Diagnose and Detection of Colonoscopy


Colonoscopy is a diagnostic technique that allows doctors to examine the lining of the colon. Colonoscopy is performed by specially trained doctors and is often used as a screening tool for colon cancer. The test is done with an instrument called a colonoscope, which is inserted into the rectum and through the colon. When examining the colon, doctors look for polyps and other abnormal lesions. 

The following sections describe colonoscopy in more detail:

Colonoscopy Instruments

The instrument used during colonoscopy is called a colonoscope. It is a long, flexible tube that is inserted into the rectum. Colonoscopes have a light source and a tiny camera that allows doctors to see the inside of the colon on a video screen. Doctors can also take pictures of abnormal lesions or document the entire process, providing a long-term record that can be examined and reviewed if necessary.  

The colonoscope tube includes a channel through which the doctor can pump air into the colon, which inflates the colon and allows a better view of the lining of the colon. Doctors can also insert instruments through the channel into the colon to obtain tissue samples, remove polyps, inject solutions, or burn (cauterize) tissue. For example, if a polyp is found in the colon, a ring of wire called a “snatch” will be passed through the tube and used to remove the polyp, a procedure called a polypectomy. In some cases, a mild electric current will be passed through the catheter to cauterize the tissue to prevent bleeding.  

what to expect


the exam Before the exam, the patient will change into a gown and receive an injection to minimize discomfort. This medicine may make the patient drowsy for several hours. Before surgery begins, patients will likely need to sign a clearance form stating that they understand what the test involves. Note: The anesthesiologist should be notified if the patient regularly takes narcotic pain relievers such as Percodan®, Percocet®, or codeine. 

How it feels

Although colonoscopy is relatively painless, it can be uncomfortable. Patients can take mild sedatives to help them relax. When the colonoscope is inserted into the colon, the air is pushed into the patient through the tube, so the patient may feel the need to have a bowel movement. This feeling is normal, but if it persists, the doctor should be notified so the patient can be given more medication to help them relax. 

After the exam After the

exam, the patient will be placed on the colonoscopy table on his or her left side, which is a comfortable cushion. If anesthesia is used, a small oximeter probe will be placed on the patient’s fingertip to measure pulse rate and respiratory function during the exam. The probe is not invasive and does not cause any pain. In some cases, a narrow oxygen tube may be used to provide a small amount of oxygen to the patient. 


For colonoscopy to be effective and accurate, the colon must be very clean so that the colonoscope can pass through without being blocked by feces, and there must be no solids or liquids present that would obscure the camera’s view. The activities that the patient does before the examination will directly affect the results of the colon examination. To prepare for surgery, most patients will be asked to:

  • Stop using iron pills or other iron-containing medicines, as iron can change the color of the lining of the colon.
  • Take laxatives and enemas prescribed by your doctor. These treatments cause smoother stools that make the imaging process easier.
  • Take a 5-minute walk every ten minutes while you’re on a laxative.
  • Avoid solid foods and opaque liquids.
  • Drink only light liquids such as black coffee, tea, water, clear soups, and fruit juices without pulp. Eat only soft foods like JELL-O®, but don’t eat red foods as they can affect the colon lining.

On the day of the test, the patient may be asked to not eat at all or to eat only light, non-alcoholic fluids. Patients who have diabetes or are taking blood thinners may have different instructions, they should follow a different approach and should consult their doctor for specific instructions on preparing for the test.

In rare cases, phosphate laxatives can cause kidney damage in healthy older adults, people with high blood pressure, arteriosclerosis or heart disease, and people with chronic kidney disease. Patients who fall into this category can use a special form of cleaning solution. 

Patients should wear loose, comfortable, easy-to-remove casual clothing, as a gown will likely be provided. Patients should also leave jewelry and valuables at home.  



When the patient is ready, the doctor will lubricate the opening in the rectum, insert the colonoscope, and guide it through the length of the colon. Your doctor will examine the colon wall carefully, looking for abnormalities. During this procedure, air can also be drawn through the colonoscope to inflate the colon, which makes it easier for the doctor to see all the nooks and crannies. Air may cause abdominal fullness, but not pain. Abdominal cramps and pressure are normal. As the patient passes through the colonoscope, further guidance of the tube into the colonoscope may be requested.  

In some cases, the entire colon cannot be examined. This can be caused by:

  • Tissue outside the colon is blocking the path
  • Scars from past abdominal surgery
  • Severe diverticulosis  

If colonoscopy is unsuccessful in seeing the entire colon, additional procedures, such as barium enema x-rays, may be required. 


This process usually lasts 20-60 minutes. Colonoscopy is an outpatient procedure in most cases, so the patient can go home after the procedure is complete. However, if the patient was sedated during the test, they should be sent home. The patient should rest and relax for a day until the effects of the drug wear off. It is normal to feel bloated or gas for a few hours after a colonoscopy, and walking can help relieve this unpleasant feeling. It is normal to have a small amount of blood on the first bowel movement after the test. However, patients should seek medical attention if they have repeated bleeding, repeated abdominal pain, or a fever of 100 degrees Fahrenheit (37.8 degrees Celsius) or higher. It is also important to alert your doctor if you notice severe abdominal swelling (distention) after a colonoscopy.  

