Flat colonic adenomas in Malaysia: Fact or fancy?

BACKGROUND: Some two-thirds of colorectal carcinomas arise from adenomatous polyps, and as such, screening by colonoscopy and polyp removal should significantly reduce colorectal cancer. This has not been the case, as evidenced by recent studies, which revealed that endoscopy failed to prevent up to 50% of all subsequent carcinomas. Flat or depressed adenomas, frequently reported from Japan but rarely elsewhere, might explain the 'missed carcinomas.' Detection of flat adenomas has not been previously reported from Malaysia. METHODS: In the present prospective study, 426 consecutive patients underwent colonoscopic examination between March 1997 and January 2000, for a variety of bowel symptoms. The examinations were performed by an experienced endoscopist using a standard colonoscope and methylene blue dye spraying technique. Macroscopically, flat adenomas were defined using the criteria proposed by Sawada. RESULTS: Twenty-nine adenomas were identified in 12 patients, of which 15 were polypoid and 14 were flat, with no depressed lesions. Eight polypoidal lesions and all the flat adenomas contained mild or moderate areas of epithelial dysplasia. Seven severely dysplastic polyps were identified. One Duke's A polypoidal cancer and two advanced carcinomas were also found. All the severely dysplastic lesions and Duke's A carcinomas were found in polyps greater than 10 mm in mean size. The flat adenomas were all less than 5 mm in size. CONCLUSIONS: A significant proportion of colonic adenomas in Malaysian patients appear as small flat lesions, which could easily be missed during endoscopy. Increased recognition and treatment of flat adenomas among colonoscopists is warranted.     

Predictors of advanced proximal neoplasia in persons with abnormal screening flexible sigmoidoscopy.

BACKGROUND & AIMS: The relationship between distal and proximal colonic findings is uncertain. Thus, there is no consensus on which findings on screening flexible sigmoidoscopy should trigger colonoscopy. METHODS: We analyzed data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial to assess the relationship between distal and proximal colonic findings. RESULTS: A total of 8802 subjects had an abnormal baseline sigmoidoscopy and colonoscopy follow-up. Subjects with <10-mm single or multiple tubular adenomas had similar risks for advanced proximal neoplasia as subjects with hyperplastic polyps or other benign lesions (3%-5%). Subjects with large (>or=10 mm), villous, or severely dysplastic distal adenomas had similarly elevated risks for advanced proximal neoplasia (11%-12%). Multivariate logistic modeling showed a significantly increased risk for advanced proximal neoplasia associated with the presence of a large tubular (odds ratio [OR], 2.6; 95% confidence interval [CI], 2.0-3.4) or villous distal adenoma (OR, 2.7; 95% CI, 2.1-3.5) but not with the presence of one (OR, 1.05; 95% CI, 0.8-1.3) or multiple (OR, 0.8; 95% CI, 0.5-1.2) <10-mm tubular distal adenomas. CONCLUSIONS: Among subjects with a polypoid lesion on screening flexible sigmoidoscopy, those with small tubular distal adenomas are at similar risk for advanced proximal neoplasia as those without distal adenomas. Subjects with a large, villous, or dysplastic distal adenoma are at increased risk. A strategy that encourages individuals with small tubular adenomas on sigmoidoscopy to undergo follow-up colonoscopy and excludes those with nonadenomatous lesions is of questionable validity, because both groups are at similar risk for advanced proximal neoplasia.     

