Missed Lesions and False-Positive Findings on Computed-Tomographic Colonography: a Controlled Prospective Analysis

Background and Study Aims: The aim of the present study was to analyze the reasons for false findings on computed-tomographic (CT) colonography.
Patients and Methods: A total of 100 consecutive CT colonography examinations were carried out before conventional colonoscopies scheduled on the same day. Before the study, an experienced radiologist received training in analyzing CT colonographies. The radiologists and endoscopists were blinded to each others’ findings. The patients received standard polyethylene glycol bowel preparation and were scanned in the prone and supine positions using a helical CT scanner and commercially available software for image analysis. Each pair of examinations was later followed by an unblinded analysis, comparing the CT colonographies with video recordings of the conventional colonographies in order to determine the reasons for tumors being missed or false-positive diagnoses arising on CT colonography.
Results: Ninety polyps were detected in 41 patients. For patients with tumors ≥ 5 mm and ≥ 10 mm, the sensitivity was 67 % and 75 %, respectively, and the specificity was 84 % and 95 %, respectively. The most important reasons for the 38 false findings of tumors ≥ 5 mm were perception errors (21 of 38) and misinterpretation of flat lesions in particular, including a high-grade dysplasia and a flat elevated Dukes A carcinoma. Residual stool was frequently the reason for misinterpreting lesions ≥ 10 mm (four of 10).
Conclusions: Perception errors were the main reason for false findings of lesions ≥ 5 mm, including one flat malignant lesion. Residual stool caused four of 10 false findings for lesions ≥ 10 mm. Reading CT colonographies requires a high level of expertise, and conventional colonography is still regarded as the gold standard for detecting colorectal lesions.

