscopies save lives by detecting signs of cancer sooner. A traditional colonoscopy offers the highest accuracy of the various colon cancer screening options available.

The greatest benefit of a traditional colonoscopy is that the doctor can immediately remove polyps—which can develop into cancer over time—or take a biopsy of abnormal tissue. Other colon cancer screenings may require a follow-up colonoscopy if your doctor discovers abnormalities. Removing polyps and analyzing abnormal tissue helps prevent colorectal cancer. 

Risks of Colonoscopy 

A colonoscopy is a safe procedure for most healthy people, but it does come with some risk of complications. Colonoscopy risks include:

  • Bleeding: It’s normal to see a little blood in your stool if your doctor removes a polyp or takes a biopsy. However, major bleeding can occur and needs treatment. While it’s rare, it can be life threatening.

  • Perforation: Rarely, a colonoscopy can tear the colon wall, and you could need surgery to repair it.

  • Reaction to anesthesia or sedative: There’s a chance of an adverse reaction to the drugs used during the colonoscopy.

Studies have concluded that colonoscopy risks in the elderly often outweigh the benefits. However, patients older than age 70 are more likely to have complications, so older adults may choose other, less invasive methods of colon cancer screening.

When You Need a Colonoscopy 

Healthy people who are at average risk of developing colorectal cancer typically need a colonoscopy every 10 years, starting at age 50, or age 45 for African Americans, who have a higher risk of colon cancer. If you have signs of colon cancer or if you have a higher risk of developing colorectal cancer, you may need a colonoscopy more frequently to screen for the disease.

Symptoms and signs of colon cancer include: 

Risk factors for colon cancer include:

  • Age 50 or older

  • African American ancestry

  • Biologically male

  • Personal or family history of polyps or colon cancer

  • Chronic inflammation in the colon

  • Obesity or poor diet

  • Lack of exercise

  • Diabetes

  • Smoking or heavy alcohol use

After a Colonoscopy

After having a colonoscopy, your doctor may have some special instructions for you to follow as you recover. Following the instructions will help you avoid complications. Be sure someone will be able to take you home after the procedure because it may take an hour or more for the sedative to wear off, and you still may be groggy. You could feel gassy afterward, but walking can help relieve discomfort. 

You may need to eat a specific diet for a while if abnormal tissue was removed. If the colonoscopy result is negative, meaning no polyps or abnormal tissue, you can return to your regular diet the day after your colonoscopy. You may have some blood in your stool—and that’s normal. If it doesn’t stop soon after the colonoscopy or becomes heavy, or if you have severe pain or fever, call your doctor. Your doctor can evaluate you and treat the underlying problem, such as bleeding or infection, so the problem doesn’t get worse.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Feb 21
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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