Conditions & Investigations



Colonoscopy is a procedure which enables the direct visualisation of the lining of your colon (large intestine). A flexible tube, as thick as your finger, is inserted through the back passage and slowly advanced from the rectum through the entire five to six feet of colon to the caecum where it joins onto the small intestine. The examination can detect abnormalities present in the inner lining of the colon such as a polyp, colon cancer or inflammation. Biopsies (small tissue samples) can be obtained, and most polyps can be removed during a colonoscopy.

Screening for bowel cancer is an important function of colonoscopy. Cancer of the large bowel, also referred to as colorectal cancer, usually develops from a benign precursor, a polyp. The detection and removal of colon polyps which do not usually cause any symptoms will reduce the chances of an individual developing colorectal cancer.

What problems can a colonoscopy detect?

  • Abnormal growths
  • Polyps (precancerous growth)
  • Inflammation
  • Diverticular disease

Colonoscopy is indicated to determine the cause of:

  • rectal bleeding, anaemia,
  • a change in bowel habit
  • abdominal pain
  • persistent diarrhoea
  • screening for colorectal cancer
  • unexplained weight loss
  • anaemia
  • bleeding from the back passage

What are the colon and rectum?

The colon and rectum are the two main parts of the large intestine. Although the colon is only one part of the large intestine, because most of the large intestine consists of colon, the two terms are often used interchangeably. The large intestine is also sometimes called the large bowel.

Digestive waste enters the colon from the small intestine as a semisolid. As waste moves toward the anus, the colon removes water and forms solid stool. The rectum is about 6 inches long and connects the colon to the anus. Stool leaves the body through the anus. Muscles and nerves in the rectum and anus control bowel movements.

What preparation is required for a colonoscopy?

The preparation involves going on a clear liquid diet for 24 hours prior to the procedure. In addition, a strong laxative preparation is taken the day beforehand, following the instructions that are supplied [diet sheet]. The colon should be completely clean for the procedure to be accurate and complete, so it is important to follow the instructions carefully.

How is a colonoscopy performed?

Many patients wish to have a sedative, which is administered with an injection through a drip in the arm. Sedatives help patients stay relaxed and comfortable. While patients are sedated, the doctor and medical staff monitor vital signs. A flexible tube with a video chip on the end (the endoscope), is inserted into the back passage. The tube is thinner than an index finger. The bowel is inflated with air, and so patients may experience some bloating. The tube is slowly moved along the colon so that good views of the inside of the bowel are obtained. The tube travels all the way round to the caecum, which is where the colon (large intestine) is joined on to the small intestine. The test takes approximately 30 minutes.

During the test, biopsies (small tissue samples) are often taken from the wall of the colon, even if it looks normal. There may sometimes be periods of discomfort as the tube goes around bends in the bowel, which usually all settles down once the bend has been passed. In order to make the procedure easier, patients are often asked to change position by rolling on to their back or even right hand side. If a polyp is found, which is a small outgrowth from the lining of the bowel they are removed at the time of the procedure, Whilst most polyps are completely innocent, some may develop into bowel cancer if they are not removed.

After a colonoscopy, patients are moved to a recovery room where they wait about an hour for the sedative to wear off. During this time, patients may feel bloated. Patients will likely feel tired and should plan to rest for the remainder of the day. Unless otherwise directed, patients may immediately resume their normal diet and medications.

Driving is not permitted for 24 hours after a colonoscopy in order to allow sedatives time to completely wear off. Before the appointment, patients should make plans for a ride home.