Screening for Colon Malignancy with Colonoscopy

Screening of asymptomatic individuals for colon malignancy has been advocated for the past 20 yr in the hopes of reducing colon cancer mortality. Although sigmoidoscopy is an important element of current screening recommendations, the sensitivity of this test in asymptomatic subjects has never been studied. The purpose of this study was to determine the prevalence and location of polyps and cancers in an asymptomatic population by performing full colonoscopy. We wished to assess the sensitivity of screening flexible sigmoidoscopy to 60 cm by determining how many patients with adenomas or cancer had "index" adenomatous polyps in the distal 60 cm. One hundred five healthy male outpatients, over 50 yr old, with negative examinations for occult blood in stools and no prior history of colon pathology, had full colonoscopy. Careful examination of the distal 60 cm was performed, followed by a full colon examination to the cecum. Forty-three patients (41%) had adenomatous polyps, and only 19 of these patients had an index adenomatous polyp in the distal 60 cm. Therefore, the sensitivity of sigmoidoscopy was 44%. The prevalence of adenomas increased with age. Patients were assigned to one of three groups based on the findings in the distal 60 cm. Group 1 (n = 65) had no polyps in the distal 60 cm, but 18 of these patients (28%) had adenomatous polyps in the proximal colon. Among 21 patients with only hyperplastic polyps in the distal 60 cm (group 2), six patients (29%) had proximal adenomas. In group 3, eight of 19 patients (42%) with adenomas in the distal 60 cm also had proximal adenomatous polyps. We conclude that adenomatous polyps are common in asymptomatic men who have negative tests for fecal occult blood. Sigmoidoscopy to 60 cm had a sensitivity of only 44% in this patient population, suggesting that this is an insensitive test for the detection of patients with adenomatous polyps.     

Distal colonic neoplasms predict proximal neoplasia in average-risk, asymptomatic subjects

Flexible sigmoidoscopy has been recommended as a screening method to reduce the incidence of colorectal cancer in asymptomatic, average-risk subjects through the early detection and removal of polyps. However, the association between distal and proximal colonic neoplasia and, hence, the requirement for colonoscopic follow up of screen-detected distal neoplasms is unclear. Our aims were: (i) to evaluate the risk of having proximal neoplasms in those with distal colonic neoplasms; and (ii) to determine whether the risk was dependent on the number, size, histology or morphology of the distal lesions. We prospectively evaluated asymptomatic subjects in a flexible sigmoidoscopy based screening programme. Those with rectosigmoid neoplasia underwent colonoscopy. The number, size, histology and morphology of the polyps were recorded. Advanced lesions were defined as adenomas > 1 cm or with a villous component or severe dysplasia, carcinoma in situ or cancer. Adenomatous polyps were found in 17% (135) of screening flexible sigmoidoscopies. At colonoscopy, up to 30% of subjects with distal colonic neoplasms had synchronous proximal lesions at colonoscopy and up to 20% had advanced proximal lesions. The risk of proximal colonic neoplasia was increased in those with distal sessile colonic neoplasms but appeared independent of distal lesion size, number or morphology. In conclusion, distal colonic neoplasia predicts proximal neoplasia in up to 30% of subjects and these were advanced lesions in up to 20%. We recommend that all subjects with biopsy proven distal colonic neoplasia undergo colonoscopy.     

Efficacy of screening flexible sigmoidoscopy for colorectal neoplasia in asymptomatic subjects

PURPOSE: Although flexible sigmoidoscopy is recommended in patients over age 40 to complement fecal occult blood screening for colorectal neoplasia, the yield of this procedure in asymptomatic, average-risk subjects has varied between studies. In addition, the efficacy of flexible sigmoidoscopy in detecting early curable carcinoma has been the subject of debate. We therefore undertook this study to assess the efficacy, safety, and cost of the procedure for early detection of colorectal neoplasia in asymptomatic subjects. PATIENTS AND METHODS: Flexible sigmoidoscopy with a 60-cm scope was performed in 412 asymptomatic veterans (mean age, 63.2 years). Subjects with positive fecal occult blood and those at increased risk for colorectal neoplasia were excluded. Costs were estimated on the basis of Medicare payments. RESULTS: A mean length of 56.1 cm of sigmoid and descending colon was examined. A total of 132 polyps were detected in 93 subjects (22.6%). Thirty-five percent of the polyps were located at a distance of greater than 30 cm from the anal verge. Of 122 polyps removed, 26% were 1 cm in size or larger. A total of 77 polyps (63%) were adenomas, and six polyps (5%) were carcinomas. Of the six carcinomas detected (two carcinoma in situ, one Astler Coller stage A, two stage B1, and one stage C1), five were in a localized stage and thus potentially curable. The cost of detecting each potentially curable carcinoma was $47,174. No complications from flexible sigmoidoscopy were noted. CONCLUSION: In conclusion, 60-cm flexible sigmoidoscopy is a safe, high-yield procedure for the initial screening of colorectal neoplasia in asymptomatic, average-risk subjects over the age of 50. Because the carcinomas detected were still in an early stage, such screening may improve survival.     

