Virtual colonography: Identification and differentiation of colorectal lesions using multi-detector computed tomography

Objective. Early detection of precancerous or malignant lesions may be decisive for prognosis of patients with colorectal cancer. In this prospective feasibility study, multi-detector spiral computed tomography (CT) colonography was compared with conventional colonoscopy for the detection of colorectal polyps. Material and methods. Seventy-eight patients underwent CT colonography (standard colonoscopy preparation, distension with room air, prone and supine position) immediately before colonoscopy. Sixty-five (83%) were asymptomatic screening subjects, while the rest had symptoms suggestive of colorectal disease. Presence, location, and size of lesions were prospectively assessed. Sensitivity, specificity, and positive and negative predictive values of CT colonography were calculated using conventional colonoscopy as the reference standard. Results. Conventional colonoscopy was normal in 52 patients. In 26 patients a total of 49 polyps and 3 carcinomas were identified. All three carcinomas and 39 polyps (80%) were identified by CT colonography. Seven of 7 polyps ≥10 mm (100%), 13 of 16 polyps of 6 to 9 mm (81%), and 19 of 26 polyps ≤5 mm (73%) in diameter were identified. Fourteen false-positive findings (10 of which were ≤5 mm in diameter) were related to 8 patients (specificity at the patient level was 86%). In 10 patients, a total of 10 polyps were missed by CT colonography, 7 of which were ≤5 mm in diameter. Conclusions. In this feasibility study, multi-detector spiral CT colonography allows accurate detection of polyps>5 mm in diameter, but at the expense of low specificity in the small size range.     

Computed tomographic colonography compared with colonoscopy in patients at increased risk for colorectal cancer

BACKGROUND & AIMS: To date, computed tomographic (CT) colonography has been compared with an imperfect test, colonoscopy, and has been mainly assessed in patients with positive screening test results or symptoms. Therefore, the available data may not apply to screening of patients with a personal or family history of colorectal polyps or cancer (increased risk). We prospectively investigated the ability of CT colonography to identify individuals with large (>or=10 mm) colorectal polyps in consecutive patients at increased risk for colorectal cancer. METHODS: A total of 249 consecutive patients at increased risk for colorectal cancer underwent CT colonography before colonoscopy. Two reviewers interpreted CT colonography examinations independently. Sensitivity, specificity, and predictive values were determined after meticulous matching of CT colonography with colonoscopy. Unexplained large false-positive findings were verified with a second-look colonoscopy. RESULTS: In total, 31 patients (12%) had 48 large polyps at colonoscopy. This included 8 patients with 8 large polyps that were overlooked initially and detected at the second-look colonoscopy. In 6 of 8 patients, the missed polyp was the only large lesion. With CT colonography, 84% of patients (26/31) with large polyp(s) were identified, paired for a specificity of 92% (200-201/218). Positive and negative predictive values were 59%-60% (26/43-44) and 98% (200-201/205-206), respectively. CT colonography detected 75%-77% (36-37/48) of large polyps, with 9 of the missed lesions being flat. CONCLUSIONS: CT colonography and colonoscopy have a similar ability to identify individuals with large polyps in patients at increased risk for colorectal cancer. The large proportion of missed flat lesions warrants further study.     

Prospective blinded evaluation of computed tomographic colonography for screen detection of colorectal polyps

BACKGROUND & AIMS: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Mucosal Spreading Depressed Type Colorectal Tumors: A Report of Two Cases

Abstract: Superficial depressed type colorectal carcinomas usually show invasion into the submucosa while the tumor is small, measuring less than 10 mm in diameter. We experienced two rare cases of superficial depressed type colorectal tumors of more than 15 mm in diameter which only displayed intramucosal spread. These two lesions showed a clearly depressed appearance on colonoscopy and in the resected specimens, which were different from creeping tumors. One of the lesions was histologically diagnosed as being well differentiated adenocarcinoma without submucosal invasion, and the other was an adenoma with severe atypia. Both lesions had no Ki-ras point mutation and this result was consistent with recent genetic studies on depressed type colorectal tumor. Based on these colonoscopic findings, a simple change in the quantity of air inside the lumen may effectively distinguish a depressed type tumor larger than 15 mm, which is limited to the mucosa, from one with submucosal invasion. Thus bowel resection can be avoided in such cases.     

