19 March 2019 What is a colonoscopy? A colonoscopy is an endoscopic examination that makes it possible to analyse the large intestine and, subsequently, the final part of the small intestine (ileum). This examination is extremely important in the process of screening for bowel cancer or colorectal cancer . Depending on its extent, colonoscopy can be: Left : the analysis only takes in the rectum, sigmoid colon and descending colon; Total : the entire large intestine is analysed: rectum, sigmoid colon, descending colon, transverse colon, ascending colon and blind colon. How is a colonoscopy performed? Colonoscopy is performed with the patient lying on their left side , with their legs bent. A long, flexible tube of about 10 mm in diameter is inserted into the anus. The tube, known as a colonoscope , has a video camera at one end that transmits amplified, high-definition images to a monitor in the room where the scan is being performed. The doctor can then examine the inside of the intestine in detail as the colonoscope passes through. The colonoscope also has components that enable it to painlessly collect tissue fragments (biopsy) and treat various types of lesions (for example, it can remove polyps). Air is introduced into the colon as the colonoscope moves through it; this is necessary in order to distend the colon and enable better visualisation. It may cause some discomfort , although generally it is well tolerated. This examination can be performed under anaesthetic , which significantly reduces the discomfort that may be associated with it. The use of anaesthetic does not mean the patient has to be admitted to hospital , and they will be free to leave the site shortly after the examination has been completed. However, if they choose to have the examination carried out under anaesthetic, the patient should be accompanied by someone who can assist them, if necessary. In what situations is a colonoscopy carried out? It is always for the doctor to decide whether there is a need for a particular test, depending on the individual characteristics of each person and their complaints or illness . Colonoscopy is considered as being the examination of choice for screening and early diagnosis of bowel cancer . Given the high incidence of this disease, ideally all people over the age of 50 should undergo the test. Colonoscopy is usually advised in the following cases: Where there is a family history of bowel cancer; Where a patient shows symptoms of bowel cancer without any other obvious cause; To remove polyps or treat other lesions that are already known about or diagnosed; To clarify doubts arising from other examinations. How long does a colonoscopy take? It takes on average about 15 to 30 minutes to carry out a colonoscopy. However, it may take longer, especially if there is a need for any additional procedures. After completion of an examination performed under anaesthetic, it will be necessary to wait a while until recovery is complete. This period should be spent resting in a place provided specifically for this purpose. The patient may then leave the hospital. Although colonoscopy in itself is not a time-consuming examination, it is advisable for the patient to set aside a whole morning or afternoon for the test , given that it may be carried out under anaesthetic, or that it may cause discomfort if not. What are the limitations of colonoscopy? Colonoscopy is a technique that can miss lesions and diagnoses , even when the examination is carried out correctly. Barium enema and CT colonography can be considered as alternative and/or complementary examinations. However, they are not as informative as colonoscopy and do not allow biopsies or the removal of polyps to be carried out. Are there any side effects, risks or complications associated with colonoscopy? If the test is performed under anaesthetic, the effects usually wear off within a few hours. The introduction of air may result in a sensation of abdominal pressure and lead to flatulence for a few hours. The risks associated with carrying out a colonoscopy are rare, but they exist, as with any other examination in which devices or medicinal products are used. The incidence of these risks varies depending on each individual case and depends on any drugs or additional procedures that may need to be carried out. These risks include: Infection or complication due to pre-existing diseases; Adverse reactions to medicinal products that have been administered; Intestinal perforation (on average, 1 case in 10,000); Bleeding (on average, 1 case in 100), which may in some cases require hospital admittance, surgical treatment and/or transfusion. To reduce the risk of complications it is essential the doctor be informed of allergies, other pre-existing diseases or ongoing treatments . At the hospitals and clinics of the Hospital da Luz network, you can find doctors specialising in gastroenterology who will be able to carry out any examinations necessary for your situation. This article was written with the support of the gastrenterology team from the Hospital da Luz network . The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
