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What is a Colonoscopy? Everything You Need to Know

A colonoscopy is a medical exam that doctors recommend to detect anomalies in the large intestine using an instrument called colonoscope, which is a large flexible tube of about one centimeter in diameter, equipped with a small video camera device.

The following are basic considerations on what a colonoscopy means and things you should do before and after the examination.

“Colonoscopy is the only nonsurgical procedure for directly viewing and often treating problems of the lower digestive tract. Colonoscopy can detect problems in their earliest, most treatable stages.”1

Specialists perform a colonoscopy to determine if there is a colorectal anomaly. “A colonoscopy exam lets a doctor closely look at the inside of the entire colon and rectum to find polyps or signs of cancer. Polyps are small growths that over time can become cancer. The doctor uses a flexible, hollow, lighted tube about the thickness of a finger that has a tiny video camera on the end. This tube, called a colonoscope, is gently eased inside the colon and sends pictures to a TV screen. Special instruments can be passed through the colonoscope to remove small polyps or take tissue samples if needed.”2

Colonoscopy has a high incidence in the US. “Colonoscopy is the most commonly performed endoscopic procedure in the United States and is the preferred method to screen for colorectal cancer.”3

Frequently, patients have a colonoscopy before a colostomy, since the acceptance of ostomy surgery is generally difficult for a patient.

A colonoscopy can help identify polyps in the colon that could become cancerous. “Your digestive system — made up of your mouth, food tube, stomach, bowels, and other organs — helps you break down and absorb food. The last part of your bowels, the large intestine (or the colon), is a hollow tube that helps you absorb water and pass stool and other wastes from your body. Your colon, like other parts of your body, can get cancer. There is no single cause for colon cancer, but nearly all colon cancers begin as non-cancerous polyps. A polyp is a small growth on the surface of your colon that can turn into cancer. Removing polyps may prevent you from getting colon cancer. If polyps have already become cancerous, catching them early increases your chance of surviving or being cured of colon cancer.”4


Polyps and Colonoscopy
Polyps and Colonoscopy

Why do Doctors Recommend a Colonoscopy?

Doctors recommend a colonoscopy when the patient experiences symptoms like abdominal pain and variations in the defecation frequency. Also, if lab tests show blood in stool/urine, or anemia.

“You may have been advised to undergo this investigation of your large bowel to try and find the cause for your symptoms, help with treatment, and if necessary, to decide on further investigation.”5

Doctors usually suggest a colonoscopy exam every ten years for people over fifty to identify the disease on time “One out of every 16 Americans will get colon cancer. Most people survive colon cancer if it is caught early, and only 5 percent of people survive colon cancer if it is caught late.

You may be at higher risk for colon cancer if: 

  • You are older than 45-50 
  • You have had polyps before 
  • Someone in your family has had polyps 
  • You have a family history of colon cancer or polyps 

You may also be more likely to get colon polyps if you: 

  • Eat a lot of fatty foods 
  • Smoke 
  • Drink alcohol 
  • Do not exercise 
  • Weigh too much 

Please talk to your doctor about how you can reduce your risk for colon cancer.”5

Where are Colonoscopies Performed?

“Colonoscopies may be done in a doctor’s office, hospital, clinic, or surgery center. The tests are typically done in a private room.”6

How to Prepare for The Test

Previous to the exam, the doctor must require certain lab tests. Knowing the patient’s general health conditions is equally important for the diagnosis. Inform the doctor about any current treatment or medications and particular health disorders, such as diabetes or allergies. Heart and lung conditions require checking, and a pregnancy test for women.

The procedure also requires clearing the colon of solid matter, usually with enemas or magnesium citrate. For at least 3 days before the exam, the doctor may suggest basing the diet on fluids: soup, water, energizing liquids, fruit juices like apple juice (avoid prune and orange juice), lemonade and herbal tea.


Preparing for Colonoscopy
Preparing for Colonoscopy


 What is a Bowel Prep?

“Bowel prep is a process to clean out the colon as much as possible so the doctor can see the inside clearly and get good pictures. The prep may include eating a special diet, drinking up to a gallon of liquid laxatives, medicines, and sometimes enemas that make you go to the bathroom a lot. You may also be instructed to stop taking certain over-the-counter or prescription medications up to a week before the test.

Preparing for The Investigation 

It is necessary to have clear views of the lower bowel. 

Two Days Before your Appointment 

You will need to be on a low fiber diet and considerably increase your fluid intake. A diet sheet is included with the laxative sent to you.

One Day Before 

You should take clear fluids only (no solid food) e.g. glucose drinks, Bovril, black tea and coffee with sugar, clear soups and fruit jelly. 

In addition, you will need to take a laxative which should have arrived with this booklet along with clear instructions on how to administer it. If you have any queries do not hesitate to contact the endoscopy unit and someone will assist you.

On the Day of the Examination 

You may continue taking clear fluids until you attend for your appointment.”7

How to Know when Bowel Prep is Complete?

“The stool coming out should look like the stuff you are eating and drinking — clear, without any particles. You know you’re done when the stool coming out is yellow, light, liquid, and clear — like urine.”8

Consult your doctor about medications for blood thinning, such as aspirin, ibuprofen and similar (if you are taking them), since they can stop the natural blood clotting effect and could increase bleeding after the procedure.