Korean experience of superficial depressed‐type early colorectal cancer

Background: Unlike the adenoma–carcinoma sequence theory, the de novo carcinoma theory has been highlighted recently because of the emergence of superficial depressed‐type early colorectal cancers. In addition, some flat‐elevated or sessile‐type early colorectal cancers have been identified as originating from superficial depressed‐type early colorectal cancers. Thus, studies of superficial depressed‐type early colorectal cancers may provide an opportunity to clarify the morphogenesis of colorectal cancers in the foreseeable future. Methods: The authors studied 231 cases of early colorectal cancer from 1997 to 2000. Among them, 17 cases (7.4%) were superficial depressed‐type. According to Kudo's classification, the 17 lesions were classified as three types based on their growth patterns: IIc, IIa + IIc, and Is + IIc. They were also classified as sm‐s (sm₁) and sm‐m (sm_2–3) cancers based on the depth of submucosal invasion according to Kudo's classification. They were analyzed with emphasis on size, depth of submucosal invasion and treatment. Results: Type IIc lesions were 11 mm in diameter on average; types IIa + IIc and Is + IIc had diameters of 15 mm and 11 mm on average, respectively. Sm‐m cancers' diameters were all larger than 10 mm. Fifty‐seven percent (57%) of type IIc cancers were submucosally invasive, while 90% of type IIa + IIc and type Is + IIc cancers together were submucosally invasive. The overall surgical resection rate was 41.2%, and surgical resection was performed in 80% of the sm‐m cases. Conclusion: Recognition of superficial depressed‐type early colorectal cancers, especially type IIa + IIc and type Is + IIc cancers, is important because their biological behavior will most likely be different from that of the usual protruding early cancers. Accordingly, the treatment modality should be selected prudentially, and early detection is imperative in order for their sizes to be less than 10 mm.     

Clinicopathological features of nonpolypoid colorectal tumors as viewed from the patients' background

Background This study was performed to characterize the clinicopathological features of colorectal tumors with flat-, depressed-, or protruded-type morphology (hereafter referred to simply as flat, depressed, or protruded lesions). Methods There are two major types of colorectal tumor: polypoid (protruded) and nonpolypoid (flat and depressed). A total of 130 lesions from 130 patients with colorectal submucosal invasive cancer were classified into three groups according to their macromorphology seen during endoscopy: flat (laterally spreading) and depressed nonpolypoid tumors and protruded polypoid tumors. The following factors in the patients' background were evaluated: indication for colonoscopy, age, and family history of colorectal cancer in first-degree relatives (i.e., parents, siblings, children). We also compared the following characteristics of the tumors: size, location, depth of submucosal invasion, vascular invasion, and frequency of synchronous and metachronous tumor lesions. Results The incidence of abnormal findings on follow-up studies after polypectomy as an indication for colonoscopy was significantly higher among patients with flat lesions (4/24, 16.7%) and depressed lesions (3/22, 13.6%) than among those with protruded lesions (1/84, 1.2%) (P < 0.01, P < 0.01). Patients with flat lesions (65.8 ± 7.6 years old) were significantly older than those with protruded lesions (P < 0.05). The patients with flat tumors had a significantly higher rate of a family history of colorectal cancer (6/24, 25.0%) than patients with protruded or depressed lesions (P < 0.01, P < 0.05). The protruded lesions were significantly larger than the depressed lesions (size 13.3 ± 6.7 mm) (P < 0.05), and the flat lesions (24.1 ± 10.1 mm) were significantly larger than either the protruded or depressed lesions (P < 0.01, P < 0.01). Seventy-five percent (18/24) of the flat lesions were located in the right colon, and this proportion was significantly higher than that among the protruded or depressed lesions (P < 0.01, P < 0.01). The mean ± SD depth of submucosal invasion was 1218 ± 1034 μm in the flat lesions, 2392 ± 1869 μm in the depressed lesions, and 2761 ± 1929 μm in the protruded lesions, representing a significant difference (P < 0.05, P < 0.0001). Of the 24 patients with flat lesions, 9 (37.5%) showed vascular invasion; this proportion was significantly lower than that among patients with the depressed or protruded lesions (P < 0.01, P < 0.01). Patients with depressed lesions tended to have higher incidence of synchronous and metachronous malignant polyps than those with protruded or flat lesions. Conclusion It is important to examine the morphology of colorectal tumors when diagnosing them and planning the treatment strategy, including follow-up, after resection of nonpolypoid tumors. It is useful to know the patient's family history so nonpolypoid tumors can be accurately diagnosed.     

