Colonoscopy

A colonoscopy is a medical procedure that can save your life by finding and removing growths before they turn into cancer, and it remains the gold standard for colorectal cancer screening and diagnosis.

Table of contents

• What is a colonoscopy?
• Why would you need a colonoscopy?
• When to get screened
• Preparing for your colonoscopy
• What happens during the procedure
• Potential risks and complications
• Therapeutic uses

What is a colonoscopy?

A colonoscopy is an examination of the inside of your large intestine (the lower part of your digestive system), which includes your colon, rectum and anus^[1]. It’s a type of endoscopy, which means that it uses an endoscope—a flexible tube with a lighted camera on the end that’s inserted into your body^[1].

During the procedure, a long, flexible tube called a colonoscope is inserted into the rectum^[2]. The colonoscope passes through your anus and rectum into your colon, and along the way, it sends pictures of the inside of your large intestine to a screen^[1]. A tiny video camera at the tip of the tube allows the doctor to view the inside of the entire colon^[2].

A colonoscopy permits a comprehensive examination of the entire colon, which is typically around 1,200 to 1,500 millimeters in length^[4]. The procedure uses either a CCD camera or a fiber optic camera, which is mounted on the flexible tube^[4].

• Colon
• Rectum
• Anus
• Large intestine

Why would you need a colonoscopy?

A colonoscopy may be preventive, diagnostic or therapeutic—and often, it’s all of these^[1]. Your healthcare provider may advise you to have a colonoscopy for routine cancer screening if you’re at a statistically higher risk of developing colorectal cancer (cancer that starts in the colon or rectum)^[1].

Since anyone can have colorectal cancer at any time without warning or symptoms, screening is the best way to stay ahead of it^[1]. Colorectal cancer often doesn’t cause any symptoms until it’s too advanced to treat effectively^[1].

Some people have colonoscopies because they have symptoms that a healthcare provider must investigate more closely^[1]. A colonoscopy provides a better view of your large intestine than other types of imaging tests that don’t go inside your body^[1].

Symptoms that might require a colonoscopy include unexplained rectal bleeding or discharge, unexplained changes in your bowel habits such as diarrhea or constipation, unexplained persistent abdominal pain, and unexplained weight loss^[1].

Diseases or conditions that a colonoscopy might help diagnose include chronic colitis such as ulcerative colitis or Crohn’s disease, intestinal ischemia and ischemic colitis, diverticulosis and diverticulitis, ulcers and perforations, and large bowel obstructions^[1].

When to get screened

In the United States, colorectal cancer represents the third most frequently diagnosed malignancy and the second leading cause of cancer-related mortality^[3]. Most people will have their first colonoscopy for routine cancer screening^[1].

Statistically, your risk of developing colorectal cancer goes up as you age, which is why the American Cancer Society recommends regular screening at least by the age of 45^[1]. If you’re age 45 or older and at average risk of colon cancer—you have no colon cancer risk factors other than age—your doctor may recommend a colonoscopy every 10 years^[2].

You may be due for a colonoscopy for cancer screening if you are older than 45 and haven’t had one, haven’t had one for 10 years, had tissue removed during your last colonoscopy, have a family history of colorectal cancer, have an inherited disease that raises your risk such as familial adenomatous polyposis (FAP) or Lynch syndrome, or have inflammatory bowel disease^[1].

In the United States, medical insurers and Medicare must cover routine colonoscopy screenings under the Patient Prevention and Affordable Care Act (PPACA)^[1]. These screenings save thousands of lives each year^[1].

Preparing for your colonoscopy

Preparing for your colonoscopy is important because the colon must be cleared of all solid matter so the doctor can see clearly^[6]. If your colon is not clean, your exam may be canceled^[6]. The effectiveness of a colonoscopy depends on how thoroughly the bowel is cleansed before the procedure^[6].

To prep for a colonoscopy, you need to cleanse your digestive system^[20]. The point of preparation is to flush stool from your colon and rectum so your physician can see the walls of both structures clearly^[20]. This makes it easier to find polyps (small growths that can develop into cancer)^[20].