Prevalence of clinically important histology in small adenomas.

BACKGROUND & AIMS: The prevalence of advanced histology in small polyps has become a crucial issue in optimizing colorectal cancer screening strategies, especially in view of the advent of computed tomography colonography. We evaluated the prevalence of advanced histology in small and diminutive adenomas to clarify their clinical importance in terms of malignant potential. METHODS: Data were reviewed retrospectively from 3291 colonoscopies performed on asymptomatic patients found to have an adenoma on screening with flexible sigmoidoscopy a few weeks before the colonoscopy or who had a family history of colorectal cancer. All polyps were excised endoscopically and sent for pathology testing. Specimens with advanced histology were confirmed by a second reading. RESULTS: Of the 3291 colonoscopies performed, 1235 colonoscopies yielded a total of 1933 small or diminutive adenomatous polyps. Advanced histology including carcinoma was found in 10.1% of small (5-10 mm) adenomas and in 1.7% of diminutive adenomas (< or = 4 mm). Carcinoma was found in .9% of small adenomas, and 0% of diminutive adenomas. Of the 107 patients found to have polyps 2-10 mm with advanced histology, 100 (93%) were referred for colonoscopy because of an adenoma found on a recent screening with flexible sigmoidoscopy. Seven patients underwent colonoscopy for a positive family history of colon cancer; all 7 had a single affected first-degree relative older than age 50. CONCLUSIONS: Adenomas 5-10 mm in size harbor pathologically significant histology, and the need for removal of these lesions must be addressed to optimize colorectal cancer prevention.     

Inter-endoscopist variation in polyp and neoplasia pick-up rates in flexible sigmoidoscopy screening for colorectal cancer

BACKGROUND: The Norwegian Colorectal Cancer Prevention study is an ongoing flexible sigmoidoscopy (FS) screening trial for colorectal cancer. Twenty-one thousand average-risk individuals, aged 50-64 years, living in two separate areas in Norway were randomly drawn from the Population Registry and invited to once-only screening flexible sigmoidoscopy. Examinations were performed over 3 years, at 2 centres, by 8 different endoscopists, using the same type of equipment. The aim of the present study was to investigate possible differences between endoscopists in detecting individuals with polyps, adenomas and advanced lesions (adenomas with severe dysplasia and/or villous components and/or size larger than 9 mm and carcinoma) in flexible sigmoidoscopy screening. METHODS: The present trial comprises data from 8822 individuals, aged 55-64 years, who have undergone a flexible sigmoidoscopy. In the study period, all lesions detected by the different endoscopists were registered. Tissue samples were taken from all lesions detected. RESULTS: Detection rates varied significantly between endoscopists, ranging from 36.4% to 65.5% for individuals with any polyp, from 12.7% to 21.2% for any adenoma and from 2.9% to 5.0% for advanced lesions. In a multiple logistic regression model, the performing endoscopist was a strong independent predictor for detection of individuals with polyps (P < 0.001 ), adenomas (P < 0.001) and advanced lesions (P = 0.01). CONCLUSION: Detection rates for colorectal lesions vary significantly between endoscopists in colorectal cancer screening. Establishing systems for monitoring performance in screening programmes is important. Supervised training and re-certification for endoscopists with poor performance should be considered.     

The significance of diminutive colonic polyps found at flexible sigmoidoscopy

In order to determine the importance of identification and follow-up of diminutive colonic polyps (DCPs) (i.e., those less than or equal to 5 mm in diameter), we studied 3006 patients undergoing flexible sigmoidoscopy. DCPs were found in 315 patients (10.5%). Biopsy of these lesions showed them to be nonneoplastic in 187 patients (59.4%) and neoplastic in 128 (40.6%). Overall, 35% of all DCPs found were neoplastic. Gross appearance of the lesions was found to be an unreliable means of predicting their histologic makeup. Of the 128 patients with neoplastic DCPs, 73 underwent further examination with barium enema and colonoscopy. Synchronous lesions were found in 57.5%. In 10 patients, synchronous lesions were of significance, including carcinomas, adenomas greater than or equal to 8 mm in diameter, or severely dysplastic adenomas. We conclude that all DCPs discovered at sigmoidoscopy should be biopsied and in patients in whom DCPs are found to be neoplastic, colonoscopy should be undertaken to search for proximal synchronous lesions.     