Role of virtual computed tomographic colonography in patients with colorectal cancers and obstructing colorectal lesions

PURPOSE: The aim of this study was to assess the ability of computed tomographic colonography to diagnose colorectal masses, stage colorectal cancers, image the proximal colon in obstructing colorectal lesions, and evaluate the anastomoses in patients with previous colorectal surgery. METHODS: We prospectively performed computed tomographic colonography examinations in 34 patients (20 males; mean age, 64.2; range, 19–91 years): 20 patients had colorectal masses (defined at endoscopy as intraluminal masses 2 cm or larger), 7 patients had benign obstructing colorectal strictures, and 7 patients had a prior colorectal resection. Final tumor staging was available in all 16 patients who had colorectal cancers and 15 patients were referred after incomplete colonoscopy. The ability of computed tomographic colonography to stage colorectal cancers, identify synchronous lesions in patients with colorectal masses, and image the proximal colon in patients with obstructing colorectal lesions was assessed. RESULTS: Computed tomographic colonography identified all colorectal masses, but overcalled two masses in patients who were either poorly distended or poorly prepared. Computed tomographic colonography correctly staged 13 of 16 colorectal cancers (81 percent) and detected 16 of 17 (93 percent) synchronous polyps. Computed tomographic colonography overstaged two Dukes Stage A cancers and understaged one Dukes Stage C cancer. A total of 97 percent (87/90) of all colonic segments were adequately visualized at computed tomographic colonography in patients with obstructing colorectal lesions compared with 60 percent (26/42) of segments at barium enema (P<0.01). Colonic anastomoses were visualized in all nine patients, but in one patient, computed tomographic colonography could not distinguish between local tumor recurrence and surgical changes. CONCLUSION: Computed tomographic colonography can accurately identify all colorectal masses but may overcall stool as masses in poorly distended or poorly prepared colons. Computed tomographic colonography has an overall staging accuracy of 81 percent for colorectal cancer and is superior to barium enema in visualizing colonic segments proximal to obstructing colorectal lesions.Read at The American Society of Colon and Rectal Surgeons' 100th Anniversary and Tripartite Meeting, Washington D.C., May 1 to 6, 1999.     

Prospective Study Comparing Multislice CT Colonography With Colonoscopy in the Detection of Colorectal Cancer and Polyps

PURPOSE: Multislice CT colonography is an alternative to colonoscopy. The purpose of this study was to compare multislice CT colonography with colonoscopy in the detection of colorectal polyps and cancers. METHODS: Between June 2000 and December 2001, 45 males and 35 females (median age, 68 (29–83) years) with symptoms of colorectal disease were studied prospectively. All patients underwent multislice CT colonography and colonoscopy, and the findings were compared. RESULTS: Colonoscopy was incomplete in 18 (22 percent) patients because of obstructing lesions or technical difficulty, and multislice CT colonography was unsuccessful in 4 (5 percent) because of fecal residue. Colonoscopy was normal in 26 patients and detected 29 colorectal cancers and 33 polyps in 35 patients, diverticulosis in 16 patients, and colitis in 3 patients. Multislice CT colonography identified 28 of 29 colorectal cancers with one false negative and one false positive (sensitivity, 97 percent; specificity, 98 percent; positive predictive value, 96 percent; negative predictive value, 98 percent). Multislice CT colonography identified all 12 polyps measuring 10 mm in diameter (sensitivity, 100 percent), 5 of 6 measuring 6 to 9 mm in diameter (sensitivity, 83 percent), 8 of 15 polyps 5 mm (sensitivity, 53 percent), and false-positive for 8 polyps. The overall sensitivity was 74 percent and specificity 96 percent. The positive predictive value for polyps was 88 percent, and the negative predictive value was 90 percent. Multislice CT colonography also detected 5 of 16 patients with diverticulosis (sensitivity, 31 percent; specificity, 98 percent) and colitis in 2 of 3 patients (sensitivity, 67 percent; specificity, 100 percent). In ten (13 percent) patients, extracolonic findings on multislice CT colonography altered management and included five patients with colorectal liver metastases. In 15 (19 percent) patients, there were incidental findings that did not demand further investigation. CONCLUSIONS: The results from this study indicate that the efficacy of multislice CT colonography in the detection of colorectal cancers and polyps 6 mm is similar to colonoscopy. Multislice CT colonography allows clinical staging of colorectal cancers, outlines the whole length of the colon in obstructing carcinoma when colonoscopy fails, and can identify extracolonic causes of abdominal symptoms.     

