The effectiveness of colonoscopy in preventing colorectal cancer (CRC) within opportunistic screening programs has not been clearly established. The aim of this study was to analyze the effectiveness of colonoscopy within an opportunistic screening program using nested case-control study.

Subjects who received a diagnosis of CRC (CG) between the ages of 50 and 90 years were included and matched by age and gender in a 1:5 ratio with patients without CRC diagnosis (COG) during the period 2015 to 2023. Using conditional regression analyses, we tested the association between screening colonoscopy and CRC. Subgroup analyses were then performed for CRC location, endoscopist specialty, and colonoscopy quality.

Of the 134 patients in CG, 19 (14.18%) had a colonoscopy in the preceding 5 years compared with 258 out of 670 (38.51%) in COG (AOR, 0.24; 95% CI: 0.14-0.41). Any colonoscopy was strongly associated with decreased odds for left-sided CRC (AOR, 0.09; 95% CI: 0.04-0.24) but not for right-sided CRC (AOR, 0.58; 95% CI: 0.29-1.17). Only complete colonoscopy (AOR, 0.41; 95% CI: 0.19-0.89) and colonoscopy with satisfactory bowel preparation (AOR, 0.38; 95% CI: 0.15-0.98) were associated with decreased odds for right-sided CRC. No significant differences in colonoscopy outcomes were found when stratifying by endoscopist specialty.

In the setting of an opportunistic screening program, exposure to any colonoscopy significantly reduced left-sided CRC incidence; however, only high-quality colonoscopy was associated with a lower incidence of right-sided CRC. Therefore, every possible effort should be made to optimize the quality and cost-effectiveness of colonoscopy within an opportunistic screening program.

Colon capsule endoscopy as an alternative to colonoscopy for the diagnosis of colonic disease may serve as a less invasive and more tolerable investigation for patients. Our aim was to examine patient-reported outcomes for colon capsule endoscopy compared to conventional optical colonoscopy including preference of investigation modality, tolerability and adverse events. A systematic literature search was conducted in Web of Science, PubMed and Embase. Search results were thoroughly screened for in- and exclusion criteria. Included studies underwent assessment of transparency and completeness, after which, data for meta-analysis were extracted. Pooled estimates of patient preference were calculated and heterogeneity was examined including univariate meta-regressions. Patient-reported tolerability and adverse events were reviewed. Out of fourteen included studies, twelve had investigated patient-reported outcomes in patients who had undergone both investigations, whereas in two the patients were randomized between investigations. Pooled patient preferences were estimated to be 52% (CI 95%: 41-63%) for colon capsule endoscopy and 45% (CI 95%: 33-57%) for conventional colonoscopy: not indicating a significant difference. Procedural adverse events were rarely reported by patients for either investigation. The tolerability was high for both colon capsule endoscopy and conventional colonoscopy. Patient preferences for conventional colonoscopy and colon capsule endoscopy were not significantly different. Procedural adverse events were rare and the tolerability for colon capsule endoscopy was consistently reported higher or equal to that of conventional colonoscopy.

The landscape of gastrointestinal endoscopy continues to evolve as new technologies and techniques become available. The advent of image-enhanced and magnifying endoscopies has highlighted the step toward perfecting endoscopic screening and diagnosis of gastric lesions. Simultaneously, with the development of convolutional neural network, artificial intelligence (AI) has made unprecedented breakthroughs in medical imaging, including the ongoing trials of computer-aided detection of colorectal polyps and gastrointestinal bleeding. In the past demi-decade, applications of AI systems in gastric cancer have also emerged. With AI's efficient computational power and learning capacities, endoscopists can improve their diagnostic accuracies and avoid the missing or mischaracterization of gastric neoplastic changes. So far, several AI systems that incorporated both traditional and novel endoscopy technologies have been developed for various purposes, with most systems achieving an accuracy of more than 80%. However, their feasibility, effectiveness, and safety in clinical practice remain to be seen as there have been no clinical trials yet. Nonetheless, AI-assisted endoscopies shed light on more accurate and sensitive ways for early detection, treatment guidance and prognosis prediction of gastric lesions. This review summarizes the current status of various AI applications in gastric cancer and pinpoints directions for future research and clinical practice implementation from a clinical perspective.

The aim of this study was to evaluate if integrating whole-body PET/CT with CT colonography (PET/CTC) improves the preoperative diagnosis of obstructive colorectal cancer (CRC).

We prospectively included 47 consecutive patients (18 women and 29 men; mean age, 71 ± 14 years) suspected of having CRC by optical colonoscopy, which was not completed due to obstructive masses. To perform PET/CTC, a small caliber Foley catheter was inserted to distend the colon with CO2 insufflations. Polyps measuring 10 mm or larger were considered as high risk of malignancy. All findings were histologically confirmed.