What about the Medication? 

“Your routine medication should be taken. If you are taking iron tablets you must stop these one week prior to your appointment. If you are taking stool bulking agents you must stop these two days prior to your appointment. 


If you are diabetic controlled on insulin or medication, please ensure the Endoscopy department is aware so that the appointment can be made at the beginning of the list.


If you are taking anticoagulants phone for information if you think you have a latex allergy.”9

What Happens in The Procedure?

The doctor will ask the patient to lie down on the left side, and later, apply a sedation method. In due time, the specialist will insert the colonoscope through the rectum to approach to the other final section of the large intestine to allow examination of the colon. The doctor will examine the inner surface of the intestine to detect polyps (large and irregular tissue outgrowths) or any other type of anomalies.

Generally, the doctor takes small samples of tissue to do biopsy tests to discard health conditions, such as cancer. When confirming the presence of polyps, the specialist could remove it during the procedure.  A polyp can last up to fifteen years without being carcinogenic.

Also, injected air may pass through the colonoscope to blow the intestine and increase visibility, but it will also increase bowel movement. It may cause cramps, but breathing deeply and slowly will allow the abdominal muscles to relax and reduce discomfort.

Intravenous Sedation 

“The sedation and a painkiller will be administered into a vein in your hand or arm which will make you slightly drowsy and relaxed but not unconscious. You will be in a state called cooperative sedation. This means that, although drowsy, you will still hear what is said to you and therefore will be able to follow simple instructions during the investigation. Sedation makes it unlikely that you will remember anything about the examination. 

Whilst you are sedated, we will monitor your breathing and heart rate so changes will be noted and dealt with accordingly. For this reason, you will be connected by a finger probe to a pulse oximeter which measures your oxygen levels and heart rate during the procedure. Your blood pressure may also be recorded.”10

The exam should not last more than an hour. Then, the patient will rest in the recovery room until partially recovering from the sedation. For some patients, half an hour is enough, others may need additional hours before discharge.

Colonoscopy Risks 

“Lower gastrointestinal endoscopy is classified as an invasive investigation and because of that it has the possibility of associated complications. These occur extremely infrequently; we would wish to draw your attention to them and so, with this information, you can make your decision. The doctor who has requested the test will have considered this. The risks must be compared to the benefit of having the procedure carried out. The risks can be associated with the procedure itself and with the administration of the sedation.

The main risks are of mechanical damage:

  • Perforation (or tear in the bowel wall) risk approximately 1 for every 1,000. An operation is nearly always required to repair the hole. The risk of perforation is higher with polyp removal.
  • Bleeding may occur at the site of biopsy or polyp removal (risk approximately 1 for every 100-200 examinations where this is performed). Typically minor in degree, such as bleeding may either simply stop on its own or if it does not, be controlled by cauterization or injection treatment.
  • Pain – Usually this procedure is well tolerated. It is common to experience short-lived discomfort; however, a small percentage of patients may experience pain with this procedure.”11

Discharge Process

After the procedure, you will need to recover for about 30-60 minutes to let the sedative wear off. You may feel some gas during your recovery caused by the air used to inflate your colon. Try taking a walk to help relieve the bloated feeling.12

The patient can return home immediately after leaving the recovery room; however, he or she will be dizzy and require assistance to return home. Therefore, the patient should bring the company to the medical procedure.

Once home, the patient could experience minor abdominal pain, cramps, and flatulence. Following a normal diet including plenty of fluid is appropriate unless the doctor contraindicates it.  However, if you have severe pain in the abdomen, fever or continuous bleeding, inform the doctor should immediately.

The Results

“Your doctor will tell you the results of your colonoscopy either before you leave for home, or within a few days after the procedure. If your problem was treated during the exam, your doctor may give you special instructions to follow. 

If a biopsy was performed, allow several days for the results. If necessary, further studies or treatments may be recommended.”14

How Often Do Patients Require a Colonoscopy?

“If nothing is found, you can go up to 10 years without another test. People older than 75 should talk with their health care provider about if they should keep getting screened. If something is found, you may need more frequent tests or treatment.

The colonoscopy itself takes about 30 minutes. Patients are usually given medicine to help them relax and sleep while it’s done. If so, you will not be allowed to drive afterward, so someone you know must come with you and drive you home. You’ll also have to plan to stay home the day of the test until the drugs wear off.”15

Most people recover quickly and leave shortly after the exam. They can return to their usual routines, including driving and working, the day after colonoscopy.

Call your doctor if you have abdominal pain, high fever, or bleeding.”16

Generally, a colonoscopy will offer a diagnosis and suggest treatment without additional surgical procedures. However, if the result of a biopsy and other tests indicate that a health disorder is present, acceptance of ostomy surgery may be complicated and require psychological and therapeutic assistance. The patient and family should seek specialists from different disciplines to obtain help in the recovery process.



María Laura Márquez
13 March, 2019

Written by

María Laura Márquez, general doctor graduated from The University of Oriente in 2018, Venezuela. My interests in the world of medicine and science, are focused on surgery and its breakthroughs. Nowadays I practice my more:

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