Hyperplastic polyps seen at sigmoidoscopy are markers for additional adenomas seen at colonoscopy

Asymptomatic individuals undergoing screening flexible sigmoidoscopy were prospectively studied. Polyps were found in 185 subjects. The endoscopist recorded an opinion on the polyps' histology based on endoscopic appearance. No polyps were removed at sigmoidoscopy. All subjects with rectosigmoid polyps then underwent colonoscopy and polypectomy. Of them, 99 subjects (54%) had at least one rectosigmoid adenoma, 69 (37%) had only hyperplastic polyps, and 17 (9%) had other findings. The endoscopists' opinion of the histopathology of polyps at sigmoidoscopy was correct for 61% of the lesions. Of subjects with adenomatous rectosigmoid polyps, 29% had additional adenomas at more proximal sites. Proximal adenomas were found in 28% of patients with hyperplastic rectosigmoid polyps. Patients with rectosigmoid hyperplastic polyps had the same risk for additional proximal adenomas as patients with rectosigmoid adenomatous polyps.     

Reducing the incidence and mortality of colon cancer: mass screening and colonoscopic polypectomy

Most colon cancers arise from conventional adenomatous polyps (conventional adenoma-to-carcinoma sequence), while some colon cancers appear to arise from the recently recognized serrated adenomatous polyp (serrated adenoma-to-carcinoma theory). Because conventional adenomas and serrated adenomas are usually asymptomatic, mass screening of asymptomatic patients has become the cornerstone for detecting and eliminating these precursor lesions to reduce the risk of colon cancer. Colonoscopy has become the primary screening test because of its high sensitivity and specificity, and the ability to perform polypectomy. Other screening tests include guaiac tests or fecal immunochemical tests (FIT) for fecal occult blood, and flexible sigmoidoscopy. A minimal colonoscopic withdrawal time of 6 minutes is important to maximize polyp detection at colonoscopy. Chromoendoscopy is an experimental technique used to highlight abnormal colonic areas to identify neoplastic tissue and to potentially determine the histology of colonic polyps at colonoscopy based on superficial pit anatomy.     

Inter‐endoscopist variation in polyp and neoplasia pick‐up rates in flexible sigmoidoscopy screening for colorectal cancer

Background: The Norwegian Colorectal Cancer Prevention study is an ongoing flexible sigmoidoscopy (FS) screening trial for colorectal cancer. Twenty‐one thousand average‐risk individuals, aged 50–64 years, living in two separate areas in Norway were randomly drawn from the Population Registry and invited to once‐only screening flexible sigmoidoscopy. Examinations were performed over 3 years, at 2 centres, by 8 different endoscopists, using the same type of equipment. The aim of the present study was to investigate possible differences between endoscopists in detecting individuals with polyps, adenomas and advanced lesions (adenomas with severe dysplasia and/or villous components and/or size larger than 9?mm and carcinoma) in flexible sigmoidoscopy screening. Methods: The present trial comprises data from 8822 individuals, aged 55–64 years, who have undergone a flexible sigmoidoscopy. In the study period, all lesions detected by the different endoscopists were registered. Tissue samples were taken from all lesions detected. Results: Detection rates varied significantly between endoscopists, ranging from 36.4% to 65.5% for individuals with any polyp, from 12.7% to 21.2% for any adenoma and from 2.9% to 5.0% for advanced lesions. In a multiple logistic regression model, the performing endoscopist was a strong independent predictor for detection of individuals with polyps (P?P?P?=?0.01). Conclusion: Detection rates for colorectal lesions vary significantly between endoscopists in colorectal cancer screening. Establishing systems for monitoring performance in screening programmes is important. Supervised training and re‐certification for endoscopists with poor performance should be considered.     