Colorectal cancer was localized in the sigmoid (n = 21), rectum (n = 7), rectosigmoid junction (n = 5), ascending (n = 7), descending (n = 5), and transverse (n = 2) colon. All tumors showed FDG uptake (mean ± SD SUVmax, 20.02 ± 9.9) including one synchronic tumor (SUVmax, 10.46). Forty-seven polyps were histologically confirmed as smaller than 10 mm (n = 35) and 10 mm or larger (n = 12). All 12 polyps 10 mm or larger showed FDG uptake (SUVmax range, 3.08-19.5), but only one smaller than 10 mm could be identified by PET. Pathological lymph nodes were diagnosed in 17/47 cases after surgical removal with a sensitivity and specificity for CTC and PET/CTC of 71% and 97% and 59% and 100%, respectively. Liver metastases were confirmed in 9 patients and in 4/9 along with lung metastases (n = 2) or implants (n = 2), showing a sensitivity and specificity for CTC of 89% and 100% and both 100% for PET/CTC.

PET/CTC is a reliable technique for staging CRC and diagnosing synchronous tumors. In this series, PET/CTC was not able to identify small polyps but showed potential use for ruling out 10 mm or larger polyps at high risk of malignancy.

In case of incomplete colonoscopy, several radiologic methods have traditionally been used, but more recently, capsule endoscopy was also shown to be accurate. Aim of this study was to compare colon capsule endoscopy (CCE) and CT colonography (CTC) in a prospective cohort of patients with incomplete colonoscopy.

Consecutive patients with a previous incomplete colonoscopy underwent CCE and CTC followed by colonoscopy in case of positive findings on either test (polyps/mass lesions ≥6 mm). Clinical follow-up was performed in the other cases to rule out missed cancer. CTC was performed after colon capsule excretion or 10-12 h postingestion. Since the gold standard colonoscopy was performed only in positive cases, diagnostic yield and positive predictive values of CCE and CTC were used as study end-points.

100 patients were enrolled. CCE and CTC were able to achieve complete colonic evaluation in 98% of cases. In a per-patient analysis for polyps ≥6 mm, CCE detected 24 patients (24.5%) and CTC 12 patients (12.2%). The relative sensitivity of CCE compared to CTC was 2.0 (95% CI 1.34 to 2.98), indicating a significant increase in sensitivity for lesions ≥6 mm. Of larger polyps (≥10 mm), these values were 5.1% for CCE and 3.1% for CTC (relative sensitivity: 1.67 (95% CI 0.69 to 4.00)). Positive predictive values for polyps ≥6 mm and ≥10 mm were 96% and 85.7%, and 83.3% and 100% for CCE and CTC, respectively. No missed cancer occurred at clinical follow-up of a mean of 20 months.

CCE and CTC were of comparable efficacy in completing colon evaluation after incomplete colonoscopy; the overall diagnostic yield of colon capsule was superior to CTC.

NCT01525940.

Colorectal cancer screening is thought to be an effective tool with which to reduce the mortality from colorectal cancer through early detection and removal of colonic adenomas and early colon cancers. In this article, we review the history, evolution, and current status of imaging tests of the colon-including single-contrast barium enema, double-contrast barium enema, computed tomographic (CT) colonography, and magnetic resonance (MR) colonography-for colorectal cancer screening. Despite its documented value in the detection of colonic polyps, the double-contrast barium enema has largely disappeared as a screening test because it is widely perceived as a labor-intensive, time-consuming, and technically demanding procedure. In the past decade, the barium enema has been supplanted by CT colonography as the major imaging test in colorectal cancer screening in the United States, with MR colonography emerging as another viable option in Europe. Although MR colonography does not require ionizing radiation, the radiation dose for CT colonography has decreased substantially, and regular screening with this technique has a high benefit-to-risk ratio. In recent years, CT colonography has been validated as an effective tool for use in colorectal cancer screening that is increasingly being disseminated.

Cecal intubation is one of the goals of a quality colonoscopy; however, many factors increasing the risk of incomplete colonoscopy have been implicated. The implications of missed pathology and the demand on health care resources for return colonoscopies pose a conundrum to many physicians. The optimal course of action after incomplete colonoscopy is unclear.

To assess endoscopic completion rates of previously incomplete colonoscopies, the methods used to complete them and the factors that led to the previous incomplete procedure.

All patients who previously underwent incomplete colonoscopy (2005 to 2010) and were referred to St Paul's Hospital (Vancouver, British Columbia) were evaluated. Colonoscopies were re-attempted by a single endoscopist. Patient charts were reviewed retrospectively.

A total of 90 patients (29 males) with a mean (± SD) age of 58 ± 13.2 years were included in the analysis. Thirty patients (33%) had their initial colonoscopy performed by a gastroenterologist. Indications for initial colonoscopy included surveillance or screening (23%), abdominal pain (15%), gastrointestinal bleeding (29%), change in bowel habits or constitutional symptoms (18%), anemia (7%) and chronic diarrhea (8%). Reasons for incomplete colonoscopy included poor preparation (11%), pain or inadequate sedation (16%), tortuous colon (30%), diverticular disease (6%), obstructing mass (6%) and stricturing disease (10%). Reasons for incomplete procedures in the remaining 21% of patients were not reported by the referring physician. Eighty-seven (97%) colonoscopies were subsequently completed in a single attempt at the institution. Seventy-six (84%) colonoscopies were performed using routine manoeuvres, patient positioning and a variable-stiffness colonoscope (either standard or pediatric). A standard 160 or 180 series Olympus gastroscope (Olympus, Japan) was used in five patients (6%) to navigate through sigmoid diverticular disease; a pediatric colonoscope was used in six patients (7%) for similar reasons. Repeat colonoscopy on the remaining three patients (3%) failed: all three required surgery for strictures (two had obstructing malignant masses and one had a severe benign obstructing sigmoid diverticular stricture).

