Understanding Colonoscopy

A colonoscopy is a procedure that is conducted to examine the lining of the colon, which is also known as the large intestine. During the process, a colonoscope, which is a flexible tube, is inserted into the anus, through the rectum and into the colon. This thin tube, which has a diameter that’s roughly equivalent to that of an average-sized finger, has a built-in light source and lens. As it travels through the colon, it transmits images onto a monitor. The doctor who is performing the colonoscopy is therefore able to take a very close look at the condition of the colon.

When is a Colonoscopy Recommended?

According to the standards of the American Cancer Society, men and women aged 45 and older should have a colonoscopy performed every 10 years, or sooner and more frequent depending on family history and symptoms. That recommendation applies to people who are at average risk for colon cancer. Those with family histories of the disease and other risk factors may need to have colonoscopies performed more regularly. Colon cancer is the third most common cause of death by cancer in the United States, with 150,000 people being newly diagnosed each year and 50,000 dying from it on an annual basis. A colonoscopy may also be recommended in the case of symptoms like chronic diarrhea and bleeding and a change in bowel habits.

Preparing for a Colonoscopy

For a colonoscopy to be useful, the colon must be as clean as possible when the procedure is performed. Therefore, most patients are advised to only consume clear liquids in the 24 hours leading up to the procedure. Furthermore, most patients are instructed to drink a special cleansing solution the day before. In some cases, an oral laxative may also be used to cleanse the colon. It is important to carefully follow the doctor’s instructions to ensure that the procedure is a success the first time.


The vast majority of medications won’t adversely affect a colonoscopy, so there is usually no need to discontinue use prior to having the procedure performed. However, there are a few exceptions. Medications that may pose problems include anticoagulants like heparin and warfarin; iron supplements; insulin; aspirin; clopidogrel; and arthritis medications. Patients should advise their doctors of all medications they are taking. Make sure to tell your doctor if you are allergic to any medications prior to having a colonoscopy performed.

The Process

From start to finish, a colonoscopy may take anywhere from one to three hours. A sedative and/or painkiller is typically administered shortly before the procedure begins to keep patients comfortable and relaxed. You may be asked to lie on your back or side. The colonoscope is then very slowly advanced until it reaches the small intestine. In rare instances, it may not be possible to get all the way to the small intestine. It is then slowly withdrawn. In both directions, the doctor watches the monitor to look for abnormalities. Small amounts of bloating, cramping or pressure may be present, but most patients report little or no discomfort.


In the event that an abnormality is detected, additional evaluation will be required. Another instrument is usually passed through the colonoscope while it’s still in place and used to perform a quick biopsy of the area in question. A biopsy is just a small sample of the lining of the colon. If the colonoscopy has been ordered due to bleeding, an instrument may be passed through the colonoscope and used to cauterize the area, inject medications to control the bleeding or to apply small clips to stop the bleeding. Because you remain conscious through the procedure, your doctor should let you know whether such steps are necessary while it is happening.


With colon cancer, cancer first begins in polyps, which are abnormal growths in the lining of the large intestine. In many cases, polyps are benign, which means that they aren’t cancerous. However, it’s not possible to conclusively tell whether or not a polyp is malignant. Therefore, it is usually removed and then analyzed later.

Whether or not a polyp is apparently malignant, it is typically removed during the colonoscopy. The doctor may remove the polyp or polyps through fulguration, which means that he simply burns them away. Other times, a wire loop is used to remove them. If a polyp is especially large, a wire loop with an electrical current may be used to perform a snare polypectomy. Biopsy instruments are also occasionally used to remove polyps.

What to Expect Following a Colonoscopy

Following a colonoscopy, it’s not unusual to experience cramping or bloating. These symptoms occur due to the excess air that gets into the colon during the procedure and are no cause for alarm. It may take time for the sedative that was administered prior to the colonoscopy to completely wear off, so patients usually have to rest for a while following the procedure. No matter how long you wait, you will need someone to drive you home because sedatives often continue to affect people’s judgment and mobility for a very long time. While waiting, the doctor should come out and explain the results of the colonoscopy. However, you may have to wait for the results of any biopsies before knowing the complete results. It’s generally okay to start eating again immediately after a colonoscopy, but the doctor may impose restrictions on your diet and activities for a short period of time.


It’s extremely unusual to suffer complications from a colonoscopy, and the procedure is considered to be extremely safe. Although they are rare, it’s important to be aware of them because immediate medical attention may be required. Perforations, or tears, in the wall of the bowel sometimes occur. If a biopsy or polypectomy has been performed, small amounts of bleeding may occur for a while after the procedure. Some people experience adverse side effects from the sedatives or painkillers that they are given. If you experience any of the following symptoms following a colonoscopy, seek medical attention immediately: rectal bleeding, fever and chills or severe abdominal pain.

Manhattan Gastroenterology Locations:
Gastroenterology Upper East Side
983 Park Ave Ste 1D
New York, NY 10028
(212) 427-8761
Gastroenterology Midtown
51 East 25th St Ste 407
New York, NY 10010
(212) 533-2400
Gastroenterology Union Square
55 W 17th St Ste 102
New York, NY 10011
(212) 378-9983