Colonoscopy (from Greek "eidoscopy" meaning" look inside", aka coloscopy) is the use of an endoscope to examine the large intestine, and the distal part of the small intestine, using a camera on a flexible tube, that is passed into the body through the anus.
Virtual colonoscopy (aka CT colonography, or CT pneumocolon) uses 2D (from x-ray) and 3D imagery (from CT or MRI), so is non-invasive. It produces 3D reconstructed endoluminal views of the GI tract, all the way from the rectum all the way to the lower end of the small intestine, and displays it on the screen. It can Dx polyps, diverticulosis, and cancer. The disadvantage is that it does not allow for therapeutic maneuvers, e.g. polyp/tumor removal or biopsy, nor visualization of lesions <5mm.
Indications
Visual diagnosis, e.g. for ulceration, polyps
Removal of lesions, and even Biopsy (i.e. microscopic examination), e.g. of:
Colorectal cancer lesions
Colon polyps, as small as 1mm or even less
The American Cancer Society recommends that for 50yo+, both men and women do a colonoscopy every 5 years
Classification
Colonoscopy, can examine the entire colon (1.2-1.5m)
Sigmoidoscopy,can examine the sigmoid colon (about 0.6m, cf. the whole large intestine in colonoscopy), from the rectum. Flexible sigmoidoscopy uses a flexible endoscope, and rigid sigmoidoscopy uses a rigid device, with the former the preferred procedure
Method
Mechanical bowel preparation is where fecal matter is expelled form the bowel lumen prior to colonoscopy (or other invasive procedure, e.g. surgery), most commonly by using sodium phosphate
Digital rectal exam, to examine the tone of the sphincter and to determine if preparation has been adeqaute
The endoscope is passed through the anus up the rectum, the colon (sigmoid, descending, transverse and ascending colon, cecum), and ultimately the terminal ileum
YouTube video
Patient information
Let's have a journey through the GI tract. What will I see?
We start in at the mouth. We go down the pharynx, the esophagus, into the stomach. From there, we go into the small intestine, the large intestine, and out the anus.
Small and large intestine. What's what ?
The small intestine includes the duodenum, jejunum and ileum. The cecum marks the division between the small and large intestines. The large intestine includes the colon, sigmoid, and later bits (rectum and anal canal).
Side effects
Nausea or vomiting
Allergies to sedatives used
Bleeding → rectal bleeding (>half a cup)
GI perforation → fevers and chills, severe abdominal pain
Epidemiology
Although the reach of sigmoidoscopy are limited, benefits of cancer survival of colonoscopy, have been limited to detection of lesions in the distal portion of the colon
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