What is a colonoscopy and everything you need to know about this?

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Colonoscopy is usually performed as an elective procedure under mild sedation in an outpatient endoscopy center or ambulatory surgical center. Less commonly, it is performed urgently in a hospital, often for lower GI bleeding.

After the colonoscope is inserted into the rectum, the tube is inserted into the colon so that the medical team can see it on a monitor. This allows them to look for abnormalities such as polyps (growths of tissue), sores (ulcers), inflammation, and bleeding.

In addition to detecting tissue abnormalities, the colonoscope can be used to treat certain problems. For example, tiny instruments can be inserted through the colonoscope to trim and remove polyps. Tissue samples, called biopsies, may also be obtained during a colonoscopy.


Absolute contraindications for a colonoscopy include:

  • recent heart attack
  • hemodynamic instability
  • Peritonitis
  • Recent surgery with colonic anastomosis or bowel injury and repair
  • Known or suspected colonic perforation
  • Fulminant colitis and severe toxic megacolon

potential risks

Potential risks of a colonoscopy include:

  • Bleeding: Bleeding occurs in about 1 in 1,000 colonoscopies and is more likely to occur when a polyp is removed.
  • Infections: Infections are rare after a colonoscopy.
  • Colon Perforation: Colon perforation (a hole in the colon) is rare, but can occur when air is injected into the colon during the procedure to improve visualization. It can also happen if an instrument punctures the intestine. Factors that increase a person’s risk of this condition include increasing age, being hospitalized (in intensive care) at the time of surgery, a history of abdominal pain, and Crohn’s disease.
  • Post-polypectomy syndrome: This syndrome occurs in about 1 in 1,000 colonoscopies and is more likely to occur when electrocoagulation (cautery or burning) is used to stop bleeding at the base of a polyp when it is being removed. Symptoms include fever and abdominal pain.
  • Medication Side Effects: An adverse reaction (for example, nausea or vomiting) or, rarely, an allergy, may occur to pain-relieving or sedative medications used during a colonoscopy.

Purpose of colonoscopy

A Colonoscopy can be performed as a screening test to look for evidence of precancerous polyps or cancer, or as a diagnostic test when certain colon-related symptoms appear.

screening colonoscopy

While most screening tests are done to try to find cancer at its earliest stage (known as early detection), colonoscopy offers something more unique: It can detect and remove a polyp before it has time to become a cancerous tumor.

The American College of Gastroenterology recommends that screening begin at age 45 for those with a medium risk of developing colon cancer. A screening colonoscopy is recommended every 10 years as long as the results are normal.

Screening is recommended at a younger age (and more often) for those who have risk factors for colon cancer, such as:

  • A strong family history of colorectal cancer or certain types of polyps
  • Family history of a hereditary colorectal cancer syndrome, such as familial adenomatous polyposis or Lynch syndrome
  • Personal history of colorectal cancer or certain types of polyps
  • A personal history of inflammatory bowel disease (IBS), such as Crohn’s disease or ulcerative colitis
  • Personal history of radiation to the abdomen or pelvis to treat cancer

In addition to having a colonoscopy every 10 years (or sooner, depending on previous test results and the person’s risk profile), there are other colon cancer screening options, including

  • An annual fecal occult blood test (guaiac test)
  • An annual fecal immunochemical test (FIT test)
  • A stool DNA test every three years
  • Virtual colonoscopy every five years
  • Flexible sigmoidoscopy every five to ten years

Your medical professional may recommend one or the other based on several factors. Insurance coverage for these tests (such as screening tools) may vary depending on your plan and your medical history.

Diagnostic colonoscopy

A diagnostic colonoscopy may be recommended for those who have colon-related symptoms or signs that may indicate an underlying disease process, such as colon cancer, hemorrhoids, diverticular disease, or IBD.

Symptoms and signs that often warrant a diagnostic colonoscopy include:

  • Rectal bleeding
  • A change in bowel habits, such as diarrhea or constipation, that lasts for more than a few days.
  • A change in the color or shape of your stool
  • Tenesmus (feeling of needing to have a bowel movement after having one)
  • Chronic abdominal or rectal pain
  • Unexplained iron deficiency anemia

How to prepare?

Once your colonoscopy is scheduled, your doctor will give you several preparatory instructions, such as

  • Starting a low-fiber diet several days before the procedure
  • Drink only clear liquids the day before the procedure
  • Avoid any liquid with red, purple, or blue dyes (which can stain the colon and interfere with the test)
  • Stop taking certain medications (non-steroidal anti-inflammatory drugs or blood thinners) for a period of time before the procedure, based on your individual bleeding and clotting risks.
  • Arrange for someone to drive you home after the procedure

To thoroughly cleanse your colon, your doctor will have you undergo a bowel preparation, usually with a liquid laxative such as Golytely (polyethylene glycol). Although there are different types of bowel preparations, they all cause several hours of watery diarrhea, so make sure you have easy access to a bathroom.

Surgery day: what to expect?

A colonoscopy takes about 30 minutes to complete.

Here’s a brief summary of what you can expect from start to finish:

  • After changing into a hospital gown, a nurse will take your vital signs and place an IV in your arm or hand.
  • Once in the procedure room, you will be asked to lie on your left side with your knees bent. You will then be given sedatives and pain relievers, either in pill form or through an IV. This type of anesthesia is called “twilight sleep” and is different from general anesthesia. Although many people sleep through the procedure, you may wake up at times. However, you will be very relaxed.
  • When you are sufficiently sedated, the doctor will insert the colonoscope into your rectum and begin advancing the instrument up your colon. To get a clearer view, air will be pumped through the scope to open up your intestinal passage. If you are awake, you may feel some cramping or bloating during this time.
  • If any abnormal regions are seen, they can be biopsied with a special colonoscope tool. If polyps are found, they can be removed with a special wire loop on the colonoscope. You will not feel anything during the biopsy or removal of the polyps.
  • Once the procedure is complete, the medical professional will remove the colonoscope and take you to a recovery area.