Virtual colonography: identification and differentiation of colorectal lesions using multi-detector computed tomography

OBJECTIVE: Early detection of precancerous or malignant lesions may be decisive for prognosis of patients with colorectal cancer. In this prospective feasibility study, multi-detector spiral computed tomography (CT) colonography was compared with conventional colonoscopy for the detection of colorectal polyps. MATERIAL AND METHODS: Seventy-eight patients underwent CT colonography (standard colonoscopy preparation, distension with room air, prone and supine position) immediately before colonoscopy. Sixty-five (83%) were asymptomatic screening subjects, while the rest had symptoms suggestive of colorectal disease. Presence, location, and size of lesions were prospectively assessed. Sensitivity, specificity, and positive and negative predictive values of CT colonography were calculated using conventional colonoscopy as the reference standard. RESULTS: Conventional colonoscopy was normal in 52 patients. In 26 patients a total of 49 polyps and 3 carcinomas were identified. All three carcinomas and 39 polyps (80%) were identified by CT colonography. Seven of 7 polyps > or = 10 mm (100%), 13 of 16 polyps of 6 to 9 mm (81%), and 19 of 26 polyps < or = 5 mm (73%) in diameter were identified. Fourteen false-positive findings (10 of which were < or = 5 mm in diameter) were related to 8 patients (specificity at the patient level was 86%). In 10 patients, a total of 10 polyps were missed by CT colonography, 7 of which were < or = 5 mm in diameter. CONCLUSIONS: In this feasibility study, multi-detector spiral CT colonography allows accurate detection of polyps > 5 mm in diameter, but at the expense of low specificity in the small size range.     

Flat and depressed colorectal tumours in a southern Swedish population: a prospective chromoendoscopic and histopathological study

BACKGROUND: Flat and depressed colorectal tumours are common in Japan but are very rare or non-existent in Western countries. AIMS: To study the occurrence of flat colorectal tumours in a southern Swedish population. METHODS: In this prospective study, 371 consecutive European patients were examined by high resolution video colonoscopy combined with chromoendoscopy. The nature of the lesions was determined by histopathological examination. RESULTS: A total of 973 tumours were found; 907 (93.2%) were protruding and 66 (6.8%) were flat or depressed. Of the flat/depressed tumours, five (7.7%) were early adenocarcinomas infiltrating the submucosa. Eleven carcinomas (1.2%) were found among protruding tumours. High grade dysplasia was observed in 18% (n=11) of flat/depressed adenomas in contrast with 7.3% (n=65) of protruding adenomas, and occurred in smaller flat/depressed tumours compared with protruding ones (mean diameter 8 mm v 23 mm, respectively). Furthermore, high grade dysplasia was significantly more common in flat elevated tumours with central depression or in depressed adenomas (35.7%; 5/14) than in flat elevated adenomas (12.8%; 6/47). CONCLUSION: Flat and depressed tumours exist in a Western population. Future studies should address whether or not chromoendoscopy with video colonoscopy is necessary in the search for flat colorectal neoplasms.     