Most patients with previous incomplete colonoscopy can undergo a successful repeat colonoscopy at a tertiary care centre with instruments that are readily available to most gastroenterologists. Other modalities for evaluation of the colon should be deferred until a second attempt is made at an expert centre.

CT colonography (CTC) is a robust and reliable imaging test of the colon. Accuracy for the detection of colorectal cancer (CRC) is as high as conventional colonoscopy (CC). Identification of polyp is size dependent, with large lesions (≥10mm) accurately detected and small lesions (6-9mm) identified with moderate to good sensitivity. Recent studies show good sensitivity for the identification of nonpolypoid (flat) lesions as well. Current CTC indications include the evaluation of patients who had undergone a previous incomplete CC or those who are unfit for CC (elderly and frail individuals, patients with underlying severe clinical conditions, or with contraindication to sedation). CTC can also be efficiently used in the assessment of diverticular disease (excluding patients with acute diverticulitis, where the exam should be postponed), before laparoscopic surgery for CRC (to have an accurate localization of the lesion), in the evaluation of colonic involvement in the case of deep pelvic endometriosis (replacing barium enema). CTC is also a safe procedure in patients with colostomy. For CRC screening, CTC should be considered an opportunistic screening test (not available for population, or mass screening) to be offered to asymptomatic average-risk individuals, of both genders, starting at age 50. The use in individuals with positive family history should be discussed with the patient first. Absolute contraindication is to propose CTC for surveillance of genetic syndromes and chronic inflammatory bowel diseases (in particular, ulcerative colitis). The use of CTC in the follow-up after surgery for CRC is achieving interesting evidences despite the fact that literature data are still relatively weak in terms of numerosity of the studied populations. In patients who underwent previous polypectomy CTC cannot be recommended as first test because debate is still open. It is desirable that in the future CTC would be the first-line and only diagnostic test for colonic diseases, leaving to CC only a therapeutic role.

Performing a complete colonoscopy to the cecum is important for ruling out malignancy and other lesions, but failure rates are significant with a standard colonoscope. A previous study using a push enteroscope for failed colonoscopies had a completion rate of 68.7%.

To improve the cecal intubation rate by using a newer version of a push enteroscope.

Retrospective study at first, then a prospective study.

Single-center veterans health care system.

A total of 47 patients in whom the cecum was not reached with a regular adult colonoscope between January 2007 and December 2010 were included. Those with poor bowel preparation were excluded.

Repeat colonoscopy using a new version of a push enteroscope.

The rate of cecal intubation and additional pathological findings.

The cecum or terminal ileum was reached in 45 patients (96%). Additional significant pathological findings in the previously unexamined colon were seen in 18 patients (38%).

Small sample size, lack of comparison with other endoscopes.

Colonoscopy with a push enteroscope could be advanced to either the terminal ileum or cecum in 96% of patients, which is one of the highest known completion rates in patients in whom colonoscopy failed. Clinical management changed in all patients with additional findings.

In 2008, CT colonography was approved by the American Cancer Society as a technique for screening for colorectal cancer. This approval should be considered an important step in the recognition of the technique, which although still relatively new is already changing some diagnostic algorithms. This update about CT colonography reports the quality parameters necessary for a CT colonographic study to be diagnostic and reviews the technical innovations and colonic preparation for the study. We provide a brief review of the signs and close with a discussion of the current indications for and controversies about the technique.

Elucidating the molecular mechanism underlying the development of adenoma, the major precursor lesion of colorectal cancer (CRC), would provide a basis for early detection, prevention as well as treatment of CRC. Using the highly sensitive 2-D DIGE method coupled with MS, we identified 24 differentially expressed proteins in adenoma tissues compared with matched normal colonic mucosa and CRC tissues. Fifteen proteins were downregulated and three proteins were upregulated in adenoma tissues when compared with individual-matched normal colonic mucosa. Five proteins were downregulated, while one protein was upregulated in adenoma tissues when compared with matched CRC tissues. A protein, β-tropomyosin (TM-β), recently suggested to be a biomarker of esophageal squamous carcinoma, was downregulated in both adenoma and CRC tissues. Additionally, the reduction in the level of TM-β in adenoma and CRC tissues was further validated by Western blotting (p<0.05) and RT-PCR (p<0.001). Our findings suggest that downregulation of TM-β is involved in the early development of CRC and that differentially expressed proteins might serve as potential biomarkers for detection of CRC.

