colonoscopy colonoscopy colonoscopy (/ˌkɒləˈnɒskəpi/) or coloscopy (/kəˈlɒskəpi/) is the endoscopic examination of the large bowel and the distal part of the small bowel with a ccd camera or a fiber optic camera on a flexible tube passed through the anus. it can provide a visual diagnosis (e.g., ulceration, polyps) and grants the opportunity for biopsy or removal of suspected colorectal cancer lesions. not to be confused with colostomy. colonoscopycolonoscopy being performedicd-9-cm45.23meshd003113ops-301 code1-650medlineplus003886 colonoscopy can remove polyps smaller than one millimeter. once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not. colonoscopy is similar to sigmoidoscopy—the difference being related to which parts of the colon each can examine. a colonoscopy allows an examination of the entire colon (1,200–1,500 mm in length). a sigmoidoscopy allows an examination of the distal portion (about 600 mm) of the colon, which may be sufficient because benefits to cancer survival of colonoscopy have been limited to the detection of lesions in the distal portion of the colon. a sigmoidoscopy is often used as a screening procedure for a full colonoscopy, often done in conjunction with a fecal occult blood test (fobt). about 5% of these screened patients are referred to colonoscopy. virtual colonoscopy, which uses 2d and 3d imagery reconstructed from computed tomography (ct) scans or from nuclear magnetic resonance (mr) scans, is also possible, as a totally non-invasive medical test. virtual colonoscopy does not allow therapeutic maneuvers such as polyp and tumour removal or biopsy, nor visualization of lesions smaller than five millimeters; if a growth or polyp is detected using ct colonography, it would require removal during a standard colonoscopy. surgeons have used the term pouchoscopy to refer to a colonoscopy of the ileo-anal pouch. medical uses conditions that call for colonoscopies include gastrointestinal hemorrhage, unexplained changes in bowel habit and suspicion of malignancy. colonoscopies are often used to diagnose colon polyp and 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 that calls for a colonoscopy, usually along with an esophagogastroduodenoscopy (egd), even if no obvious blood has been seen in the stool (feces). 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 diverticulosis, inflammatory bowel disease (crohn's disease, ulcerative colitis), colon cancer, or polyps. colonic polypectomy has become a routine part of colonoscopy, allowing quick and simple removal of polyps during the procedure, without invasive surgery. colon cancer screening colonoscopy is one of the colorectal cancer screening tests available to people in the us who are 45 years of age and older. the other screening tests include flexible sigmoidoscopy, double-contrast barium enema, computed tomographic (ct) colongraphy (virtual colonoscopy), guaiac-based fecal occult blood test (gfobt), fecal immunochemical test (fit), and multitarget stool dna screening test (cologuard). subsequent rescreenings are then scheduled based on the initial results found, with a five- or ten-year recall being common for colonoscopies that produce normal results. people with a family history of colon cancer are often first screened during their teenage years. among people who have had an initial colonoscopy that found no polyps, the risk of developing colorectal cancer within five years is extremely low. therefore, there is no need for those people to have another colonoscopy sooner than five years after the first screening. some medical societies in the us recommend a screening colonoscopy every 10 years beginning at age 50 for adults without increased risk for colorectal cancer. research shows that the risk of cancer is low for 10 years if a high-quality colonoscopy does not detect cancer, so tests for this purpose are indicated every ten years. colonoscopy screening is associated with approximately two-thirds fewer deaths due to colorectal cancers on the left side of the colon, and is not associated with a significant reduction in deaths from right-sided disease. it is speculated that colonoscopy might reduce rates of death from colon cancer by detecting some colon polyps and cancers on the left side of the colon early enough that they may be treated, and a smaller number on the right side. many of these left-sided growths would have been detected by a sigmoidoscopy procedure. since polyps often take 10 to 15 years to transform into cancer in someone at average risk of colorectal cancer, guidelines recommend 10 years after a normal screening colonoscopy before the next colonoscopy. (this interval does not apply to people at high risk of colorectal cancer or those who experience symptoms of the disease.) although widely touted in the us as the "gold standard" of colon cancer screening, there are few studies of colonoscopy as a screening tool. most of the potential benefits of colonoscopy have been extrapolated from randomized trials of the sigmoidoscopy. the large randomized pragmatic clinical trial nordicc was the first published trial on the use of colonoscopy as a screening test to prevent colorectal cancer, related death, and death from any cause. it included 84,585 healthy men and women aged 55 to 64 years in poland, norway, and sweden, who were randomized to either receive an invitation to undergo a single screening colonoscopy (invited group) or to receive no invitation or screening (usual-care group). of the 28,220 people in the invited group, 11,843 (42.0%) underwent screening. a total of 15 people who underwent colonoscopy (0.13%) had major bleeding after polyp removal. none of the participants experienced a colon perforation due to colonoscopy. after 10 years, an intention-to-screen analysis showed a significant relative risk reduction of 18% in the risk of colorectal cancer (0.98% in the invited group vs. 1.20% in the usual-care group). the analysis showed no significant change in the risk of death from colorectal cancer (0.28% vs. 0.31%) or in the risk of death from any cause (11.03% vs. 11.04%). to prevent one case of colorectal cancer, 455 invitations to colonoscopy were required. the confirm trial, a randomized trial on colonoscopy vs. fit is currently ongoing. recommendations the american cancer society recommends, beginning at age 45, both men and women follow one of these testing schedules for screening