***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE : Polyps are missed during conventional colonoscopy , even with meticulous technique . The aim of this study was to investigate whether a prototype wide angle colonoscope is associated with a reduced miss rate for polyps . METHODS : Two studies were performed . In study 1 , a total of 50 patients underwent back-to-back , same-day colonoscopy by a single examiner with the prototype wide angle colonoscope and with a st and ard colonoscope  , with the order of scopes r and omized . In study 1 , an attempt was made to keep examination time with the two colonoscopes equal . In study 2 , a total of 20 patients were examined , 10 by the same colonoscopist who performed study 1 and 10 by a second colonoscopist . In study 2 , examiners tried to perform the examinations as quickly as accuracy would allow . RESULTS : In study 1 , the miss rate for all polyps was lower with the wide angle colonoscope ( 20 % vs 31 % ; p = 0.046 ) , although the mean examination time with the wide angle instrument was shorter ( 6.75 min vs 7.64 min ; p = 0.0005 ) . There was no significant difference in detection of adenomas . Polyps , including adenomas , were missed in the peripheral endoscopic field more frequently with the st and ard colonoscope . In study 2 , wide angle colonoscopy was associated with reductions in examination time of 25 % and 30 % for the two examiners , respectively . Miss rates were the same for one colonoscopist but were higher for the other colonoscopist when the wide angle instrument was used . CONCLUSION : A prototype wide angle colonoscope did not eliminate polyp miss rates .  Wide angle colonoscopy has the potential to reduce examination time and improve visualization of the periphery of the endoscopic field of view , but improvements in resolution are needed An important determinant in interpreting the results of colorectal polyp chemoprevention trials is the rate of polyps missed during colonscopic examination . We prospect ively examined 90 patients by t and em colonoscopy performed by two alternating examiners . In 69 ( 76.7 % ) patients , 221 neoplastic lesions were documented histologically . Of a total of 58 lesions detected in 31 patients , no neoplastic lesion greater than or equal to 10 mm in size was missed ; 16 % of diminutive ( less than or equal to 5 mm ) neoplastic polyps and 12.3 % of medium-sized ( 6 - 9 mm ) neoplastic polyps were missed by the first examiner . We conclude that an experienced colonoscopist will miss about 15 % of colorectal neoplastic polyps less than 10 mm in size in the setting of adequate bowel preparation . Large ( greater than or equal to 10 mm ) polyps were rarely missed , however , with the " miss " rate in our study equal to 0 , with a 95 % confidence limit of 4.64 % BACKGROUND & AIMS Colonoscopic polypectomy is considered effective for preventing colorectal cancer ( CRC ) , but the incidence of cancer in patients under colonoscopic surveillance has rarely been investigated . We determined the incidence of CRC in patients under colonoscopic surveillance  and examined the circumstances and risk factors for CRC and adenoma with high- grade dysplasia . METHODS Patients were drawn from 3 adenoma chemoprevention trials . All underwent baseline colonoscopy with removal of at least one adenoma and were deemed free of remaining lesions . We identified patients subsequently diagnosed with invasive cancer or adenoma with high- grade dysplasia . The timing , location , and outcome of all cases of cancer and high- grade dysplasia identified are described and risks associated with their development explored . RESULTS CRC was diagnosed in 19 of the 2915 patients over a mean follow-up of 3.7 years ( incidence , 1.74 cancers/1000 person-years ) . The cancers were located in all regions of the colon ; 10 were at or proximal to the hepatic flexure . Although most of the cancers ( 84 % ) were of early stage , 2 participants died of CRC . Seven patients were diagnosed with adenoma with high- grade dysplasia during follow-up . Older patients and those with a history of more adenomas were at higher risk of being diagnosed with invasive cancer or adenoma with high- grade dysplasia . CONCLUSIONS CRC is diagnosed in a clinical ly important proportion of patients following complete colonoscopy and polypectomy . More precise and representative estimates of CRC incidence and death among patients undergoing surveillance examinations are needed BACKGROUND Although tests for occult blood in the feces are widely used to screen for colorectal cancers , there is no conclusive evidence that they reduce mortality from this cause . We evaluated a fecal occult-blood test  in a r and omized trial and documented its effectiveness . METHODS We r and omly assigned 46,551 participants 50 to 80 years of age to screening for colorectal cancer once a year , to  screening every two years , or to a control group .  