The implementation of bowel cancer screening in the UK requires the maintenance of high standards in colonoscopy. Part of this quality control requires the reliable documentation of complete colonoscopy that can be externally audited and assessed. It has been suggested that terminal ileal biopsy is the only definitive and reliable method of confirming caecal intubation, but it is not cost-effective and may now be contraindicated because of potential prion infection.

To determine how reliable routine terminal ileal images were as an independent predictor of complete colonoscopy and whether their interpretation was aided with water insufflation or indigo-carmine dye-spraying. Method Forty-nine histologically confirmed terminal ileal images were obtained from a single endoscopist's database; 19 were conventional white-light images, 15 were taken with water insufflation and 15 were taken using chromoscopy enhancement. The images were transferred onto CD-ROM and sent as a questionnaire to 42 colonoscopists who were asked to identify the images as terminal ileum or not.

Twenty questionnaires were returned resulting in a total of 980 responses. Overall, the accuracy of positive identification was 53.4%. Water insufflation and chromoscopy improved the accuracy to 68.3% and 63% respectively. Experience of (> 1000 colonoscopies) did not increase overall accuracy. Less experienced endoscopists had an increased accuracy rate with dye-spraying (76.7%vs 59.3%, P < 0.05) but experienced endoscopists had an increased accuracy rate with water insufflation (67.4%vs 63.3%, P > .05).

Currently, terminal ileal imaging is not a reliable mode of documenting complete colonoscopy. Using water insufflation or dye-spraying coupled with modifications in image acquisition technique may improve its reliability but these methods require further investigation before they can replace the use of caecal landmarks as completion parameters.

The role of double-contrast barium enema examination (DCBE) in screening for colorectal carcinoma has evolved considerably in recent years. This review will discuss the current indications for DCBE and contrast fluoroscopy of the colon and the anticipated future role of these studies.

To retrospectively evaluate the positive predictive value (PPV) of computed tomographic (CT) colonography performed in patients who were referred for further examination after incomplete colonoscopy.

This HIPAA-compliant retrospective study was approved by the institutional review board; informed consent was waived. We identified 546 consecutive patients (mean age, 64.1 years; 401 [73.4%] women) who underwent CT colonography after incomplete colonoscopy between November 1999 and December 2002. A retrospective chart review was performed if CT colonography depicted endoscopically nonvisualized lesions 6 mm or greater in diameter. Repeat colonoscopy rate, endoluminal findings, and PPV of CT colonography were determined. Subsequent colonoscopic findings were used as the reference standard.

In 72 (13.2%) patients, CT colonography depicted 88 endoscopically nonvisualized lesions 6 mm or greater. Of 11 patients reported to have 12 masses (> or =20 mm), at subsequent colonoscopy, one patient had no mass. Eighteen patients had 23 large (10-19-mm) polyps that they were suspected of having, and 47 patients had 53 medium (6-9-mm) polyps that they were suspected of having. At a median follow-up of 31 months (range, 6-42 months), 45 (63%) of 72 patients underwent follow-up colonoscopy because of their CT colonographic findings. Rates of repeat colonoscopy for masses, large polyps, and medium polyps were 100%, 94%, and 45%, respectively. Per-patient and per-lesion PPVs of CT colonography for masses, large polyps, and medium polyps were 90.9% and 91.7%, 64.7% and 70%, and 33.3% and 30.4%, respectively.

CT colonography has the potential to become an accepted technique for evaluation of the nonvisualized part of the colon after incomplete colonoscopy, and it can increase the diagnostic yield of masses and clinically important polyps in this part of the colon.

Screening of asymptomatic average-risk patients for presence of colon cancer and early detection in precursor stages is of great interest to general population. Comprehensive evaluation of symptomatic or high-risk patients represents another important clinical focus. Available techniques for total colon imaging, rectal cancer staging and the role of positron emission tomography are discussed.

Over the past decade, computed tomographic (CT) colonography (also known as virtual colonoscopy) has been used to investigate the colon for colorectal neoplasia. Numerous clinical and technical advances have allowed CT colonography to advance slowly from a research tool to a viable option for colorectal cancer screening. However, substantial controversy remains among radiologists, gastroenterologists, and other clinicians with regard to the current role of CT colonography in clinical practice. On the one hand, all agree there is much excitement about a noninvasive imaging examination that can reliably depict clinically important colorectal lesions. However, this is tempered by results from several recent studies that show the sensitivity of CT colonography may not be as great when performed and the images interpreted by radiologists without expertise and training. The potential to miss important lesions exists; moreover, if polyps cannot be differentiated from folds and residual fecal matter, unnecessary colonoscopy will be performed. In this review, current issues will be discussed regarding colon cancer and the established and reimbursed strategies to screen for it and the past, current, and potential future role of CT colonography.