to find colon polyps and/or cancer: flexible sigmoidoscopy every 5 years, or colonoscopy every 10 years, or double-contrast barium enema every 5 years, or ct colonography (virtual colonoscopy) every 5 years yearly guaiac-based fecal occult blood test (gfobt) yearly fecal immunochemical test (fit) stool dna test (sdna) every 3 years medicare coverage in the united states, medicare insurance covers the following colorectal-cancer screening tests: colonoscopy: average risk — every 10 years beginning at age 50, high risk — every 2 years with no age restriction flexible sigmoidoscopy — every 4 years beginning at age 50 double-contrast barium enema: average risk — every 4 years beginning at age 50, high risk — every 2 years (ct) colongraphy: not covered by medicare gfobt: average risk — every year beginning at age 50 fit: average risk — every year beginning at age 50 cologuard: average risk — every 3 years beginning at age 50 risks about 1 in 200 people who undergo a colonoscopy experience a serious complication. perforation of the colon occurs in about 1 in 2000 procedures, bleeding in 2.6 per 1000, and death in 3 per 100,000, with an overall risk of serious complications of 0.35%. in some low-risk populations screening by colonoscopy in the absence of symptoms does not outweigh the risks of the procedure. for example, the odds of developing colorectal cancer between the ages of 20 and 40 in the absence of specific risk factors are about 1 in 1,250 (0.08%). the rate of complications varies with the practitioner and institution performing the procedure, and other variables. perforation the most serious complication is generally gastrointestinal perforation, which is life-threatening and in most cases requires immediate major surgery for repair. fewer than 20% of cases may be successfully managed with a conservative (non-surgical) approach. a 2003 analysis of the relative risks of sigmoidoscopy and colonoscopy brought to attention the risk of perforation after colonoscopy is approximately double that after sigmoidoscopy (consistent with the fact that colonoscopy examines a longer section of the colon), a difference that appeared to be decreasing. bleeding bleeding complications may be treated immediately during the procedure by cauterization using the instrument. delayed bleeding may also occur at the site of polyp removal up to a week after the procedure, and a repeat procedure can then be performed to treat the bleeding site. even more rarely, splenic rupture can occur after colonoscopy because of adhesions between the colon and the spleen. anaesthesia as with any procedure involving anaesthesia, other complications would include cardiopulmonary complications such as a temporary drop in blood pressure and oxygen saturation usually the result of overmedication, and are easily reversed. anesthesia can also increase the risk of developing blood clots and lead to pulmonary embolism or deep venous thrombosis. (dvt) in rare cases, more serious cardiopulmonary events such as a heart attack, stroke, or even death may occur; these are extremely rare except in critically ill patients with multiple risk factors. in rare cases, coma associated with anesthesia may occur. bowel preparation dehydration caused by the laxatives that are usually administered during the bowel preparation for colonoscopy also may occur. therefore, patients must drink large amounts of fluids during the day of colonoscopy preparation to prevent dehydration. loss of electrolytes or dehydration is a potential risk that can even prove deadly. in rare cases, severe dehydration can lead to kidney damage or dysfunction under the form of phosphate nephropathy. other virtual colonoscopies carry risks that are associated with radiation exposure. colonoscopy preparation and colonoscopy procedure can cause inflammation of the bowels and diarrhea or bowel obstruction. during colonoscopies where a polyp is removed (a polypectomy), the risk of complications has been higher, although still low at about 2.3 percent. one of the most serious complications is postpolypectomy coagulation syndrome, which occurs following about 1% of colonoscopies with electrocautery polypectomy. it results from a burn injury to the wall of the gastrointestinal tract and causes abdominal pain, fever, elevated white blood cell count and elevated serum c-reactive protein. treatment consists of intravenous fluids, antibiotics, and avoiding any oral intake of food, water, etc. until symptoms improve. risk factors include right colon polypectomy, large polyp size (>2 cm), non-polypoid lesions (laterally spreading lesions), and hypertension. bowel infections are a potential colonoscopy risk, although rare. the colon is not a sterile environment; many bacteria that normally live in the colon ensure the well-functioning of the bowel, and the risk of infections is minimal. infections can occur during biopsies when too much tissue is removed and bacteria protrude in areas they do not belong to, or in cases when the lining of the colon is perforated and the bacteria get into the abdominal cavity. infection may also be transmitted between patients if the colonoscope is not cleaned and sterilized properly between tests. minor colonoscopy risks may include nausea, vomiting or allergies to the sedatives that are used. if medication is given intravenously, the vein may become irritated. most localized irritations to the vein leave a tender lump lasting a number of days but going away eventually. the incidence of these complications is less than 1%. on rare occasions, intracolonic explosion may occur. a meticulous bowel preparation is the key to prevent this complication. signs of complications include severe abdominal pain, fevers and chills, or rectal bleeding (more than half a cup or 100ml). procedure preparation the colon must be free of solid matter for the test to be performed properly. for one to three days, the patient is required to follow a low fiber or clear-liquid-only diet. examples of clear fluids are apple juice, chicken and/or beef broth or bouillon, lemon-lime soda, lemonade, sports drink, and water. it is important that the patient remains hydrated. sports drinks contain electrolytes which are depleted during the purging of the bowel. drinks containing fiber such as prune and orange juice should not be consumed, nor should liquids dyed red, purple, orange, or sometimes brown; however,