Significance of distal polyps detected with flexible sigmoidoscopy in asymptomatic patients.

BACKGROUND--Colorectal cancer is a frequent cause of death from cancer. To reduce the mortality associated with this disease, regular flexible sigmoidoscopy is recommended. However, the significance of diminutive polyps (adenomatous or hyperplastic) detected during flexible sigmoidoscopy remains controversial, as does the appropriate endoscope length (35 vs 60 cm) for colorectal cancer screening. METHODS--One hundred one consecutive patients with no history of colonic disease, gastrointestinal tract symptoms, or positive results of fecal occult blood testing underwent flexible sigmoidoscopy as part of a colorectal cancer screening program. All patients with distal polyps detected during flexible sigmoidoscopy underwent colonoscopy. RESULTS--More than 25% of these asymptomatic, predominantly male subjects had colonic neoplasms or polyps detected. Fifty percent more lesions could be detected with a 60-cm sigmoidoscope than with a 35-cm sigmoidoscope, and detection of any distal polyp, whether adenomatous or hyperplastic, was associated with at least one proximal colon adenoma in 20% of patients. "Extended flexible sigmoidoscopy" for colorectal cancer screening was well tolerated by patients, as evidenced by insertion to the hepatic flexure in 25% of patients, and provided significantly more information than could be obtained with a 35-cm sigmoidoscope. CONCLUSIONS--Colorectal cancer screening should be performed with a 60-cm flexible sigmoidoscope, and distal colonic polyps or neoplasms will be detected in 25% of asymptomatic patients.     

Flexible sigmoidoscopy may be ineffective for secondary prevention of colorectal cancer in asymptomatic,average-risk men

Asymptomatic men (N=114) 50 years of age or older had screening for colorectal neoplasia with flexible sigmoidoscopy followed by colonoscopy regardless of the sigmoidoscopic result. Our study objective was to determine the prevalence of patients having isolated adenomatous polyps in a proximal colonic segment in the absence of a distal index neoplasm within reach of the sigmoidoscope. Through the combined use of sigmoidoscopy and colonoscopy, adenomatous polyps were detected in 47 of 114 individuals (41%). A total of 88 adenomas was found. Seventeen patients had isolated neoplasms in proximal colonic segments in the absence of distal adenomas. These patients represented 15% of screened subjects (17 of 114) and 20% of individuals who lacked adenomas on sigmoidoscopy (17 of 84). The majority of proximal neoplasms were small (<1.0 cm), tubular adenomas. Flexible sigmoidoscopy may be ineffective for screening asymptomatic men for neoplasia. However, it remains to be determined if a 20% miss rate (for those with a normal sigmoidoscopic examination) is significant and whether small proximal adenomas are worth finding.     

The role of colonoscopy in screening persons with family history of colorectal cancer

Abstract First-degree relatives of colorectal cancer patients are at increased risk for developing colorectal neoplasms. In order to assess the potentiality of colonoscopy screening in this high-risk population, 213 asymptomatic family members (age range 30-69 years, mean 42.8 years) of those patients with colorectal cancer received colonoscopic examination at Chang-Gung Memorial Hospital from April 1992 to May 1994. Twenty-eight persons with 42 lesions (polyps or cancer) were identified, including 28 adenomas, nine hyperplastic polyps and five adenocarcinomas. The positive detection rate was 9.9% for adenoma and 2.3% for cancer. Colorectal neoplasms afflicted males more frequently than females (16.7 vs 5.7%, P < 0.05) and occurred less frequently in those < 40 years of age (5.5 vs 17.2%, P < 0.05). Forty-two per cent of the detected neoplastic lesions were beyond the reach of 60 cm flexible sigmoidoscopy and 36% of adenomas were < 0.5 cm in size and would be missed if patients were screened by air contrast barium enema. Cost analysis revealed that the charges of both screening colonoscopy and screening flexible sigmoidoscopy/air contrast barium enema were approximate. Colonoscopy also has a high acceptability and safety. It appears appropriate to use colonoscopy, rather than flexible sigmoidoscopy or air contrast barium enema, as an initial screening procedure for persons with a family history of colorectal cancer, especially those > 40 years of age.     