Colonoscopy results

Normal colon polyps colon cancer

Colonoscopy allows doctors to examine the entire lining of the colon for abnormalities, including intestinal inflammation, ulcers, bleeding, diverticulitis, colitis, colon polyps, and tumors. Negative – the doctor found nothing unusual. The patient may not need another colonoscopy for several years. Positive – Doctors find suspicious diseases. Patients need to be tested more frequently. If some small polyps (1 cm or smaller) are found, depending on other risk factors, the patient may not need a colonoscopy for 5-10 years. If many large polyps or polyps with precancerous cells are found, the patient is advised to have a colonoscopy every 3-5 years. If an abnormality is found in a biopsy after colonoscopy, the doctor may decide to remove it or take a tissue sample (biopsy) for analysis. A specially trained doctor, called a pathologist, examines the tissue with a microscope and confirms the diagnosis. A biopsy can help determine the nature of the tissue (benign or malignant) and help doctors decide whether abnormalities need to be removed. Use forceps to cut the colon tissue slices and slice forceps. Alternatively, the doctor may decide to brush the lining of the colon to assess suspicious areas of abnormality. In this case, a small nylon brush is passed through the center of the colonoscope, rubbing against the lining of the colon, and removing a small tissue sample. No matter which type of surgery is performed, the patient will not feel pain. Remember: Just because a doctor decides to do a biopsy, doesn’t mean cancer is suspected. Biopsies can also help diagnose other problems, such as inflammation and ulcers. If tissue is removed during a colonoscopy, a follow-up meeting can be scheduled for the patient and doctor to discuss the results.

Possible disadvantages

Colonoscopy is an effective way to view the colon, but this test has disadvantages:

Ineffective detection

Sometimes colonoscopy is not effective in examining the entire colon. If the colon is dirty or blocked, the doctor may not be able to examine the entire colon. This can lead to missing exceptions. In these cases, a barium enema or virtual colonoscopy may also be required. An older study from 1997 showed that colonoscopy failed to detect the entire colon in 10-15% of cases, and lesions were missed in 10-20%. 4

Possible side effects

In most cases, a colonoscopy will not cause any side effects, but they may occur.

  • Colonoscopy may cause pain and anxiety in some patients. These patients may be given some form of sedative/anesthetic to reduce this feeling. Side effects including drowsiness, nausea, and/or pain at the injection site are possible whenever sedatives/anesthetics are used.
  • Colonoscopy or colon biopsy can cause damage to the colon. A 1997 study showed that a tear in the lining of the colon occurs in 1 in 500-1000 cases.
  • Colonoscopy is expensive ($500-1000) and three times more expensive than barium enemas. Check with your insurance provider about coverage for this test.

Virtual colonoscopy

Virtual colonoscopy is another colon cancer screening technique. Unlike traditional colonoscopies, virtual colonoscopies use a computed tomography (CT) scanner and computer graphics to create a three-dimensional image of the colon. A radiologist analyzes the images to find abnormalities.


A virtual colonoscopy is more comfortable than a traditional colonoscopy because it does not require sedation and does not require inserting the colonoscope into the rectum. It also reduces virtual colonoscopy time (only 15-20 minutes) and enables abnormal examination of organs around the colon.


Virtual colonoscopy does have some disadvantages compared to traditional colonoscopy. Doctors cannot remove polyps or take tissue samples from suspicious areas. If lesions are found, a routine colonoscopy may be required to further investigate the abnormality. In addition, virtual colonoscopy does not provide information about mucosal detail and color, which are useful for the characterization of lesions.

Like all detection methods, virtual colonoscopy is not 100% effective at detecting disease. 

Preparing for a virtual colonoscopy


This preparation method is similar to a traditional colonoscopy. Before the examination, the patient must clear the stool in the colon. Additionally, oral contrast is administered the day before the exam to improve image quality.

virtual colonoscopy

A small enema tip is inserted into the patient’s rectum to introduce air into the colon; this is the only invasive part of the exam. The rest of the exam consists of a series of X-rays taken while the patient is comfortably lying on his back and stomach. 

Except for a momentary feeling of abdominal cramping or gas pushing from the air into the colon, the test is simple and painless. The exam is also quick, as no anesthesia is required, and the patient can resume normal activities immediately after the virtual colon exam. Colon perforation is not risky because the test is not invasive.  

Traditional colonoscopy vs virtual colonoscopy

A 2003 study compared the performance of CT virtual colonoscopy with conventional optical colonoscopy in 1233 asymptomatic adults (mean age 57.8 years). The results are summarized as follows:

Polyps 6 mm in diameter or larger:

  • Polyps 10 mm in diameter or larger:
  • Conventional colonoscopy: sensitivity 87.5%
  • Virtual colonoscopy: 93.8% sensitivity
  • Polyps 8 mm in diameter or larger:
  • Conventional colonoscopy: 91.5% sensitivity
  • Virtual colonoscopy: 93.9% sensitivity
  • Conventional colonoscopy: sensitivity 92.3%
  • Virtual colonoscopy: Sensitivity 88.7%

The specificity of virtual colonoscopy was 96% for polyps at least 10 mm in diameter, 92.2% for polyps at least 8 mm in diameter, and 79.6% for polyps at least 6 mm in diameter. Two of the polyps were malignant, and both were detected by virtual colonoscopy. However, one was missed by optical colonoscopy.

Leave a Reply