author/s: Dr Mª del Carmen Peña Cala, Dr Javier Nebreda Duran
It is an internal examination of the colon that uses an instrument called colonoscope consisting of a small camera adhered to a flexible tube. In contrast with sigmoidoscopy, in which only the inferior third of the colon is examined, colonoscopy examines the colon along its entire extension (see animation).
Preparation for the test:
- Prior to the test, it is essential to have cleansed the intestine completely, and in order to do this, the doctor will give you specific instructions that includes: diet with no residue (fibre) and the intake of laxatives.
- The patient can also be asked to stop taking aspirin or other anticoagulant medication during several days before the test.
- Some patients with valvular cardiac disease can receive antibiotics before and after the test to prevent infections.
- Ambulatory patients must have someone to drive them home after the test, as they will feel confused and unable to drive.
How the test is done?
- The patient rests on the left side with the knees flexed towards the thorax.
- An IV is started and a mild pain killer and a sedative are administered endovenously during the procedure.
- Usually, the doctor performs a digital rectal examination to dilate the rectum and to make sure that there are no major obstructions.
- The colonoscope is inseted through the anus and moved gentil upwards to reach the terminal portion of the small intestine.
- Air is insufflated through the colonoscopue to obtain better visualisation. Suction can be used to remove secretions.
- Tissue samples can be taken using small biopsy (see animation) clamps that are introduced through the colonoscope. Any polyps can also be removed with a metallic loop for electrocauterisation and photographs taken.
What you feel during the examination without sedation:
- With the movement of the colonoscope inside, it is likely for the person to experience a pressure and that as air is insufflated or as the colonoscope is moved forward, he or she feels short colicky like pain and some discomfort due to the gas. This pain can be helped by taking slow, deep breaths, which also helps relax the abdominal muscles.
- If the patient is sedated, there is no discomfort whatsoever.
Why is the test necessary?
- To obtain tissue samples for biopsy.
- To assess an unexplainable anaemia.
- To evaluate the presence of unexplainable blood in the faeces, abdominal pain, persistent diarrhoea or abnormalities such as polyps found upon a contrast X-ray (barium enema).
- To determine the type and extensión of inflammatory intestinal disease (ulcerative colitis and Chron´s disease).
- To follow up a previous finding of polyps, cancer of the colon or a familial past history of this sort of cancer.
- Polypectomy: With a “lasso” loop we can cut and remove polyps (see animation).
- Sclerosis of bleeding lesions (with a needle that is introduced through the lumen of the endoscope we can inject substances that stop the bleeding).
- Fulguration with argon beam (gas that in contact with air produces a burn and is used to cauterise bleeding lesions, angiodysplasias, etc.)
- Pneumatic dilations of stenotic areas (with a balloon filled with water or air inside the colon at a controlled pressure).
- Placement of stents in stenotic areas (it is a sort of mesh that is positioned inside the colon) that clear obstruction and allow free passage; for instance, in a case of stenosing cancer of the colon (a type that obstructs the lumen of the intestine) prior to surgery or palliative treatment.
What are the risks?
- Intestinal perforation (orifice) that might require even surgical intervention to sew the orifice (less than 2 per 1,000 examinations).
- Profuse bleeding or persistent bleeding at the biopsy sites or polypectomy (1 out of each 1,000 examinations).
- Adverse reaction to sedatives, causing respiratory depression or low blood pressure (4 out of each 10,000 examinations).
- An infection requiring antibiotic treatment (quite rare).
- Nausea, vomiting, rectal swelling and irritation caused by oral purgatives.
The patient must sign an informed consent form, as with any other invasive medical procedure. In some cases, the effect of the sedative may last for some hours and thus, the patient is advised not to drive or take important decisions during this short period of time. It is recommended to take lots of liquids to replace what was lost due to the laxatives and the fasting.
What is the best test to prevent cancer of the colon?
The best test to prevent cancer of the colon is a total colonoscopy, as it permits a detailed visualisation of the colon and to observe any existing anomaly using a device called colonoscopy (see animation).
How often should I have check ups?
This depends on the familial past history and the cause of the pathology.
For further information, please refer to Secondary prevention.
After what age is an endoscopy necessary?
The standard age recommended to carry out a colonoscopy is 50 years if there is no familial past history of cancer of the colon. If such a past history is present in first-degree relatives (parents, offspring and siblings), the test is recommended after the age of 40 or 15 years before the affected relative is diagnosed.
For further information, please refer to Secondary prevention.
If the endoscopy identifies a polyp, how is it treated?
Normally, during the actual colonoscopy, if a polyp is detected, it can simply be excised on the spot via the same endoscopic route without any further problems. If the polyp is larger or hard to get to, some times it may require surgery to be removed.
How early, after I have had a polyp removed, I need to have a check up?
This depends on the type, characteristics and the size of the polyp removed.
Depending on this data, a follow up colonoscopy is recommended after 6 months and 3-4 years. For further information, please see Tertiary prevention.
If I have suffered from cancer of the colon, how often and what type of check ups do I need to have?
Refer to Tertiary prevention.
- If you have a relative diagnosed with cancer of the colon, you should consult with your digestologist (a specialist consultant in digestive diseases).
- If you need to have a colonoscopy, you should follow your doctor´s instructions strictly prior to the test. This will ensure that at the time of the test, visualisation of the colon will be good and complete.
- Do not wait to be reminded! If you are 50 or over, or 40 but with a family relative with cancer of the colon, you should see your consultant.
- If you bleed through the rectum, do not think, “this is just haemorrhoids”, you should seek medical attention immediately.