Colonoscopy is a procedure that allows a health care provider to visually examine the inner lining of the large intestine, including the entire colon and rectum.
During the procedure, which is usually performed at an outpatient center, a health care provider inserts a flexible tube called a colonoscope into the rectum, usually while the patient is under sedation.
In addition to helping diagnose, monitor and manage conditions involving the colon and rectum, colonoscopy is important in the detection of colon polyps, which are small, abnormal growths that can occur on the colon wall.
Most polyps are not cancerous. But certain types of polyps in the rectum and colon can develop into colorectal cancer, which is the third leading cause of cancer death in the U.S. That makes it particularly important for older people to undergo colonoscopy every few years to detect and remove polyps before they can potentially become colorectal cancer.
In terms of regular screening, colonoscopy is best known for its use in detecting polyps in the colon and rectum — small growths in the colon wall that can sometimes develop into colorectal cancer if not found and removed.
However, colonoscopy is also useful in diagnosing and monitoring a number of other conditions that can affect the large intestine, including:
Changes in bowel movements
Rectal bleeding
Crohn’s disease
Unexplained weight loss
Diverticulosis, a condition in which small pockets form in the lining of the large intestine
Severe gas pains
Ulcerative colitis
Rectal cancer
Colon cancer
Collecting tissue samples for laboratory study
Most colonoscopies are performed at a hospital or outpatient center, and take about an hour.
The day before the procedure, your health care provider will usually ask you to perform what’s known as bowel preparation. Bowel preparation usually consists of not eating solid food for at least 24 hours and taking strong laxatives on a set schedule to flush feces and food particles from the digestive system, including the rectum and colon.
During the colonoscopy, you will usually be asked to remove your clothing and wear a hospital gown, then lie on your left side on an examination table. Typically, pain medication and a sedative will be administered to help you relax.
There are different types of sedation that may be used during the procedure: anesthesia, which renders the patient fully unconscious, or what’s called “conscious sedation,” which allows you to remain more alert. Most patients will receive general anesthesia, and have no memory of the procedure.
Once the patient is sedated, the doctor inserts a long, flexible instrument called a colonoscope into your rectum. A tiny camera and light at the tube’s tip captures video images that allow the doctor to visually evaluate the entire colon.
After the procedure is done, you’ll be moved to a recovery room. Once the sedation has worn off, most patients can get dressed and then immediately resume their regular activities, including a normal diet of solid food.
Note that after a colonoscopy procedure, it’s normal to experience gas pains and pass gas more frequently than usual for a few hours afterward. Some light bleeding is also normal, especially if the doctor removed polyps or if you had samples of tissue removed.
However, if you experience severe abdominal pain, a fever of 100 degrees or higher, heavy bleeding or see blood clots after a bowel movement, you should contact your doctor immediately.
The answer to when you should begin screenings for colorectal cancer depends on several factors, including your age, the symptoms you are experiencing and your colon cancer risk factors, including family history of colorectal cancer or polyps.
According to guidance from the American Cancer Society, National Cancer Institute and other respected sources, all adults should have their first colonoscopy by at least at age 45. Those with a family history of colon cancer, colon polyps should have their first screening colonoscopy at age 40.
However, if you have episodes of rectal bleeding or pain during a bowel movement, you should talk to your physician about scheduling a colonoscopy no matter what your age, as these may be early signs of a more serious condition.
In most cases, patients will be asked to do what’s known as bowel preparation at least 24 hours before a colonoscopy.
During the bowel prep period, patients are usually asked to not eat solid food, not drink alcohol and follow a clear liquid diet. Always follow your doctor’s dietary instructions carefully, but this special diet during the bowel preparation period can usually include fluids like fat free bouillon, white grape juice, water, ginger ale and other light-colored liquids.
Be especially sure not to drink anything containing red or purple dye during the bowel prep period, as it could mimic the look of abnormal tissue in the colon and rectum.
You’ll likely be asked not to eat or drink anything — including water — after midnight the evening before the procedure. The morning of the colonoscopy appointment, patients are usually asked to take any prescription medicines they take with just a sip of water.
Always follow your doctor’s dietary instructions, but after the procedure, most patients can return to their normal diet and activities immediately.
Don’t wear any unnecessary jewelry to the appointment. Dress in loose fitting clothes and shoes that can be put on and taken off easily, as you’ll likely be asked to disrobe completely and wear a hospital gown during the procedure.
How long a colonoscopy takes to complete depends on the procedure being performed, whether the physician finds any abnormal tissue or polyps during the colonoscopy, and other factors.
Generally, however, a screening colonoscopy for polyps that doesn’t find anything unusual or an unusually large number of polyps should take about an hour, including the time required for the sedative to wear off in the recovery room.
The GI Genius Intelligent Endoscopy Module is a special form of colonoscopy that employs artificial intelligence (AI) to help physicians detect polyps. Hoag is one of the few places to get a colonoscopy in Orange County that employs the GI Genius system.
GI Genius can be very helpful in the detection of polyps called adenomas. In addition to being the type of polyp most likely to become cancerous if not removed, adenomas can be hard to detect during a colonoscopy because they are flat, small and look very much like the normal lining of the colon. Missing a pre-cancerous adenoma during a colonoscopy can increase a person’s risk of what’s called interval cancer — colon cancer that develops in the interval before a patient is scheduled to repeat colonoscopy screening.
A 2020 study found that utilizing the GI Genius system helped health care providers detect 14.4 percent more adenomas in the large intestine during colonoscopy, with an adenoma miss rate below 1 percent. Learn more about GI Genius colonoscopy at Hoag.
Flexible sigmoidoscopy is a diagnostic medical procedure that also utilizes a colonoscope, but only checks the rectum and lower colon (the sigmoid colon).
Virtual colonoscopy (CT colonography) is an alternative method of checking the colon for issues that is less invasive and doesn’t require sedation.
Unlike traditional colonoscopy, in which a doctor inserts a colonoscope into the rectum to view the colon, virtual colonoscopy visualizes the colon by taking CT scans of the abdomen from outside the body. These scans are then combined to create a three-dimensional view of the colon and rectum.
While virtual colonoscopy requires similar steps to prepare the bowel as a traditional colonoscopy, it is sometimes a better choice for those who are frail, don’t want an invasive procedure or have issues that don’t allow them to be sedated.
One major drawback of virtual colonoscopy, however, is that — unlike traditional colonoscopy — CT scans utilize ionizing radiation to create images. If this is a concern, be sure to discuss the pros and cons of the procedure with your physician.
At the Hoag Digestive Health Institute, we’re committed to utilizing the latest and most advanced methods of diagnostic imaging. That includes cutting-edge developments in colonoscopy, like the GI Genius Intelligent Endoscopy Module.
Studies show that this groundbreaking, AI-enabled system is able to detect over 14 percent more adenomas than traditional colonoscopy, helping doctors find and remove more of the type of polyp that’s most likely to become colorectal cancer. Hoag is one of the few programs on the West Coast to utilize this important new breakthrough.
From imaging techniques that let us see further to clinical trials that push the boundaries of what’s possible, Hoag is leading the way to fuller recoveries and better outcomes for every patient