Fecal occult blood and flexible sigmoidoscopy screening for colorectal cancer: modeling the impact on colonoscopy requirements and cancer detection rates

AiM: The aim of this study was to estimate the colonoscopy requirements and the likely impact of fecal occult blood and flexible sigmoidoscopy screening on the detection of colorectal cancer by using previously published data. METHODS: Fecal occult blood and flexible sigmoidoscopy screening programs were applied to the 2.04 million subjects aged 50-65 years, at a participation rate of 40%. The following strategies were evaluated: Fecal occult blood testing with colonoscopy follow up of all positive tests; flexible sigmoidoscopy with colonoscopy follow up of all adenomatous polyps; and flexible sigmoidoscopy with colonoscopy follow up of all adenomatous polyps > 10 mm in size. RESULTS: The fecal occult blood program detected 5.6% of all colorectal cancer cases at a rate of 2,914 colonoscopies/percentage of detection of colorectal cancer. The flexible sigmoidoscopy program detected 14% of all colorectal cancer cases at a rate of 8,160 colonoscopies/percentage of detection of colorectal cancer. The flexible sigmoidoscopy program with follow up of adenomatous polyps > 10 mm in size detected 13% of all colorectal cancer cases at a rate of 1,230 colonoscopies/percentage of detection of colorectal cancer. CONCLUSIONS: Flexible sigmoidoscopy screening followed by colonoscopic follow up of adenomatous polyps > 10 mm in size is the most efficient screening strategy in terms of colonoscopies generated and cases of colorectal cancer detected.     

The interval between flexible sigmoidoscopy screening examinations can be expanded beyond five years

BACKGROUND/AIMS: As one of the methods for colorectal cancer screening, asymptomatic average-risk persons aged > or = 50 years are recommended to undergo flexible sigmoidoscopy screening every 5 years. We evaluate whether the interval between examinations can be extended beyond 5 years. METHODOLOGY: A total of 192 asymptomatic average-risk subjects were studied, all of whom had undergone a initial negative examination on a flexible sigmoidoscopy screening at age > or = 50 years and a second examination at least 3 years later. The study population was divided into three groups according to the interval between examinations, which was 3-5 years in Group A, 5-6 years in Group B, and 6-8 years in Group C. RESULTS: The incidence of neoplasms was compared among the three subjects groups, and it was found to be similar: 11/96 (11.5%) in group A, 4/55 (7.3%) in group B, and 5/41 (12.2%) in group C. All detected adenomas were less than 10 mm in diameter, and none contained a villous component or high-grade dysplasia. No cancers were found in the study. CONCLUSIONS: The results suggest that the interval for screening sigmoidoscopy may be extended beyond 5 years in persons showing negative results on an initial examination.     

Case-control study of screening colonoscopy in relatives of patients with colorectal cancer

OBJECTIVES: The efficacy of colonoscopic screening and polypectomy for the prevention of colorectal cancer (CRC) is well accepted but has never been documented in a prospective, controlled study. Screening by sigmoidoscopy has been found to reduce mortality from cancer of the rectum and distal colon. Case-control studies provide an alternative method for determining the efficacy of screening methods. METHODS: Between 1998 and 2000, a total of 40 subjects were found to have CRC (study group) and 160 had a normal colon (control group) among asymptomatic individuals participating in a screening colonoscopy program for a high-risk population of first-degree relatives of CRC patients. We compared these groups for screening by fecal occult blood testing, flexible sigmoidoscopy, barium enema, and colonoscopy in the 10-yr period before the index colonoscopy. RESULTS: Screening colonoscopy was performed in only 2.5% of the case subjects and 48.7% of controls (p < 0.0001), and all screening procedures in 12.5% and 73.7%, respectively (p < 0.0001). A statistically significant difference was also found for screening with fecal occult blood test, but not for flexible sigmoidoscopy or barium enema. Significant adenomatous polyps >1 cm in diameter were detected and removed in 19% of the control group within 10 yr of the index colonoscopy. Six (15%) of the patients in the study group died of CRC. CONCLUSIONS: Screening by colonoscopy can prevent progression to CRC from adenomatous polyps and may reduce the mortality associated with this devastating disease.     