Among the major innovations in radiology of the gastrointestinal (GI) system are the replacement of classic invasive diagnostic methods with noninvasive ones and the improvement in lesion characterization and staging of pancreatobiliary malignancies. Developments in imaging technology have led to many improvements in the field of diagnostic GI radiology. With its fast and thin-section scanning abilities, multidetector-row CT (MDCT) strengthens the place of CT as the most efficient tool to diagnose, characterize, and preoperatively stage pancreatic neoplasms. MR cholangiopancreatography has widely replaced endoscopic retrograde cholangiopancreatography in the diagnosis and staging of pancreatobiliary malignancies. MR imaging, using phased-array or endorectal coils, demonstrates local tumor invasion accurately in rectal cancers and thus allows an improved surgical planning. Virtual colonoscopy with MDCTs is an efficient screening method for colon cancer, and MDCT enterography is becoming the standard imaging technique for many small bowel disorders. The continuing developments in CT and MR technology will most probably further improve the accuracy of these and other imaging applications in the near future.

Since its introduction in the late 1960s, the technology of colonoscopy has developed rapidly, and the competence of the endoscopists has increased. Still, a complete colonoscopy is not always possible to perform.

To assess, in a population-based setting, which patient factors influence the success rate.

All colonoscopy records during 1979-1995 in one Swedish county (population 258,000) were retrieved. Information was obtained about each patient's sex and age, date of examination, the endoscopist and indications for colonoscopy, findings, type of colonoscopy and reasons for an incomplete colonoscopy. Results were assessed by univariate and multivariate analyses.

Of 5145 colonoscopies, 4153 (81%) were complete. Completion rates were influenced by (odds ratio for completion [95% confidence intervals]): sex, male versus female (2.00 [1.39-2.86]); age, youngest quartile versus oldest quartile (1.49 [1.04-2.13]); indication for colonoscopy, previous colonic surgery or long-standing colitis versus other indications (2.08 [1.23-3.45]); and diverticulosis, presence versus no presence (0.79 [0.62-0.99]). The time period (proxy variable for the development of endoscopes) had no impact on completion rates.

The completion rate was lower than that has been reported from previous hospital-based studies. Lower completion rates were found in women, older patients and in patients with diverticulosis. Higher completion rates were noted in patients with previous colonic surgery and long-standing colitis. The completion rates were not influenced by the development of the endoscopes.

Conventional colonoscopy (CC) requires an experienced operator to avoid technical or interpretative errors, and an endoscopic error rate of 14% for tumor localization has been reported. We evaluated the impact of computed tomographic colonography (CTC) on surgical treatment strategy in patients with CC reported as having colorectal neoplasm.

Fifty-three patients testing positive for colorectal neoplasm on CC underwent CTC: 32 patients had CC in our hospital (group A) and 21 had CC in area hospitals (group B). All CTC procedures were performed with a multidetector CT system. The results of CTC and CC were compared with that of surgery. The preoperative surgical planning evaluated on the basis of CC and CTC was compared with the actual surgical approach, and the percentage of patients in whom CTC modified the treatment strategy suggested by CC was calculated.

CTC changed the treatment strategy in four of 53 patients (7.5%) in whom CC showed technical or interpretative errors. Group analysis showed that CTC did not influence the surgical management in any patient in group A but did affect treatment strategy in four of 21 patients (19%) in group B. The effect of CTC on treatment strategy between groups was statistically significant (p < 0.05). CTC identified five adenomas and three adenocarcinomas localized proximally to an impassable stenosis.

CTC can be used to reevaluate the findings of a positive CC and can indicate a more correct therapeutic approach in patients with colorectal neoplasms who are candidates for surgery.

To compare thin-section multi-detector row computed tomographic (CT) colonography with conventional colonoscopy in the evaluation of colorectal polyps and cancer in asymptomatic average-risk patients.

Sixty-eight asymptomatic men (age > 50 years) scheduled to undergo screening colonoscopy were enrolled in this study. CT colonography was followed by conventional colonoscopy, performed on the same day. Supine and prone CT colonography were performed after colonic insufflation with room air. A gastroenterologist measured all polyps, which were categorized as 1-5, 6-9, or over 10 mm. Biopsy and histologic evaluation were performed of all polyps. CT colonography and colonoscopy results were compared for location, size, and morphology of detected lesions. Point estimates and 95% CIs were provided for specificity and sensitivity of CT by using results at conventional colonoscopy as the reference standard.

At colonoscopy, 98 polyps were identified in 39 patients; 21 (21.4%) of 98 were detected at CT colonography. Sensitivity was 11.5% (nine of 78) for polyps 1-5 mm, 52.9% (nine of 17) for polyps 6-9 mm, and 100% (three of three) for polyps over 10 mm. Results at colonoscopy were normal in 29 (42.6%) of 68 patients; at CT colonography, results were correctly identified as normal in 26 of these 29 patients. In one of these patients, a lesion larger than 10 mm was detected at CT colonography. The per-patient specificity of CT was 89.7% (26 of 29; 95% CI: 72.7%, 97.8%). The mean time for CT image interpretation was 9 minutes.

In patients at average risk for colorectal cancer, CT colonography is a sensitive and specific screening test for detecting polyps 10 mm or larger; the sensitivity for detecting smaller polyps is decreased. Examination findings can be interpreted in a clinically feasible amount of time.

