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Figure 4: Colonoscopic view showing recurrance of cancer at the site of an anastamosis
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Colonoscopy is a useful investigation in the patient with suspected colorectal cancer. It permits visualisation of the lining of the rectum and colon and the terminal ileum. If suspicious areas are seen they may be biopsied. Polyps may be removed for histological examination.

The colonoscope is a flexible tube about 2 m in length. The operator can see what the end is looking at. Fibreoptics carry light from a light source down the scope to the tip. The light reflects off the inside of the bowel and is collected by a charge coupling device (CCD) integrated circut. The information from the CCD chip is carried back up the scope to be processed and displayed on a monitor. There are two wheels on the hand piece of the scope and two buttons. The two wheels move the tip of the scope back and forth and up and down respectively. Movement in either or both of these axes can be reduced by a lock. One of the buttons (blue button; blue is for BLOW) insufflates gas, it is a valve attached to a pump with variable pressure, the other button (red button) is attached to a vacuum pump for suction. The scope also carries a channel through which the endoscopist can pass various instruments.

The advantages of colonoscopy are;

The disadvantages of colonoscopy are;

Colonoscopy is the investigation of choice in a patient with altered bowel habit or rectal bleeding who is suspected of having colo-rectal cancer. It is also indicated; investigation of lower abdominal and left iliac fossa pain, screening for colo-rectal cancer in people with a strong family history of colo-rectal cancer, surveillence of the residual colon following resection for cancer, investigation of anaemia (particulary if the FOB test is positive), disease follow up (polyps, stricture, Crohn's, ulcerative colitis), diagnosis of patients with ischaemic colitis post aortic surgery, diagnosis of Cl. difficle colitis, colonoscopic de-rotation of sigmoid volvulus, colonoscopic decompression of acute colonic pseudo-obstruction.

* Read more about:Acute colonic pseudo-obstruction
Colonoscopy is contraindicated if the patient is suspected of having a possible perforation in the colon or if a perforation may be easily percipitated by insufflation of gas, for instance in suspected acute diverticulitis and in patients with suspected large bowel obstruction.

next up previous index Surgical Topics
Next: Barium Enema Up: Investigation Previous: Faecal Occult Blood (FOB)   Index
Adrian P. Ireland