Colonoscopy: Your Questions Answered

Colorectal cancer is one of the most common types of cancer diagnosed in the United States, with more than 150,000 new cases expected to be diagnosed in 2024 alone.  It is also the second-most common cause of all cancer deaths in the country.

While these statistics may be shocking, there is good news: Colorectal cancer not only can be caught early, but also prevented through regular screenings.

“Colonoscopy is the gold standard for colorectal cancer screening, and it has the potential to save your life,” says gastroenterologist Anthony Auteri, MD, with Eastern Pennsylvania Gastroenterology and Liver Specialists and Chief, Division of Gastroenterology, Lehigh Valley Health Network (LVHN). “However, some people are hesitant to undergo colonoscopy because of what they’ve heard about the preparation and the procedure. Many of these tales are from years ago before the procedure was modernized. Some recent updates involve lower-volume bowel cleansing preps, more effective sedation, more advanced scopes and the development of more patient-friendly ambulatory endoscopy centers, which many patients prefer over coming to the hospital.”

To ease any concerns you may have about this important screening tool, we’ve answered some common questions below:

Colonoscopy looks for concerning changes in the large intestine (colon) and rectum, allowing them to be identified and removed before they become cancerous.

A typical colonoscopy will take between 20 and 30 minutes. Before the procedure, you will change into a patient gown and lie on a bed. You will be given a sedative so you won’t be awake or feel anything while the procedure is taking place.

During the procedure, a flexible tube with a camera is inserted into the rectum. A gastroenterologist will advance the tube through the length of the colon to make sure there are no abnormal growths or concerning areas.

“It takes about 30 minutes to completely wake up after the procedure, but you likely won’t be in any pain at all,” Dr. Auteri says. “In fact, some people go out for a bite to eat after.”

Colonoscopy isn’t just for viewing the colon and rectum.

If a growth is found during a colonoscopy, your doctor can either remove it entirely during that same appointment or if it is larger and potentially cancerous, can take a small sample biopsy for testing.

Polyps, which are growths that can become cancerous if not removed, are commonly found during colonoscopy.  Almost all colorectal cancers start as benign polyps that can be removed before the cancer occurs. Colonoscopy can find precancerous tumors in early stages before they cause symptoms, allowing individuals to receive treatment sooner.

“On average, we find precancerous polyps in 1 in 4 people over age 45,” Dr. Auteri says. “This tells us that if every eligible individual underwent regular colonoscopy, we could drastically reduce colorectal cancer diagnoses and deaths.”

It is recommended that most people start getting screening colonoscopy at age 45, when precancerous polyps become more prevalent. If you are at higher risk for developing colorectal cancer (based on your family or personal health history), your gastroenterologist may recommend starting screening earlier.

If nothing is found during your colonoscopy, you will often not need another for 10 years. However, if polyps are found or if you are at a higher risk for colorectal cancer, it may be recommended that you get another in three to five years.

Your colon needs to be cleaned out for your procedure so that the gastroenterologist can thoroughly visualize and examine the inner lining of your colon.

To do this, you will need to follow a specific bowel cleansing plan starting 24 hours before your colonoscopy. In addition to following a clear liquid diet, you also will need to drink fluid with laxatives mixed in.  

While most people tolerate the bowel preparation well, some may find it more difficult than others.

“If you experience regular bouts of constipation, you may have a bit of a sluggish bowel and could benefit from starting a clear liquid diet 48 hours before your colonoscopy instead of 24,” Dr. Auteri says. “For everyone else, the best advice is to avoid very heavy foods leading up to the start of your bowel prep.”

There are two other screening options – stool tests and imaging tests.

Stool tests involve taking multiple samples of your stool and sending them off to a lab. They will be tested for traces of blood and genetic material associated with colorectal cancer. While these tests can often identify colorectal cancer, they aren’t as effective at identifying precancerous polyps (especially when compared to colonoscopy). In other words, these tests are good at identifying colon cancer, but not very good at preventing colon cancer.

CT scans (virtual colonoscopy) can show growths and polyps that would be identified during a colonoscopy; however, individuals still need to cleanse their colon with a bowel prep ahead of the scan. Also, if polyps are identified during the scan, the patient will need to undergo a colonoscopy (with another bowel prep) to have them removed.

“No one enjoys the bowel preparation, but colonoscopy is truly the best tool we have for preventing colorectal cancer,” Dr. Auteri says. “We know that people might feel uncomfortable or embarrassed about the colonoscopy process, but we have tried to make the entire experience more patient-friendly. This is an important part of your health, and your care team will make you feel comfortable throughout the entire process.”

The Colon Cancer Screening Act passed by Congress provides insurance coverage for screening colonoscopy by most carriers. You should speak to your insurance provider to make sure you are covered for the screening.