In the last decade, computed tomographic (CT) and magnetic resonance (MR) colonography, two new cross-sectional techniques for imaging of the colon, emerged. Both techniques show promising initial results in the detection of polyps equal to or greater than 1 cm in diameter in symptomatic patients. Imaging protocols are still mostly under development and prone to change. Both CT and MR colonography generate a large number of source images, which have to be read carefully for filling defects and, if intravenous contrast material is used, enhancing lesions. An important postprocessing technique is multiplanar reformatting, which allows the viewer to see potential lesions in an orientation other than that of the source images. Virtual endoscopy, a volume rendering technique that generates images from within the colon lumen, is used for problem solving. CT and MR colonography have potential advantages over colonoscopy and double-contrast barium enema examination: multiplanar capabilities, detection of enhancing lesions that make the distinction between fecal residue and true lesion possible, and ante- and retrograde virtual colonoscopy. Currently, a number of studies suggest that patients have a preference for CT colonography over colonoscopy. Patients consider bowel cleansing the most uncomfortable part of any colon examination; hence, from the acceptance point of view, fecal tagging techniques are promising. Before CT and MR colonography can be implemented in daily practice, they must show approximately the same accuracy as colonoscopy for polyp detection in both symptomatic and screening patients.

This study used a low lesion prevalence population reflective of the screening setting to estimate the sensitivity and specificity of computerized tomographic (CT) colonography for detection of colorectal polyps.

This prospective, blinded study comprised 703 asymptomatic persons at higher-than-average risk for colorectal cancer who underwent CT colonography followed by same-day colonoscopy. Two of 3 experienced readers interpreted each CT colonography examination.

Overall lesion prevalence for adenomas >/=1 cm in diameter was 5%. Seventy percent of all lesions were proximal to the descending colon. With colonoscopy serving as the gold standard, CT colonography detected 34%, 32%, 73%, and 63% of the 59 polyps >/=1 cm for readers 1, 2, 3, and double-reading, respectively; and 35%, 29%, 57%, and 54% of the 94 polyps 5-9 mm for readers 1, 2, 3, and double-reading, respectively. Specificity for CT colonography ranged from 95% to 98% and 86% to 95% for >1 cm and 5-9-mm polyps, respectively. Interobserver variability was high for CT colonography with kappa statistic values ranging from -0.67 to 0.89.

In a low prevalence setting, polyp detection rates at CT colonography are well below those at colonoscopy. These rates are less than previous reports based largely on high lesion prevalence cohorts. High interobserver variability warrants further investigation but may be due to the low prevalence of polyps in this cohort and the high impact on total sensitivity of each missed polyp. Specificity, based on large numbers, is high and exhibits excellent agreement among observers.

Virtual endoscopy is a new-generation technique which combines the features of endoscopic viewing and cross-sectional volumetric imaging. In the evaluation of gastrointestinal cancers, virtual endoscopy has been most commonly used in colorectal carcinomas and to a much lesser extent in gastric carcinomas. In this review, the current status of virtual colonoscopy was reviewed together with a brief discussion of virtual gastroscopy.

Colorectal carcinomas are the most common gastrointestinal tract tumors. 50-60% of the colorectal carcinomas originate in rectum and sigmoid colon. The new developments in imaging modalities have brought improvements in therapeutic aspects. The survival rates in these patients depend on the tumor penetration and the presence of regional lymph node or distant metastasis. The recurrence rates have decreased with the new operation techniques and preoperative radiotherapy, thus increasing the importance of accurate tumor staging. Double contrast barium enema studies enable the diagnosis while staging and follow-up is best done by topographic imaging techniques.

To determine the diagnostic yield of barium enema examination for neoplastic lesions larger than 1 cm in diameter in the nonvisualized portion of the colon after incomplete colonoscopy.

A review of computerized gastroenterology and radiology databases identified 355 patients who underwent incomplete colonoscopy; 158 (44.5%) underwent subsequent barium enema examination (125 double-contrast and 33 single-contrast barium enema examinations). The radiographic reports were reviewed and compared with the endoscopic reports by one author to identify neoplastic lesions larger than 1 cm in the nonvisualized colon after incomplete colonoscopy. Six such lesions were found. In all six cases, the images from the barium enema examinations were reviewed together by two authors to determine the size, location, and morphologic features (polypoid, ulcerated, or annular) of the lesions. Medical, endoscopic, and surgical records were subsequently reviewed by one author to determine whether these represented true- or false-positive radiographic findings.

Barium enema examination depicted six possible lesions in the nonvisualized colon after incomplete colonoscopy; five were found to be true-positive radiographic findings, and one was found to be a false-positive finding. The five true-positive findings included two annular lesions (both adenocarcinomas) and three polypoid lesions (all tubulovillous adenomas, with high-grade dysplasia in one). Thus, neoplastic lesions larger than 1 cm were found on barium enema images in the nonvisualized colon in five (3.2%) of 158 patients after incomplete colonoscopy.