Rectal aberrant crypt foci identified using high-magnification-chromoscopic colonoscopy: biomarkers for flat and depressed neoplasia

BACKGROUND: Aberrant crypt foci may represent preneoplastic lesions in the human colon. The prevalence of aberrant crypt foci detected using magnification chromoscopic colonoscopy is known to follow a stepwise progression from normal subjects to those with exophytic adenomas and colon cancer. No studies have addressed the prevalence of rectal aberrant crypt foci in patients with flat and depressed colonic lesions that cluster within the right hemi-colon and may undergo de novo neoplastic transformation. METHODS: All patients underwent total colonoscopy by a single endoscopist using the Olympus CF240Z magnifying colonoscope. Flat and depressed lesions were diagnosed using targeted indigo carmine chromoscopy. Prior to extubation, pan high-magnification-chromoscopy using indigo carmine was applied to the rectum and the distal 10 cm of mucosa examined using forward and retroflexed views. Aberrant crypt foci were defined as two or more crypts with dilated or slit-like openings that were raised above the adjacent mucosa. Using high-magnification chromoscopic colonoscopy we assessed the prevalence and dysplastic features of aberrant crypt foci in three groups: endoscopically "normal" subjects, patients with flat/depressed adenoma, and flat/depressed cancer. RESULTS: Two thousand five hundred and fifty-nine patients underwent colonoscopy of which 1,000 were eligible for inclusion. The median number of aberrant crypt foci per patient in the endoscopically normal, adenoma, and cancer group was 1 (range: 0-5), 9 (range: 0-22), and 38 (range: 14-64), respectively. The estimated relative risk of dysplastic aberrant crypt foci when comparing the flat adenoma group with the endoscopically "normal" group was 4.68 (95% CI: 2.23-9.91) with the relative risk for flat cancer versus endoscopically normal group being 21.8 (95% CI: 10.9-23.8). Patients with >5 flat adenomas had higher crypt foci densities than those with <5 adenomas (r=0.53; p<0.001). CONCLUSIONS: The number of aberrant crypt foci in normal patients, patients with flat adenoma, and flat cancer follow a stepwise incremental change as previously observed for exophytic adenomas and cancer. Detection of aberrant crypt foci in the rectum may be a useful biomarker for proximal colonic flat neoplasia and could be used at index flexible sigmoidoscopic screening to stratify risk of proximal colonic neoplasia. Patients with dysplastic aberrant crypt foci of high density should receive total colonoscopy.     

A prospective study of the frequency and the topographical distribution of colon neoplasia in asymptomatic average-risk Chinese adults as determined by colonoscopic screening

BACKGROUND: The goal of this study was to determine the frequency of colorectal neoplasia in an asymptomatic Taiwanese population and the topographic distribution of lesions relative to age and gender. METHODS: Colonoscopy was performed in 1846 consecutive asymptomatic adults undergoing a health evaluation in 2003. Neoplastic lesions were considered advanced if they exceeded 10 mm in size, had a villous component, or contained moderately or severely dysplastic tissue or invasive cancer. Lesions at and proximal to the splenic flexure were considered proximal in location; those distal to the splenic flexure were classified as distal in location. RESULTS: Of 1741 (94.3%) patients (1041 men, 700 women; mean 52.5 years) enrolled, 1708 (98.1%) underwent total colonoscopy. Of these patients, 263 (15.4%) had colorectal neoplasia; 51 (3.0%) had advanced lesions. A total of 331 lesions were detected; 125 (37.8%) were proximal in location. Two thirds of patients with proximal advanced lesions (66.7%, 10/15) had no distal lesion. The proportion of patients with proximal or proximal plus distal lesions increased with age ( p = 0.027). CONCLUSIONS: Colonoscopy is an effective primary screening modality for colorectal neoplasia in asymptomatic Chinese patients. Many lesions would be missed, especially in the elderly, if only sigmoidoscopy was used for initial screening.