Colonoscopy: Difference between revisions
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'''Colonoscopy''' is the [[minimally invasive procedure|minimally invasive]] [[endoscopy|endoscopic]] examination of the large [[Colon (anatomy)|colon]] and the distal part of the [[ileum|small bowel]] with a [[fiber optic]] camera on a flexible tube passed through the [[anus]]. It may provide a visual diagnosis (e.g. [[ulceration]], [[Polyp (medicine)|polyp]]s) and grants the opportunity for [[biopsy]] of suspected lesions. [[Virtual colonoscopy]], which uses 3D imagery reconstructed from [[computed tomography]] (CAT) scans, is also possible, as a totally [[non-invasive (medical)|non-invasive]] medical test, although it is not standard and still under investigation. Colonoscopy is similar but not the same as [[sigmoidoscopy]]. The difference between colonoscopy and sigmoidoscopy is related to which parts of the colon each can examine. Sigmoidoscopy allows doctors to view only the final part of the colon, while colonoscopy allows a complete examination of the colon. |
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==Uses== |
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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]]. In older patients (sometimes even younger ones) an unexplained drop in [[hematocrit]] (one sign of [[anemia]]) is an indication to do a colonoscopy, usually along with an [[EGD]] (gastroscopy), even if no obvious blood has been seen in the stool ([[feces]]). |
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[[Fecal occult blood]] is a quick test which can be done to test for microscopic traces of blood in the stool. A positive test is almost always an indication to do a colonoscopy. In most cases the positive result is just due to [[hemorrhoids]]; however it can also be due to [[polyp_(medicine)|polyps]] (which are easily removed during the colonoscopy procedure), [[diverticulosis]], inflammatory bowel disease ([[Crohn's disease]], [[ulcerative colitis]]), or colon cancer. |
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==Procedure== |
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===Preparation=== |
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The days prior to the colonoscopy the patient is given a [[laxative]] preparation (such as [[sodium picosulfate]], [[sodium phosphate]] solution, or a solution of [[polyethylene glycol]] and [[electrolytes]]) and large quantities of fluid and a low fibre or clear fluid only diet. |
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===The investigation=== |
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During the procedure the patient is often given [[sedation]] intravenously, employing agents such as [[midazolam]] or [[pethidine]] (meperidine or Demerol). The average person will receive a combination of these two drugs, usually between 1-4 mg iv midazolam, and 25 to 125 mg iv [[pethidine]]. |
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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 [[Colon (anatomy)|colon]] (sigmoid, descending, transverse and ascending colon, the cecum), and ultimately the [[ileum|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 maximize visibility. Biopsies are frequently taken for [[histology]]. |
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Suspicious lesions may be [[cauterization|cauterized]], 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 20-30 minutes, depending on the indication and findings. |
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After the procedure, some recovery time is usually allowed to let the sedative wear off. Most facilities require that you have a person with you to help get you home afterwards. |
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An advantage of colonoscopy over x-ray imaging or other, less invasive tests, is the ability to perform minor surgery during the test. If a polyp is found, for example, it can be removed by one of several techniques. A snare can be place around a polyp for removal. Even if the polyp is flat on the surface it can often be removed. For example, the following show a polyp removed in stages. |
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1. Polyp is identified.<br>[[Image:Endomucosal_resection_1.jpg]] |
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2. A sterile solution is injected under the polyp to lift it away from deeper tissues.<br>[[Image:Endomucosal_resection_2.jpg]] |
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3. A portion of the polyp is now removed.<br>[[Image:Endomucosal_resection_3.jpg]] |
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4. The polyp is fully removed.<br>[[Image:Endomucosal_resection_4.jpg]] |
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===Risks=== |
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A very small proportion of patients suffer a [[perforation]]. This is a medical emergency and may require immediate [[surgery]]. Post colonoscopy bleeding, infection, and sedation reactions are also possible side effects. |
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This procedure usually requires patient [[sedation]] and has a low (0.2%) risk of serious complications. |
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==See also== |
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*[[Rectal examination]] |
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==External links== |
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* [http://digestive.niddk.nih.gov/ddiseases/pubs/colonoscopy/ Colonoscopy]. Based on public-domain NIH Publication No. 02-4331, dated February 2002. |
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[[Category:Diagnostic gastroenterology]] |
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[[Category:Medical tests]] |
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[[de:Koloskopie]] |
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[[fr:Coloscopie]] |
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[[he:קולונוסקופיה]] |
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[[pl:Kolonoskopia]] |
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