A colonoscopy procedure enables a gastroenterologist to look inside your large intestine (colon) and rectum. In most cases, this colonoscopy doctor performs the procedure to detect and prevent colon and rectal cancer. Colonoscopy has become very common, but there are important things everyone should know about preparation, anesthesia options, and recovery.
Colorectal cancer is the third-leading cause of cancer-related death in the United States for both men and women, taking an estimated 53,200 lives in 2020, according to the Centers for Disease Control and Prevention. Fortunately, National Cancer Institute statistics show a 90% five-year survival rate when the cancer is detected early. However, the survival rate drops to 72% when the cancer is not discovered until it has spread to regional lymph nodes, and it plummets to 14% when the cancer has spread to distant sites like the liver or lungs.
Colonoscopy is a type of colorectal cancer screening that is doubly protective because it does more than provide early detection. Because colorectal cancer begins in abnormal growths called polyps, a colonoscopy can prevent the disease by identifying and removing polyps before they turn cancerous.
Colonoscopies are also performed to determine the causes of symptoms such as rectal bleeding, changes in bowel activity, abdominal pain, and unexplained weight loss, as well as to diagnose Crohn’s disease and ulcerative colitis.
The U.S. Preventive Services Task Force recommends beginning some form of colon cancer screening at age 50 for people without a family history of the disease, based on convincing evidence that screening in adults ages 50–75 reduces colorectal cancer mortality. Many professional organizations recommend that screening begin at a younger age for people with a family history of colorectal cancer or other risk factors. Some evidence suggests that Black Americans are at higher risk and should begin screening at age 45.
The task force advises that people who choose a colonoscopy as their screening method should repeat it every 10 years until they turn 75. If polyps are detected during your colonoscopy, you may be advised to repeat the procedure in less than 10 years.
During a colonoscopy, the gastroenterologist inserts a long, thin, flexible tube called a colonoscope into the patient’s rectum. The instrument is equipped with a tiny video camera and light at its tip. The camera sends a video image to a monitor, allowing the doctor to examine the patient’s large intestine. The doctor removes any polyps discovered in the intestine and may remove small pieces of other types of abnormal tissue for further examination.
Before the procedure begins, an IV is placed in the patient’s vein so that medications for sedation can be given quickly. The patient is connected to equipment that monitors heart rate, blood pressure, and oxygen levels. The patient also receives oxygen through the nose.
The colonoscopy procedure usually takes 30–60 minutes, but that does not include the time required for the patient’s preparation and recovery at the hospital or outpatient center. The total time from the patient’s arrival for the appointment to departure typically ranges from two to three hours.
Almost all colonoscopies in the United States are performed with patients under a level of sedation or anesthesia that prevents them from feeling anything. Often, patients are asleep for the entire procedure.
Patients who ask for light sedation are more likely to feel discomfort and perhaps some pain during the procedure. The likelihood increases with no sedation.
Your doctor will provide instructions on changing your diet for a few days before the procedure and cleaning out your bowels the day before, which involves taking a combination of laxatives. The laxatives will cause diarrhea and frequent trips to the bathroom. This colonoscopy prep is essential for allowing your doctor a clear view of your colon during the procedure.
You can make the prep easier for yourself by getting ready for it. Stock items like moist wipes, diaper cream, and clear sodas and low-fiber foods you enjoy. Clear your schedule on preparation days to the extent possible.
Talk with your doctor about any health problems, previous negative reactions to anesthesia, and all prescribed and over-the-counter medicines, vitamins, and supplements you take. Don’t leave anything out. This information affects decisions about safely administering sedation or anesthesia during the procedure and avoiding complications like bleeding from polyp removal. You may be advised to stop taking some medications or supplements or to adjust their dosages in the days before the colonoscopy procedure.
Unless you elect to receive no sedation, you will need to arrange for someone to take you home after the colonoscopy. It can take a while for the sedative to wear off, so it is not considered safe for you to drive, take public transportation on your own, go back to work, or make important decisions that day. You may be advised to avoid driving for 24 hours following the procedure.
Even before reviewing your options, there are some important things to know and do.
- The gastroenterologist will determine your level of sedation, but you have a say in that decision.
- When scheduling your colonoscopy, always ask your doctor what level of sedation or anesthesia is planned. Although many gastroenterologists default to deep sedation, that is not always the case. If you want deep sedation, you may need to request it.
- Your age, medical conditions, and health habits can influence the choice of anesthesia. For example, a patient with heart or lung problems, obesity, or any condition that affects the airway may need to avoid deep sedation.
- The level of sedation you receive and your health history are factors in determining what type of medical professional should administer the sedation during your procedure.
All medications for sedation are administered intravenously (through a vein in your arm). Most patients receive moderate or deep sedation, but there are other options. Your choices include:
- No sedation. Refusing sedation is rare in the United States: Just 2% of colonoscopy patients opted for no sedation, according to a 2016 National Institutes of Health survey. However, some people make this choice because they want to be able to drive themselves home after the procedure, to prevent any potential complications from anesthesia, or to avoid taking the opioids that are often used for light or moderate sedation.
- Minimal or light sedation. Medications such as benzodiazepines and opioids will help you relax, but you will likely remain awake and may feel some pain or discomfort. You’ll be able to understand questions, provide answers, and follow directions.
- Moderate sedation. You will feel drowsy and may even fall asleep during the procedure and not remember it. As with light sedation, benzodiazepines and opioids are most commonly used, but in higher amounts. Compared with deep sedation, this option has a lower risk of lowering your blood pressure or slowing your breathing, but because you may remain awake, you may feel some discomfort.
- Deep sedation. You won’t be completely unconscious, but you’ll sleep through the procedure and probably have no memory of it. The medication commonly used for deep sedation is propofol, which is not an opioid. It acts fast, wears off quickly, and is safe for most patients. Because the drug may lower your blood pressure and slow your breathing, it may not be safe for everyone.
- General anesthesia. This type of anesthesia is not commonly used for colonoscopies, but for patient safety it may be the best option for people who have airway abnormalities or are at high risk for aspiration of stomach contents. This type of anesthetic renders you completely unconscious, and your breathing is impaired, so a breathing tube, ventilator, and inhalation anesthetic are used.
Light or moderate sedation is usually administered by a nurse under the direction of the gastroenterologist, but if you will be receiving deep sedation or general anesthesia, it is important to ask that a anesthesiologist be involved in your care. It is easy to go from deep sedation into general anesthesia (in which breathing is impaired), depending on your age, your medical problems, and the amount of medication needed to cause you to go to sleep. An anesthesiologist is a medical doctor who has the extensive education, training, and experience required to adjust medication dosing during deep sedation and intervene to assist your breathing as needed.
Even under deep sedation, you will not remain asleep for long: That effect usually wears off within 30 minutes of the removal of the IV. You may feel bloated or pass gas for a few hours after the exam, but walking could help relieve the discomfort.
The removal of polyps or tissue samples could cause some light bleeding in your first bowel movement after the procedure. Consult with your doctor if you continue to pass blood or blood clots or if you have persistent abdominal pain or a fever.
Risks are low but do exist. A study completed in 2016 for the U.S. Preventive Services Task Force found four to eight serious complications for every 10,000 colonoscopy procedures. Bleeding and perforation of the colon are the most common complications and usually occur in patients who have polyps removed.
Less common risks include severe abdominal pain or a reaction to the sedative, including breathing or heart problems. Deaths from colonoscopy are very rare.
Anesthesiologists work with your surgical team to evaluate, monitor, and supervise your care before, during, and after surgery—delivering anesthesia, leading the Anesthesia Care Team, and ensuring your optimal safety.