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CT colonography to detect colorectal polyps: a virtual success?
210
World Literature Review
present options for treating patients who are seen for a complaint of continued sensation of incomplete evacuation. Timothy R. Koch, M.D. Division of Gastroenterology and Hepatology Digestive Disease Center Medical College of Wisconsin, Milwaukee, Wisconsin
REFERENCES 1. Fass R, Longstreth GF, Pimentel M, et al. Evidence- and consensus-based practice guidelines for the diagnosis of irritable bowel syndrome. Arch Intern Med 2001;161:2081–8. 2. Jailwala J, Imperiale TF, Kroenke K. Pharmacologic treatment of the irritable bowel syndrome: A systematic review of randomized, controlled trials. Ann Intern Med 2000;133:136 –47. 3. Bouin M, Plourde V, Boivin M, et al. Rectal distention testing in patients with irritable bowel syndrome: Sensitivity, specificity, and predictive values of pain sensory thresholds. Gastroenterology 2002;122:1771–7. 4. Leroi A-M, Berkelmans I, Denis P, et al. Anismus as a marker of sexual abuse: Consequences of abuse on anorectal motility. Dig Dis Sci 1995;40:1411–6.
CT Colonography to Detect Colorectal Polyps: A Virtual Success? Yee J, Akerkar GA, Hung RK, et al. Colorectal Neoplasia: Performance Characteristics of CT Colonography for Detection in 300 Patients Radiology 2001;219(3):685–92
ABSTRACT The purpose of this study was to determine the sensitivity and specificity of CT colonography (CTC) to detect colorectal polyps and cancer compared with conventional colonoscopy. In this investigation, 300 patients (97% male; mean age 62.6 yr) at a university-affiliated Veterans Affair hospital were recruited to undergo CTC 2–3 h before a clinically indicated conventional colonoscopy. Colonic lavage was achieved with 10 oz of magnesium citrate and 4 L of a polyethylene glycol electrolyte lavage solution; colonic distention was performed using hand-bulb insufflation of air. Volumetric data were acquired under 60 s using a single-slice spiral CT scan of the abdomen and pelvis in the supine position, and repeated in the prone position. Lesion size at CTC was determined by measuring the largest diameter with computed calipers; polyp size at conventional colonoscopy was estimated in reference to open biopsy forceps. The study population consisted of 204 subjects undergoing evaluation of gastrointestinal symptoms and 96 for colorectal neoplasia screening. Conventional colonoscopy found a total of 532 lesions, including eight cancers. The ability of CTC to identify individual lesions, as well as patients with lesions, was proportional to the lesion size. For individual lesion detection, the overall sensitivity of CTC was 69.7%; however, the sensitivity for lesions 5–9.9 mm and those 10
AJG – Vol. 98, No. 1, 2003
mm or greater were 80.1% and 90%, respectively (82% and 94% respectively for adenomas). All eight cancers were detected. For detecting lesions of any size, the sensitivity and specificity were 90.1 and 72% respectively. CT colonography was more accurate in identifying patients with lesions 5–9.9 mm and those with lesions ⱖ10 mm with sensitivities of 93 and 100% respectively. The results were comparable between asymptomatic and symptomatic patients. CT colonography demonstrated 185 false-positive lesions in 113 patients, 24 ⱖ1 cm and 97 of 5–9.9 mm in size; it failed to detect eight polyps of size 10 mm or greater and 28 polyps measuring 5–9.9 mm. Inadequate bowel preparation appeared to be a greater factor than poor colonic distention. The authors conclude that CTC has excellent sensitivity for clinically important polyps of 10 mm or greater and can reliably detect colorectal cancers equally well in symptomatic and asymptomatic patients. (Am J Gastroenterol 2003; 98:210 –211. © 2003 by Am. Coll. of Gastroenterology)
COMMENT Colorectal cancer screening is effective yet remains underutilized. Based on 1999 data from the Behavioral Risk Factor Surveillance System, only 32% of adults over the age of 50 yr reported having either a flexible sigmoidoscopy or colonoscopy within the preceding 5 yr (1). CT colonography is a minimally invasive procedure, has no reported complications to date, and does not require conscious sedation. These favorable factors are appealing to potential patients and could lead to increased compliance with colorectal cancer screening recommendations (2). The accuracy of virtual colonoscopy in detecting colorectal lesions requires further evaluation before it can be endorsed as an alternative to current screening modalities. In this report, Yee and colleagues report a CTC miss rate of 18% for adenomas 5–9.9 mm and 6% for adenomas 10 mm or greater. Rex et al. reported similar results for adenomas missed by colonoscopy; at the higher cutoff size of 6 –9 mm, the miss rate was 13%, whereas 6% of adenomas 10 mm or greater were missed (3). Because of the imperfection of the reference standard, there remains a possibility that lesions labeled as false positive by CTC could be true lesions missed by colonoscopy. To minimize this possibility, segmental unblinding with reassessment of questionable areas on CTC has been proposed (4). Because the role of CTC is to identify individuals who need a colonoscopy, a better unit of analysis may be the identification of patients with lesions above a critical size value. When analyzed in this fashion, the sensitivity of CTC in this study improves to 93% for patients with lesions 5–9.9 mm and 100% for those 10 mm or greater.