References

• 1 Greenlee R T, Hill-Harman M B, Murray T, Thun M. Cancer statistics.  CA Cancer J Clin. 2001;  51 15-36
• 2 Morson B C. Genesis of colorectal cancer.  Clin Gastroenterol. 1976;  5 505-525
• 3 Kronborg O, Fenger C, Olsen J. et al . Randomised study of screening for colorectal cancer with faecal occult blood test.  Lancet. 1996;  348 1467-1471
• 4 Hardcastle J D, Chamberlain J O, Robinson M H. et al . Randomised controlled trial of faecal occult blood screening for colorectal cancer.  Lancet. 1996;  348 1472-1477
• 5 Mandel J S, Bond J H, Church T R. et al . Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study.  N Engl J Med. 1993;  328 1365-1371
• 6 Winawer S J, Zauber A G, Ho M N. et al . Prevention of colorectal cancer by colonoscopic polypectomy. The National Polyp Study Workgroup.  N Engl J Med. 1993;  329 1977-1981
• 7 Jorgensen O D, Kronborg O, Fenger C. A randomised study of screening for colorectal cancer using fecal occult blood testing: results after 13 years and biennial screening.  Gut. 2002;  50 29-32
• 8 Winawer S J, Stewart E T, Zauber A G. et al . A comparison of colonoscopy and double-contrast barium enema for surveillance after polypectomy. National Polyp Study Work Group.  N Engl J Med. 2000;  342 1766-1772
• 9 Jentschura D, Raute M, Winter J. et al . Complications in endoscopy of the lower gastrointestinal tract: therapy and prognosis.  Surg Endosc. 1994;  8 672-676
• 10 Fletcher J G, Johnson C D, MacCarty R L. et al . CT colonography: potential pitfalls and problem-solving techniques.  AJR Am J Roentgenol. 1999;  172 1271-1278
• 11 Gluecker T M, Fletcher J G, Welch T J. et al . Characterization of lesions missed on interpretation of CT colonography using a 2D search method.  AJR Am J Roentgenol. 2004;  182 881-889
• 12 Pickhardt P J, Nugent P A, Choi J R, Schindler W R. Flat colorectal lesions in asymptomatic adults: implications for screening with CT virtual colonoscopy.  AJR Am J Roentgenol. 2004;  183 1343-1347
• 13 Arnesen R B, Adamsen S, von Benzon E. et al . CT colonography compared with conventional colonoscopy: a feasibility study of diagnostic performance and image-analysis in 110 patients.  Endoscopy. 2001;  33 (Suppl I = CD-ROM issued with Vol. 33)
• 14 Altman D G. Practical statistics for medical research. London; Chapman and Hall 1996: 229-259, Abstr. 2769
• 15 Arnesen R B, Adamsen S, Raaschou H O. et al . CT colonography (virtual colonoscopy) compared with colonoscopy in 231 paired examinations [abstract].  Gastrointest Endosc. 2002;  55 AB467
• 16 Arnesen R B, Adamsen S, Raaschou H O, Hansen O H. CT colonography (virtual colonoscopy) causes less discomfort, but patients still prefer colonoscopy: a paired prospective study.  Gastrointest Endosc. 2003;  57 W1170
• 17 Rex D K, Cutler C S, Lemmel G T. et al . Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies.  Gastroenterology. 1997;  112 24-28
• 18 Edwards J T, Mendelson R M, Fritschi L. et al . Colorectal neoplasia screening with CT colonography in average-risk asymptomatic subjects: community-based study.  Radiology. 2004;  230 459-464
• 19 Pickhardt P J, Choi J R, Hwang I. et al . Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults.  N Engl J Med. 2003;  349 2191-2200
• 20 Cotton P B, Durkalski V L, Pineau B C. et al . Computed tomographic colonography (virtual colonoscopy): a multicenter comparison with standard colonoscopy for detection of colorectal neoplasia.  JAMA. 2004;  291 1713-1739
• 21 Kay C L, Kulling D, Hawes R H. et al . Virtual endoscopy: comparison with colonoscopy in the detection of space-occupying lesions of the colon.  Endoscopy. 2000;  32 226-232
• 22 Mendeleson R M, Foster N M, Edwards J T. et al . Virtual colonoscopy compared with conventional colonoscopy: a developing technology.  Med J Austr. 2000;  173 472-475
• 23 Rex D K, Vining D J, Kopecky K K. An initial experience with screening for colon polyps using spiral CT with and without CT colonography (virtual colonoscopy).  Gastrointest Endosc. 1999;  50 309-313
• 24 Pescatore P, Glucker T, Delarive J. et al . Diagnostic accuracy and interobserver agreement of CT colonography (virtual colonoscopy).  Gut. 2000;  47 126-130
• 25 Hoppe H, Netzer P, Spreng A. et al . 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.  Am J Gastroenterol. 2004;  99 1924-1935
• 26 Fenlon H M, Nunes D P, Schroy P C. et al . A comparison of virtual and conventional colonoscopy for the detection of colorectal polyps.  N Engl J Med. 1999;  341 1496-1503
• 27 Fletcher J G, Johnson C D, Welch T J. et al . Optimization of CT colonography technique: prospective trial in 180 patients.  Radiology. 2000;  216 704-711
• 28 Morrin M M, Farrell R J, Kruskal J B. et al . Utility of intravenously administered contrast material at CT colonography.  Radiology. 2000;  217 765-771
• 29 Laghi A, Iannaccone R, Carbone I. et al . Detection of colorectal lesions with virtual computed tomographic colonography.  Am J Surg. 2002;  183 124-131
• 30 Ginnerup Pedersen B, Christiansen T EM, Bjerregaard N C. et al . Colonoscopy and multidetector-array computed-tomographic colonography: detection rates and feasibility.  Endoscopy. 2003;  35 736-742
• 31 Laghi A, Iannaccone R, Carbone I. et al . Computed tomographic colonography (virtual colonoscopy): blinded prospective comparison with conventional colonoscopy for the detection of colorectal neoplasia.  Endoscopy. 2002;  34 441-446
• 32 Yee J, Akerkar G A, Hung R K. et al . Colorectal neoplasia: performance characteristics of CT colonography for detection in 300 patients.  Radiology. 2001;  219 685-692
• 33 Hara A K, Johnson C D, MacCarty R L. et al . CT colonography: single- versus multi-detector row imaging.  Radiology. 2001;  219 461-465
• 34 Gluecker T, Dorta G, Keller W. et al . Performance of multidetector computed tomography colonography compared with conventional colonoscopy.  Gut. 2002;  51 207-211
• 35 Fujii T, Rembacken B J, Dixon M F. et al . Flat adenomas in the United Kingdom: are treatable cancers being missed.  Endoscopy. 1998;  30 437-443
• 36 Rembacken B J, Fujii T, Cairns A. et al . Flat and depressed colonic neoplasms: a prospective study of 1000 colonoscopies in the UK.  Lancet. 2000;  355 1211-1214
• 37 Ginnerup Pedersen B, Christiansen T EM, Mortensen F V. et al . Bowel cleansing methods prior to CT colonography.  Acta Radiol. 2002;  43 306-311
• 38 Macari M, Lavelle M, Pedrosa I. et al . Effect of different bowel preparations on residual fluid at CT colonography.  Radiology. 2001;  218 274-277
• 39 Zalis M, Hahn P F. Digital subtraction bowel cleansing in CT colonography.  AJR Am J Roentgenol. 2001;  176 646-648
• 40 Fenlon H M, McAneny D B, Nunes D P. et al . Occlusive colon carcinoma: virtual colonoscopy in the preoperative evaluation of the proximal colon.  Radiology. 1999;  210 423-428
• 41 Morrin M M, Kruskal J B, Farrell R J. et al . Endoluminal CT colonography after an incomplete endoscopic colonoscopy.  AJR Am J Roentgenol. 1999;  172 913-918
• 42 Macari M, Berman P, Dicker M. et al . Usefulness of CT colonography in patients with incomplete colonoscopy.  AJR Am J Roentgenol. 1999;  173 561-564
• 43 Iannaccone R, Laghi A, Catalano C. et al . Computed tomographic colonography without cathartic preparation for the detection of colorectal polyps.  Gastroenterology. 2004;  127 1300-1311
• 44 Taylor S A, Halligan S, Vance M. et al . Use of multidetector-row computed tomographic colonography before flexible sigmoidoscopy in the investigation of rectal bleeding.  Br J Surg. 2003;  90 1163-1164
• 45 Dixon G D. Computerized tomographic screening - are we doing it right? I think not!.  Mo Med. 2003;  100 124-127
• 46 Hur C, Gazelle G S, Zalis M E, Podolsky D K. An analysis of the potential impact of computed tomographic colonography (virtual colonoscopy) on colonoscopy demand.  Gastroenterology. 2004;  127 1312-1321