Prospective comparison of contrast enhanced CT colonography and conventional colonoscopy for detection of colorectal neoplasms in a single institutional study using second-look colonoscopy with discrepant results

BACKGROUND: Colorectal cancer is the second leading cause of death from cancer in Western countries. Early detection by colorectal cancer screening can effectively cut its mortality rate. CT colonography represents a promising, minimally invasive alternative to conventional methods of colorectal carcinoma screening. AIMS: The purpose of this prospective single institutional study was to compare the abilities of routine clinical CT colonography and conventional colonoscopy to detect colorectal neoplasms using second-look colonoscopy to clarify discrepant results. PATIENTS AND METHODS: CT colonography was performed in 100 symptomatic patients using contrast enhanced multidetector CT followed by conventional colonoscopy on the same day. If results were discrepant, a second-look colonoscopy was performed after unblinding. CT colonographic findings were compared with those of conventional colonoscopy. RESULTS: Conventional colonoscopy found 122 colorectal neoplasms in 49 patients. The overall sensitivity of CT colonography at detecting patients with at least one polyp 6 mm or larger was 76% and its specificity was 88%. Its by-patient sensitivity for polyps 10 mm or larger was 95% and its specificity was 98%. By-polyp sensitivities were 71% for polyps 10 mm or larger, and 61% for polyps 6 mm or larger. A second-look colonoscopy was performed in 19 patients and two initial false-positive findings of CT colonography were reclassified as true-positive. For conventional colonoscopy, this produced a by-polyp sensitivity of 94% for detection of lesions 6 mm and larger. CONCLUSIONS: CT colonography had both a high by-patient sensitivity and specificity for detection of clinically important colorectal neoplasms 10 mm or larger. This suggests that CT colonography has the potential to become a valuable clinical screening method for colorectal neoplasms.     

Detectability of colorectal neoplastic lesions using a narrow‐band imaging system: A pilot study

Background and Aim: Flat and depressed colorectal neoplastic lesions can be difficult to identify using conventional colonoscopy techniques. Narrow‐band imaging (NBI) provides unique views especially of mucosal vascular network and helps in visualization of neoplasia by improving contrast. The aim of this study was to assess the feasibility of using NBI for colorectal neoplasia screening. Methods: Forty‐seven consecutive patients, who underwent high definition colonoscopy (HDC) screening examinations revealing neoplastic lesions, were enrolled in our prospective study. No biopsies or resections were performed during the initial HDC, but patients in whom lesions were detected underwent further colonoscopies using NBI, with the results of the first examination blinded from the colonoscopist. They then received appropriate treatment. We compared diagnostic detection rates of neoplastic lesions for HDC and NBI procedures using total number of all identified neoplastic lesions as reference standard. Results: Altogether, 153 lesions were detected and analyzed in 43 patients. Mean diagnostic extubation times were not significantly different (P = 0.18), but the total number of lesions detected by NBI was higher (134 vs 116; P = 0.02). Based on macroscopic type, flat lesions were identified more often by NBI (P = 0.04). As for lesion size, only flat lesions < 5 mm were detected more frequently (P = 0.046). Lesions in the right colon were identified more often by NBI (P = 0.02), but NBI missed two flat lesions ≥ 10 mm located there. Conclusions: Narrow band imaging colonoscopy may represent a significant improvement in the detection of flat and diminutive lesions, but a future multi‐center controlled trial should be conducted to fully evaluate efficacy for screening colonoscopies.     

Evaluation of contrast-enhanced computed tomographic colonography in detection of local recurrent colorectal cancer

AIM:To evaluate the diagnostic accuracy,sensitivity,specificity of contrast-enhanced computed tomographiccolonography in detecting local recurrence of colorectalcancer.METHODS:From January 2000 to December 2004,434 patients after potentially curative resection for in-vasive colorectal cancer were followed up for a periodranging from 20 to 55 mo.Eighty of the four hundredand thirty-four patients showing strong clinical evidencefor recurring colorectal cancer during the last follow-up were enrolled in this study.Each patient underwentcontrast-enhanced computed tomographic colonographyand colonoscopy on the same day.Any lesions,biopsies,identified during the colonoscopic examination,imme-diate complications and the duration of the procedurewere recorded.The results of contrast-enhanced com-puted tomographic colonography were evaluated bycomparing to those of colonoscopy,surgical finding,andclinical follow-up.RESULTS:Contrast-enhanced computed tomographiccolonography had a sensitivity of 100%,a specificity of83% and an overall accuracy of 94% in detecting localrecurrent colorectal cancer.CONCLUSION:Conventional colonoscopy and contrast-enhanced tomographic colonography can complementeach other in detecting local recurrence of colorectalcancer.     