The better the bowel preparation, the higher the chance that the endoscopist can identify and remove polyps, which reduces the risk of future colon cancer^[6]. Good colonoscopy preparation is crucial for maximizing adenoma detection rates^[19].

Your doctor will give you detailed instructions on how to prepare for your colonoscopy^[7]. The most important thing is to clean out your bowels completely^[7]. This enables your doctor to have a clear view of the lining inside your colon during the procedure^[7].

Your physician will prescribe a bowel preparation prior to your scheduled procedure^[6]. Colonoscopy prep involves taking an oral laxative, which triggers bowel movements^[6]. The primary purpose of colonoscopy prep is to clean out the bowels of stool and undigested material^[6].

Up to five days before your colonoscopy, you will need to stop taking certain medications, including iron supplements and aspirin—and anything else your doctor identifies^[7]. Eating smaller portions and low-fiber foods a few days before you plan to do colonoscopy prep can help the evening go smoothly^[16].

The day before a colonoscopy, patients must stick to a liquid diet—that is, no solid foods^[16]. You will need to fast for a day and take a strong laxative to cleanse the bowels^[7].

What happens during the procedure

Most colonoscopies are done under sedation^[7]. Because it involves anesthesiology, you have to recruit a volunteer to drive you home^[7]. Since you will be given anesthesia before the procedure, you will not be able to drive home afterward^[7].

A colonoscopy is typically performed on an outpatient basis^[7]. The doctor inserts a thin, flexible tube with a tiny light and camera attached to it into the rectum and up through the colon^[7]. Photographs or video images of the insides of these organs appear on a monitor, so the doctor can look for growths such as polyps^[7].

The test can also be used to inspect the colon for inflammation, bleeding and ulcers^[7]. If necessary, polyps or other types of abnormal tissue can be removed through the scope during a colonoscopy^[2]. Tissue samples, called biopsies, can be taken during a colonoscopy as well^[2].

Sometimes your doctor might need to take a tissue sample to examine under a microscope in order to make a diagnosis^[1]. They can do that during the colonoscopy^[1]. If your physician sees a polyp, they will remove it during the procedure and then send it to a lab for testing^[20].

Potential risks and complications

While colonoscopy is generally a safe procedure, it does carry some risks. The most serious potential complication is perforation (a tear or hole in the wall of the colon)^[4].

Issues can also arise from general anesthesia used during the procedure^[4]. Additionally, colon preparation can cause electrolyte imbalances in some patients^[4].

After the procedure, you’ll rest until the sedation wears off^[7]. You may experience mild discomfort, but this usually subsides quickly^[7].

Therapeutic uses

Colonoscopy is recognized as the gold standard modality for colorectal cancer screening and diagnosis, and it also serves as a therapeutic intervention through polypectomy (removal of polyps) of lesions with malignant potential^[3].

By facilitating the detection and removal of precancerous polyps, colonoscopy reduces progression to malignancy and improves survival outcomes^[3]. Colorectal cancer can find polyps so that they can be removed before they turn into cancer^[6]. A colonoscopy can also find colorectal cancer early, when the chances of being cured are good^[6].

Removing polyps before they turn into cancer may save your life^[20]. When it is found early, the five-year survival rate for colorectal cancer is about 90%^[20].

Beyond cancer screening, colonoscopy serves as an indispensable tool in the diagnosis and longitudinal monitoring of inflammatory bowel disease, hereditary polyposis syndromes including familial adenomatous polyposis, serrated polyposis syndrome, and Peutz-Jeghers syndrome, as well as managing diverticular disease^[3].

Therapeutic applications extend to colonic stenting for malignant obstruction, endoscopic reduction of sigmoid volvulus and intussusception, preoperative tattooing, intraoperative lesion localization, and evaluation of anastomotic integrity^[3].

Sometimes, a colonoscopy may be done for treatment purposes, such as placing a stent or removing an object in your colon^[2].