Participants who were screened su bmi tted six guaiac-impregnated paper slides with two smears from each of three consecutive stools . About 83 percent of the slides were rehydrated . Participants who tested positive underwent a diagnostic evaluation that included colonoscopy .  Vital status was ascertained for all study participants during 13 years of follow-up . A committee determined causes of death . A single pathologist determined the stage of each tissue specimen . Differences in mortality from colorectal cancer , the primary study end point , were monitored with the sequential log-rank statistic . RESULTS The 13-year cumulative mortality per 1000 from colorectal cancer was 5.88 in the annually screened group ( 95 percent confidence interval , 4.61 to 7.15 ) , 8.33 in the biennially screened group ( 95 percent confidence interval , 6.82 to 9.84 ) , and 8.83 in the control group ( 95 percent confidence interval , 7.26 to 10.40 ) . The rate in the annually screened group , but not in the biennially screened group , was significantly lower than that in the control group . Reduced mortality in the annually screened group was accompanied by improved survival in those with colorectal cancer and a shift to detection at an earlier stage of cancer . CONCLUSIONS Annual fecal occult-blood testing with rehydration of the sample s decreased the 13-year cumulative mortality from colorectal cancer by 33 percent BACKGROUND AND STUDY AIMS In spite of scrupulous inspection during routine colonoscopy , small lesions behind the semilunar folds can be situated in blind spots , where they are easily overlooked . The aim of this study was to evaluate the efficacy of total colonoscopy with a transparent cap in identifying such lesions , in comparison with colonoscopy without the cap . PATIENTS AND METHODS In 24 patients with colorectal polyps , t and em colonoscopic procedures were carried out on the same day in r and om order , first without a transparent cap and then with the cap ( without-to-with ) , or first with the cap and then without the cap ( with-to-without ) . The time required for intubation as far as the cecum , the number of polyps detected , and procedure-related complications were recorded . The frequencies of terminal ileal intubation and retroflexion within the rectum were also recorded . RESULTS Total colonoscopy was carried out in all of the patients without any complications . Colonoscopy with a transparent cap ensured good visual fields during insertion and withdrawal of the colonoscope . There were no significant differences in the intubation time to the cecum or in the frequency of terminal ileal intubation between the two procedures . The miss rate for polyps was 15 % in without-to-with t and em colonoscopies , and zero in with-to-without procedures ( P = 0.0125 ) . The diameter of all the missed polyps except for one lesion ( 8 mm ) was less than 5 mm . Retroflexion within the rectum was more difficult using the colonoscope with the cap ( P < 0.0001 ) , and was successful in only one case using the cap . CONCLUSIONS Total colonoscopy with a transparent cap allows inspection of the blind area of the colonic mucosa behind the semilunar folds , with good visual fields . This method is potentially useful for both screening and diagnostic purpose BACKGROUND & AIMS The miss rate of colonoscopy for neoplasms is poorly understood . The aim of this study was to determine the miss rate of colonoscopy by same day back-to-back colonoscopy . METHODS Two consecutive same day colonoscopies were performed in 183 patients . The patients were r and omized to undergo the second colonoscopy by the same or a different endoscopist and in the same or different position . RESULTS The overall miss rate for adenomas was 24 % , 27 % for adenomas < or = 5 mm , 13 % for adenomas 6 - 9 mm , and 6 % for adenomas > or = 1 cm . Patients with two or more adenomas at the first examination were more likely than patients with no or one adenoma detected at the first examination to have one or more adenomas at the second examination ( odds ratio , 3.3 ; 95 % confidence