CT Colonography Can Be an Adjunct to Optical Colonoscopy in CRC Screening

CT colonography or virtual colonoscopy is a fairly new modality that has the potential to play a significant role in screening for colon cancer. CT colonography is an attractive option for two specific reasons. First, it is non-invasive and, second, it obviates the need for sedation. It thus overcomes the two major drawbacks of optical colonoscopy. CT colonography cannot be a stand-alone technique for colorectal cancer screening because, unlike conventional colonoscopy, it does not possess a therapeutic option or a definite diagnostic capability. However, CT colonography can be a cost-effective complement to traditional colonoscopy if it is reasonably priced and if appropriate cut-off levels (>6 mm polyp) are used to increase its sensitivity.     

Detection of colorectal polyps by multislice CT colonography with ultra-low-dose technique: comparison with high-resolution videocolonoscopy

BACKGROUND: This prospective study compared multislice CT colonography with ultra-low-dose technique to high-resolution videocolonoscopy as the standard for detection of colorectal cancer and polyps. METHODS: After standard bowel preparation, 115 patients underwent multislice CT colonography with an ultra-low-dose multislice CT colonography protocol immediately before videocolonoscopy. After noise reduction by using a mathematical algorithm, ultra-low-dose multislice CT colonographic images were analyzed in blinded fashion, and the results were compared with the results of high-resolution videocolonoscopy. RESULTS: A total of 150 lesions were detected by high-resolution videocolonoscopy in 115 patients. For ultra-low-dose multislice CT colonography, sensitivities for detection of polyps less than 5 mm in size, 5 to 10 mm, and greater than 10 mm in diameter were 76%, 91%, and 100%, respectively. Although the sensitivity for detection of flat lesions was only 50%, the sensitivity and the specificity for detection of polyps 5 mm or greater in size were 94% and 84%, respectively. For adenomatous lesions greater than 5 mm in size, sensitivity was 94% and specificity was 92%. The overall specificity was 79%. The calculated effective radiation dose ranged between 0.75 and 1.25 mSv. CONCLUSIONS: Compared with high-resolution videocolonoscopy, ultra-low-dose multislice CT colonography has excellent sensitivity and specificity for detection of colorectal lesions 5 mm or greater in size, and the radiation exposure is relatively low. However, before this technique can be generally recommended for colorectal screening, further improvement in the detection of flat and extremely small lesions must be achieved.     

Virtual CT colonoscopy and virtual CT barium enema using multidetector-row CT]

CT colonography is a promising technique that provides both multiplanar and endoluminal perspective of the air-filled, distended, cleaned colon. "Virtual colonoscopy" refers to computer-simulated 3D endoscopic visualization of the colonic mucosal surface. Unlike barium enema and conventional colonoscopy, CT colonography can give cross- sectional and endoluminal images of the colon and enables to image extracolic abnormality. CT colonography offers potential advantages over colonoscopy in that it causes little discomfort to the patient, and does not need sedation. It is more accurate in spatial location of lesions and creates no complication. To date, most studies assessing CT colonography have focused in technical development, less aggressive bowel preparation, and computer-aided diagnosis of polyp detection. In the future, CT colonography would be a diagnostic and screening tool for the colorectal polyp and cancer.     

