Colonoscopy is a minimally invasive endoscopic examination of the large colon and the distal part of the small bowel. It is done with a fiber optic camera fixed on a flexible tube, which is passed through the anus.
The procedure allows for accurate diagnosis and treatment of colon abnormalities without the need for a major operation.
It is possible to do a virtual colonoscopy. This uses 3D imagery reconstructed from computed tomography (CAT) scans. This is a non-invasive medical test.
Colonoscopy is similar but not the same as sigmoidoscopy. Sigmoidoscopy allows the doctors to view only the final part of the colon. Colonoscopy allows a complete examination of the colon.
What is it used for?
This procedure can provide a visual diagnosis for amongst other things ulceration, abnormal growths, and polyps. It can also provide the opportunity for tissue samples (biopsies) to be collected from suspected lesions.
The procedure is also used to determine the presence of colon cancer, colitis (ulcerative or crohn's), diverticulosis and diverticulitis, chronic diarrhoea and constipation.
It may also be used to look for causes of unexplained changes in bowel habits as well as to evaluate symptoms like abdominal pain, rectal bleeding, and weight loss.
Other uses include to examine gastrointestinal haemorrhage, unexplained changes in bowel habit and to diagnose inflammatory bowel disease.
Colonscopy can be done along with an EGD (gastroscopy), to investigate unexplained drop in hematocrit, which normally signifies anaemia.
Colonoscopy Preparation & Diet
Your colon needs to be empty for the colonoscopy to be thorough and safe. Preparation for the procedure involves taking a liquid diet for 1 to 3 days in advance.
The liquid diet should be clear. It should not contain food colourings. Foods you can take in preparation of colonscopy include:
Thorough cleansing of the bowel is needed before this procedurein order to achieve accurate results and for a better view. To assist in cleansing, you may be asked to take a laxative the night before the procedure.
It is also likely that you will be asked to give yourself an enema. An enema is done by inserting a bottle with water and a mild soap in your anus to clean out the bowels.
This procedure is generally performed on an outpatient basis.
The patient is given sedation intravenously. Agents such as midazolam or pethidine are used. Most people will receive a combination of these two drugs. This is usually between 1-4 mg IV midazolam, and 25 to 125 mg IV pethidine.
The patient normally lies on his left side and is given a digital rectal examination. This examines the tone of the sphincter to determine if preparation has been sufficient.
The endoscope is then passed though the anus up the rectum, the sigmoid colon, the descending, transverse and ascending colon, the cecum, and the terminal ileum. The endoscope bends to allow the doctor to move it around the curves of your intestines.
The endoscope also has a movable tip and multiple channels for instrumentation, air, suction and light.
The bowel is occasionally filled with air to enhance visibility. Biopsies (tissue samples) are regularly taken for examination.
Suspicious lesions may be cauterised, treated with laser light or cut with an electric wire for purposes of biopsy. In addition, the doctor can remove most abnormal growths in your colon such as polyps. Polyps are growths in the lining of the bowel.
Medication can be injected to control bleeding lesions. The tissue removal and treatments to stop bleeding generally do not cause any pain.
It is normal to feel mild cramping during the procedure. This can be reduced by taking several slow and deep breaths.
On average, the procedure takes 30 minutes. After the procedure, some recovery time of up to 2 hours is allowed to let the sedative wear off.
Generally, health care facilities require that you be accompanied by someone who can help you get home after the procedure.
Colonoscopy Risks and Side Effects
Bloating and distension may occur for about an hour after the exam until the air is expelled.
On the odd occasion, some people may experience severe abdominal pain, fever, bloody bowel movements, dizziness, or weakness after the procedure. Your doctor should be able to help should you experience these.
A small proportion of patients suffer a perforation. This is a medical emergency and may require immediate surgery.
Post colonoscopy bleeding and sedation reactions are also possible side effects.Excessive bleeding may occur upon the removal of a large polyp.
However, full recovery by the next day is normal and expected. You may then return to your regular activities. The risk of serious complications is as low as 0.2%.