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Colonoscopy is the minimally invasive endoscopic examination of the large colon and the distal part of the small bowel with a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy of suspected lesions.
Uses
Indications for colonoscopy include gastrointestinal hemorrhage, unexplained changes in bowel habit or suspicion of malignancy. Colonoscopies are often used to diagnose or rule out colon cancer, but are also frequently used to diagnose inflammatory bowel disease.
Procedure
Preparation
The days prior to the colonoscopy the patient is given laxatives (e.g. macrogol-containing softeners) and large quantities of fluid, causing frequent diarrhea or loose stools, then followed the next morning by enemas, so that the bowels are optimally clean for the examination. Many people find that the preparation for the colonoscopy is more uncomfortable than the procedure itself. On the day before the examination, only a light breakfast can be had, after which only clear fluids are permitted.
The investigation
During the procedure the patient is often sedated intravenously, employing agents such as midazolam or pethidine.
The first step is usually a digital rectal examination, to examine the tone of the sphincter and to determine if preparation has been adequate. The endoscope is then passed though the anus up the rectum, the sigmoid colon, the descending, transverse and ascending colon, the caecum, and the terminal ileum. The endoscope has a movable tip and multiple channels for instrumentation, air, suction and light. The bowel is occasionally insufflated with air to maximise visibility.
Suspicious lesions may be cauterised, treated with laser light or cut with an electric wire for purposes of biopsy. Medication can be injected, e.g. to control bleeding lesions. On average, the procedure takes 30-60 minutes, depending on the indication and findings.
After the procedure, some recovery time is usually allowed for to let the sedative wear off.
Risks
A very small proportion suffers a perforation. This is a medical emergency and requires immediate surgery.
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