Performance of multidetector computed tomography colonography compared with conventional colonoscopy

BACKGROUND AND AIMS: This was a prospective blinded study to compare computed tomography (CT) colonography, performed with multidetector arrays CT scan (MDCT), with conventional colonoscopy for the detection of colorectal neoplasia. METHODS: Fifty patients were examined by MDCT after standard bowel preparation and rectal air insufflation in the supine and prone positions. Data sets were examined by one radiologist and one gastroenterologist blinded to the patient's history and colonoscopy results. Patients subsequently underwent colonoscopy on the same day, which served as the gold standard. RESULTS: Nine of 11 lesions >10 mm (82%), 5/15 lesions of 6-9 mm (33%), and 1/42 polyps <5 mm (3%) were detected by MDCT colonography. One false positive result for a structure larger than 10 mm was described. Nineteen of 21 patients who had no lesions during conventional colonoscopy were considered free of lesions by MDCT colonography, yielding a per patient specificity of 90%. CONCLUSION: MDCT colonography provides good data quality and has good sensitivity and specificity for the detection of colonic lesions of 10 mm or more.     

Computerized tomographic colonography: performance evaluation in a retrospective multicenter setting

BACKGROUND & AIMS: No multicenter study has been reported evaluating the performance and interobserver variability of computerized tomographic colonography. The aim of this study was to assess the accuracy of computerized tomographic colonography for detecting clinically important colorectal neoplasia (polyps >or=10 mm in diameter) in a multi-institutional study. METHODS: A retrospective study was developed from 341 patients who had computerized tomographic colonography and colonoscopy among 8 medical centers. Colonoscopy and pathology reports provided the standard. A random sample of 117 patients, stratified by criterion standard, was requested. Ninety-three patients were included (47% with polyps >or=10 mm; mean age, 62 years; 56% men; 84% white; 40% reported colorectal symptoms; 74% at increased risk for colorectal cancer). Eighteen radiologists blinded to the criterion standard interpreted computerized tomography colonography examinations, each using 2 of 3 different software display platforms. RESULTS: The average area under the receiver operating characteristic curve for identifying patients with at least 1 lesion >or=10 mm was 0.80 (95% lower confidence bound, 0.74). The average sensitivity and specificity were 75% (95% lower confidence bound, 68%) and 73% (95% lower confidence bound, 66%), respectively. Per-polyp sensitivity was 75%. A trend was observed for better performance with more observer experience. There was no difference in performance across software display platforms. CONCLUSIONS: Computerized tomographic colonography performance compared favorably with reported performance of fecal occult blood testing, flexible sigmoidoscopy, and barium enema. A prospective study evaluating the performance of computerized tomography colonography in a screening population is indicated.     

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.     

MR-colonography in hospitalized patients: feasibility and sensitivity

INTRODUCTION: Besides conventional colonoscopy, CT and MR colonography offer alternate virtual imaging modalities of the colon. The sensitivity of CT colonography, which is associated with radiation exposure, has been published in prior, large studies. Regarding MR colonography, in particular dark lumen MR colonography with the rectal administration of a water enema as a contrast agent, only limited published data exist. The goal of this study was to compare MR colonography with conventional colonoscopy in the detection of colorectal polyps. In addition the feasibility and image quality in unselected hospitalised patients were assessed. PATIENTS/METHODS: Included were 103 hospitalised patients who had to undergo colonoscopy for various indications. Immediately prior to conventional colonoscopy, MR colonography with rectal water enema and additional intravenous administration of contrast material was performed. Detection rates for polyps and adenomas were documented with both imaging modalities. Image quality and completion rates (practicability) and other (incidental) findings were also recorded. RESULTS: In 15 of 103 patients the MR examination could not be done or was only partially completed. The detection rate of MR colonography for polyps (adenomas) was 2% (4%) for polyps (adenomas) up to 5 mm in diameter, 38% (56%) for polyps (adenomas) 6-10 mm in diameter and 89% (89%) for polyps (adenomas) up to 11 mm in diameter. One flat carcinoma seen with conventional coloscopy was missed on MR colonography. CONCLUSIONS: MR colonography offers the possibility of imaging the colon without exposure to radiation. Polyps and adenomas are detected, similar to the detection rate of CT colonography, with adequate sensitivity only if they are larger than 10 mm in diameter. Therefore this imaging technique is not (yet) suitable as a screening test. Additional limitations are the necessary cooperation of the patient which can reduce the practicability and image quality in selected patients. Further studies like the just started German multicentre trial are needed to assess the position of MR colonography.