Barium enema examination had a diagnostic yield of 3.2% for neoplastic lesions larger than 1 cm in the nonvisualized colon after incomplete colonoscopy.

Computerized tomographic colonography (CT colonography) is a new, non-invasive technique that has been developed over the last few years; it looks at the large bowel in detail. In this chapter we look at how the examination is performed and we consider how the images are displayed. We describe the normal features of the colon, as seen using this technique, as well as the features of common pathological conditions. We will discuss screening for colorectal cancer and the performance of CT colonography; we compare the latter with other procedures currently employed in the screening and diagnosis of colorectal pathology. We consider the difficulties in interpreting these CT colonographic images and look at ways to overcome such difficulties. Finally we discuss future developments of this exciting, new technique.

CT colonography is an evolving noninvasive imaging technique that allows detection of colorectal polyps and cancers. When assessing the clinical results of this test, several points need to be emphasized. First, as computed tomography (CT) technology improves, so will clinical results. Therefore, earlier results reporting the accuracy of CT colonography may not be applicable to the current state of the art. Second, as clinical experience has grown, an understanding of the limitations and pitfalls of the technique has increased. A learning curve is involved and, with increased experience, results should improve. This article will focus on the evolving clinical results of CT colonography.

It is generally accepted that clinicians performing colonoscopy should reach the cecum in at least 90 percent of examinations. However, little attention has been paid to whether the endoscopist correctly estimates the amount of colon actually seen.

During colonoscopy, endoscopists were asked to state how far they had reached. This was compared with the amount of colon actually seen, as assessed by a novel electromagnetic imaging device that recorded a three-dimensional position of the scope within a magnetic field pervading the patient's abdomen. If electromagnetic imaging showed that the cecum had not been reached, the endoscopist was asked to use the electromagnetic imaging system to determine whether it helped advance the colonoscope further.

In 119 patients undergoing colonoscopy, clinical assessment of position reached was correct in only 92 (77.3 percent). When the endoscopists stated that cecal landmarks had been seen (n = 85), the scope was distal to the cecum in seven cases (8.2 percent). When cecal landmarks had not been seen (n = 34), the endoscopist's assessment of the position of the scope was accurate in only 14 (41.2 percent). The use of electromagnetic imaging in this latter group assisted passage to the cecum in 26 cases (76.5 percent).

Despite assumed visualization of the cecum, inadequate colonoscopy highlights the potential for missing significant pathology in the right colon.

The double-contrast barium enema examination has been recognized as an option for colorectal cancer screening in Americans with average risk who are greater than 50 years of age. The purpose of this article is to review the principles for diagnosing colorectal neoplasms on double-contrast images and the spectrum of findings associated with these lesions. Colonic polyps can be sessile or pedunculated; their appearance depends on whether they are located on the dependent or nondependent wall of the bowel. Villous tumors may be flat, lobulated lesions, also known as "carpet" lesions, that are characterized by a finely nodular or reticular surface pattern, without a discrete mass. Colonic carcinomas may manifest as plaquelike, polypoid, semiannular ("saddle") or annular lesions. Colonic neoplasms sometimes are more difficult to detect in the region of the ileocecal valve or the distal rectum or in patients with severe diverticulosis. Careful double-contrast technique and meticulous scrutiny of the images therefore are required to optimize detection of these lesions.

Our aim was to describe, in a population-based setting, the use of colonoscopy over time with special emphasis on indications, the competence of the endoscopists, and the frequency of total colonoscopies and to compare the number of colonoscopies with that of barium enemas.

All colonoscopy records during 1979-95 in a Swedish county (population, 258,000) were retrieved. Information was collected about the patients' demographics, the endoscopists, indications, findings, and type of colonoscopy.

A total of 6066 colonoscopies were performed in 4304 patients by 62 endoscopists. Of these, 562 were not intended to be complete; of the other 5504 colonoscopies, 4153 were complete (75%). Of the patients 77% had undergone colonoscopy once, 14% twice, and 9% three times or more. Among the endoscopists 73% never performed more than 50 colonoscopies, and 5% did more than 700 colonoscopies. Bleeding as an indication increased from 10% to 31%; polyps decreased from 30% to 10%, and unclear X-ray findings decreased from 28% to 4%. Diarrhoea and abdominal pain, both 0% in 1979, increased to 6% and 5%, respectively. Surveillance (cancer, polyps, colitis) was fairly stable, at 25%. Both the rate of complete colonoscopies and the proportion of colonoscopies done by experienced endoscopists increased with time. The annual number of barium enemas was relatively constant until 1992 but then decreased.

The increased use of colonoscopy has resulted in a decrease in barium enemas. The competence of the endoscopists increased, resulting in a higher rate of complete colonoscopies.

After patients have undergone colonoscopic polypectomy, it is uncertain whether colonoscopic examination or a barium enema is the better method of surveillance.

As part of the National Polyp Study, we offered colonoscopic examination and double-contrast barium enema for surveillance to patients with newly diagnosed adenomatous polyps. Although barium enema was performed first, the endoscopist did not know the results.