AJG – January, 2003
However, significant controversy remains regarding what constitutes an appropriate cutoff size. Of importance, the authors found CTC to be equally efficacious in the asymptomatic group that is more representative of a screening population. The results reported by Yee et al. compare with the best of the larger studies reported to date (5–7). In these studies, individual lesion detection by CTC varied between 47– 82% for those 6 –9 mm and 73–92% for 10 mm or greater; detection of patients with lesions 6–9 mm varied between 63– 88% and 75–96% for patients with lesions 10 mm or greater. Several factors could explain these varying results, including differences in technologies such as CT scanners and computer software, varying data acquisition techniques, different bowel preparations, patient factors (age, weight, body habitus, bowel habits), as well as inconsistent study designs. This report shows that CTC performed in an expert center can be a highly accurate colorectal cancer screening method. If these results can consistently be reproduced, CTC may become a preferred colorectal cancer screening modality in light of its limited invasiveness. Benoit C. Pineau, M.D., M.Sc.(Epid.), F.R.C.P.C. Department of Medicine David J. Ott, M.D., F.A.C.G. Department of Radiology Wake Forest University School of Medicine Winston-Salem, North Carolina
REFERENCES 1. Smith RA, von Eschenbach AC, Wender R, et al. American Cancer Society guidelines for the early detection of cancer: Update of early detection guidelines for prostate, colorectal, and endometrial cancers. CA Cancer J Clin 2001;51:38 –75. 2. Angtuaco TL, Banaad-Omiotek GD, Howden CW. Differing attitudes toward virtual and conventional colonoscopy for colorectal cancer screening: Surveys among primary care physicians and potential patients. Am J Gastroenterol 2001;96:887–93. 3. Rex DK, Cutler CS, Lemmel GT, et al. Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies. Gastroenterol 1997;112:24 –8. 4. Pineau BC, Paskett ED, Chen GJ, et al. Validation of virtual colonoscopy in the detection of colorectal polyps and masses: Rationale for proper study design. IJGC 2002 [in press]. 5. Hara AK, Johnson DC, Reed JE, et al. Detection of colorectal polyps with CT colography: Initial assessment of sensitivity and specificity. Radiology 1997;205:59 –65. 6. Fenlon HM, Nunes DP, Schroy PC, III, et al. A comparison of virtual and conventional colonoscopy for the detection of colorectal polyps [erratum in N Engl J Med 2000 Feb 17;342(7): 524]. N Engl J Med 1999;341:1496 –1503. 7. Fletcher JG, Johnson CD, Welch TJ, et al. Optimization of CT colonography technique: Prospective trial in 180 patients. Radiology 2000;216:704 –11.
World Literature Review
211
MR Imaging of Crohn’s Disease: What is the Attraction? Koh DM, Miao Y, Chinn RJS, et al. MR Imaging Evaluation of the Activity of Crohn’s Disease. AJR 2001;177:1325–32
ABSTRACT The purpose of this study was to evaluate the efficacy of MR imaging in assessing the activity of Crohn’s disease. Activity assessment is important in this disorder to identify patients with active inflammation so that optimal and newer forms of therapy can be prescribed appropriately (1–3). In this investigation, 30 symptomatic patients with Crohn’s disease but of uncertain activity were prospectively examined using MR imaging; 29 patients were scored using a Crohn’s disease activity index (2). MR findings were correlated with the activity index and also with endoscopy, surgery, or both in all patients. A multiphasic MR examination was performed using a variety of T1 and T2 techniques along with gadoliniumenhanced sequences; patients also ingested 600 cc of water for bowel contrast and were given 1 mg of glucagon to lessen bowel wall activity. Images were assessed by two radiologists who were not aware of the patient’s symptoms, clinical scoring, or results of other imaging; a consensus agreement was reached in each patient regarding the absence or presence of active disease overall per patient and also in specifically identified segments of the gastrointestinal tract. Results showed that 23 patients had active disease and seven patients had inactive disease as determined by endoscopic and/or surgical findings. MR findings in 124 of a total of 168 bowel segments were correlated to the endoscopic or surgical results. MR imaging had an overall sensitivity of 91% and a specificity of 71% on a per patient basis; the Crohn’s disease activity index showed 92% sensitivity and 28% specificity, while the per bowel segment results were 59% and 93%, respectively. Bowel wall thickening of more than 4 mm, bowel wall enhancement, and increased mesenteric vascularity were useful in identifying active disease on MR imaging; also, a layered enhancement pattern after gadolinium imaging was highly specific for active inflammation. The authors conclude that MR imaging is useful in assessing the activity of Crohn’s disease and may be helpful when clinical scoring is equivocal. (Am J Gastroenterol 2003;98:211–212. © 2003 by Am. Coll. of Gastroenterology)