interval , 1.69 - 6.46 ) . Right colon adenomas were missed more often ( 27 % ) than left colon adenomas ( 21 % ) , but the difference was not significant . There was evidence of variation in sensitivity between endoscopists , but significant miss rates for small adenomas were found among essentially all endoscopists . CONCLUSIONS Using current colonoscopic technology , there are significant miss rates for adenomas < 1 cm even with meticulous colonoscopy . Miss rates are low for adenomas > or = 1 cm . The results suggest the need for improvements in colonoscopic technology BACKGROUND : Small adenomas are commonly missed during routine colonoscopy . The aim of this study was to determine whether routine retroflexion in the proximal colon would improve adenoma detection rates . METHODS : One hundred patients underwent colonoscopy from the cecum to the splenic flexure by a gastroenterology fellow , with the removal of all visualized polyps . The cecum was then reintubated and patients were r and omized to a second exam of the proximal colon by an experienced staff physician in either the forward view or a retroflexed view . RESULTS : Two patients were excluded due to a difficult initial cecal intubation . Forty-eight patients were r and omized to forward view and 50 patients were r and omized to a retroflexed view . Retroflexion was successful in the cecum in 60 % , the ascending colon 100 % , and the transverse colon 98 % . The success in retroflexion was determined in part by the type of colonoscope used . If any portion of the retroflexed examination could not be performed , that reexamination was performed in the forward view . The calculated miss rates for all polyps and adenomas among patients r and omized to second examination in the forward view was 36.8 % and 33.3 % , respectively . The calculated miss rate for all polyps and for adenomas among patients r and omized to a second examination in the retroflexed view was 38.1 % and 23.7 % , respectively . There was no difference in miss rates for all polyps or for adenomas ( p = 0.31 ) when the second examination was performed in the forward view versus retroflexed view . CONCLUSIONS : A second examination by retroflexion in the proximal colon did not increase the calculated miss rate relative to that performed by a forward view examination . These results do not support the addition of routine right colon retroflexion to colonoscopy BACKGROUND Accurate measurement of polyp size during colonoscopy is important because of the direct correlation of size with colon cancer . Major studies of colorectal neoplasms have measured polyp size differently . It is also well documented that endoscopists underestimate polyp size frequently . The goal of this prospect i ve study was to determine which one of the five methods of estimating polyp size during colonoscopy is most accurate . METHODS One hundred colon polyps were measured by means of visual estimation , open biopsy forceps methods , linear probe , a ruler immediately after excision , and after fixation in formalin . The size of the polyps measured outside the body immediately after excision was considered the " gold st and ard " against which all measurements were compared . RESULTS Forty-seven polyps were 5 mm or less in diameter , 33 polyps were 5.01 mm to 10 mm , and 20 polyps were more than 10 mm in size . For all polyps the mean difference versus the actual size of the polyps was 3.4 % for linear probe , 6.4 % for visual estimation , and 12.3 % for the forceps . CONCLUSION Measurement of polyp size by linear probe agreed best with the actual polyp size , followed closely by visual estimation . The open biopsy forceps method was the least accurate Aim : To study the availability and quality of  adult and paediatric colonoscopy  in three National Health Service ( NHS ) regions . Method : A prospect i ve four month study of colonoscopies in North East Thames , West Midl and s , and East Anglia . Patients : Subjects undergoing colonoscopy in 68 endoscopy units . Results : A total of 9223 colonoscopies were studied . The mean number of colonoscopies performed over the four month period was 142 in district general hospitals and 213 in teaching hospitals .  Intravenous sedation was administered in 94.6 % of procedures , but 2.2 % and 11.4 % of “ at risk ” patients did not have continuous venous access or did not receive supplemental 
    Output:
    
: Colonoscopy rarely misses polyps ≥10 mm , but the miss rate increases significantly in smaller sized polyps .