A total of 973 patients underwent one or more colonoscopic examinations for surveillance. In the case of 580 of these patients, we performed 862 paired colonoscopic examinations and barium-enema examinations that met the requirements of the protocol. The findings on barium enema were positive in 222 (26 percent) of the paired examinations, including 139 of the 392 colonoscopic examinations in which one or more polyps were detected (rate of detection, 35 percent; 95 percent confidence interval, 31 to 40 percent). The proportion of examinations in which adenomatous polyps were detected by barium enema colonoscopy was significantly related to the size of the adenomas (P=0.009); the rate was 32 percent for colonoscopic examinations in which the largest adenomas detected were 0.5 cm or less, 53 percent for those in which the largest adenomas detected were 0.6 to 1.0 cm, and 48 percent for those in which the largest adenomas detected exceeded 1.0 cm. Among the 139 paired examinations with positive results on barium enema and negative results on colonoscopic examination in the same location, 19 additional polyps, 12 of which were adenomas, were detected on colonoscopic reexamination.

In patients who have undergone colonoscopic polypectomy, colonoscopic examination is a more effective method of surveillance than double-contrast barium enema.

We compared the findings of time-efficient CT colonography with complete two-dimensional (2D) and three-dimensional (3D) CT colonography and conventional colonoscopy in detecting colorectal polyps.

Forty-two patients undergoing colonoscopy screening were examined with CT colonography before endoscopy. Data were examined following one of two methods. In method 1, axial 2D data sets were examined in a cine mode. If findings were suggestive of abnormality, focal areas were examined with 3D CT colonography. In method 2, data sets were examined exactly as in method 1, and subsequent to that review, data sets were examined with simultaneous 3D "fly-through" CT colonography (surface-rendered images) and multiplanar reformatted images. The time required to examine CT colonography using each technique was recorded and abnormal findings were documented. Results of methods 1 and 2 were compared with findings on colonoscopy.

Colonoscopy detected 16 polyps in 13 patients (polyp size, 2-10 mm). Ten polyps measured 5 mm or less, five measured between 6 and 9 mm, and one measured 10 mm or more. Using method 1, two of 10 polyps measuring less than 5 mm, three of five polyps measuring between 6 and 9 mm, and one polyp measuring 10 mm were detected. We noted no false-positive polyps. Average evaluation time was 16 min. With method 2, the same polyps were seen as with method 1. No additional polyps were detected, and the average evaluation time was 40 min.

Axial 2D CT colonography can be performed quickly and is comparable with complete 2D and 3D CT colonography in detecting colorectal polyps.

To establish whether biopsy of the ileocaecal valve from the caecum provides an alternative to the more technically demanding procedure of terminal ileal intubation and biopsy to document completion of colonoscopy.

Fifty-three patients underwent colonoscopy at which the terminal ileum was intubated and biopsied and, after withdrawal of the endoscope tip into the caecum, the ileocaecal valve was then biopsied. To replicate the situation in which the ileum is not intubated, another group of 30 patients had ileocaecal valve biopsies taken from the caecum before ileal intubation was attempted.

All of the terminal ileal biopsies obtained before ileocaecal valve biopsy showed small bowel mucosa, as did 51 (96%) of the ileocaecal valve specimens from this group. When ileocaecal valve biopsy was obtained first, 16 (53%) specimens contained small bowel mucosa.

Ileocaecal valve biopsies were significantly more likely to yield small bowel mucosa if taken after ileal intubation (P < 0.001, Fisher's exact test). Nevertheless, about half of ileocaecal valve biopsies taken without ileal intubation contained small bowel mucosa, providing evidence of complete colonoscopy in these cases. Terminal ileal intubation and biopsy, however, remains the only reliable way to document complete colonoscopy.

While colonoscopy has become established as more accurate than double contrast barium enema for detecting colonic polyps and cancers, as well as offering the opportunity for therapy, there are occasional instances where colonoscopy is misleading. The present study is to determine what problems occur, with a view to finding a solution.

The records of the Colorectal Project at the Princess Alexandra Hospital indicate retrospectively that 346 patients have been correctly diagnosed with cancer of the colon and rectum by colonoscopy in the 5 years up to October 1996. During the same time eight patients (2.3%) were recorded at the same hospital as being misdiagnosed by colonoscopy, the lesion being either missed completely or misplaced.

In five of these patients there was failure to recognize that the whole colon had not been examined endoscopically, thereby missing a more proximal lesion. In two patients the lesion was missed although the entire colon was examined. In one patient the lesion was discovered but inaccurately sited. Six of these mistakes would have been obviated by the routine use of fluoroscopy to confirm the totality of the colonoscopy and to site any lesions found. The other two cases occurred because of failure to remember that colonic examination during withdrawal should be performed meticulously back as far as the anal canal. Failure to diagnose a colon cancer on the initial colonoscopy led to an average delay of 6 months for definitive care.

It is recommended that fluoroscopy be used routinely during colonoscopy to site accurately any lesions found, and to confirm the completeness of insertion if reliable landmarks, including terminal ileum, are not clearly identified.