COMMENT Although the role of MR imaging in evaluating perianal fistulas is well established, its use in imaging Crohn’s disease of the small bowel and colon is still evolving (4 – 8). MR imaging of the gastrointestinal tract has improved in
World Literature Review
present options for treating patients who are seen for a complaint of continued sensation of incomplete evacuation. Timothy R. Koch, M.D. Division of Gastroenterology and Hepatology Digestive Disease Center Medical College of Wisconsin, Milwaukee, Wisconsin
REFERENCES 1. Fass R, Longstreth GF, Pimentel M, et al. Evidence- and consensus-based practice guidelines for the diagnosis of irritable bowel syndrome. Arch Intern Med 2001;161:2081–8. 2. Jailwala J, Imperiale TF, Kroenke K. Pharmacologic treatment of the irritable bowel syndrome: A systematic review of randomized, controlled trials. Ann Intern Med 2000;133:136 –47. 3. Bouin M, Plourde V, Boivin M, et al. Rectal distention testing in patients with irritable bowel syndrome: Sensitivity, specificity, and predictive values of pain sensory thresholds. Gastroenterology 2002;122:1771–7. 4. Leroi A-M, Berkelmans I, Denis P, et al. Anismus as a marker of sexual abuse: Consequences of abuse on anorectal motility. Dig Dis Sci 1995;40:1411–6.
CT Colonography to Detect Colorectal Polyps: A Virtual Success? Yee J, Akerkar GA, Hung RK, et al. Colorectal Neoplasia: Performance Characteristics of CT Colonography for Detection in 300 Patients Radiology 2001;219(3):685–92
ABSTRACT The purpose of this study was to determine the sensitivity and specificity of CT colonography (CTC) to detect colorectal polyps and cancer compared with conventional colonoscopy. In this investigation, 300 patients (97% male; mean age 62.6 yr) at a university-affiliated Veterans Affair hospital were recruited to undergo CTC 2–3 h before a clinically indicated conventional colonoscopy. Colonic lavage was achieved with 10 oz of magnesium citrate and 4 L of a polyethylene glycol electrolyte lavage solution; colonic distention was performed using hand-bulb insufflation of air. Volumetric data were acquired under 60 s using a single-slice spiral CT scan of the abdomen and pelvis in the supine position, and repeated in the prone position. Lesion size at CTC was determined by measuring the largest diameter with computed calipers; polyp size at conventional colonoscopy was estimated in reference to open biopsy forceps. The study population consisted of 204 subjects undergoing evaluation of gastrointestinal symptoms and 96 for colorectal neoplasia screening. Conventional colonoscopy found a total of 532 lesions, including eight cancers. The ability of CTC to identify individual lesions, as well as patients with lesions, was proportional to the lesion size. For individual lesion detection, the overall sensitivity of CTC was 69.7%; however, the sensitivity for lesions 5–9.9 mm and those 10
AJG – Vol. 98, No. 1, 2003
mm or greater were 80.1% and 90%, respectively (82% and 94% respectively for adenomas). All eight cancers were detected. For detecting lesions of any size, the sensitivity and specificity were 90.1 and 72% respectively. CT colonography was more accurate in identifying patients with lesions 5–9.9 mm and those with lesions ⱖ10 mm with sensitivities of 93 and 100% respectively. The results were comparable between asymptomatic and symptomatic patients. CT colonography demonstrated 185 false-positive lesions in 113 patients, 24 ⱖ1 cm and 97 of 5–9.9 mm in size; it failed to detect eight polyps of size 10 mm or greater and 28 polyps measuring 5–9.9 mm. Inadequate bowel preparation appeared to be a greater factor than poor colonic distention. The authors conclude that CTC has excellent sensitivity for clinically important polyps of 10 mm or greater and can reliably detect colorectal cancers equally well in symptomatic and asymptomatic patients. (Am J Gastroenterol 2003; 98:210 –211. © 2003 by Am. Coll. of Gastroenterology)
COMMENT Colorectal cancer screening is effective yet remains underutilized. Based on 1999 data from the Behavioral Risk Factor Surveillance System, only 32% of adults over the age of 50 yr reported having either a flexible sigmoidoscopy or colonoscopy within the preceding 5 yr (1). CT colonography is a minimally invasive procedure, has no reported complications to date, and does not require conscious sedation. These favorable factors are appealing to potential patients and could lead to increased compliance with colorectal cancer screening recommendations (2). The accuracy of virtual colonoscopy in detecting colorectal lesions requires further evaluation before it can be endorsed as an alternative to current screening modalities. In this report, Yee and colleagues report a CTC miss rate of 18% for adenomas 5–9.9 mm and 6% for adenomas 10 mm or greater. Rex et al. reported similar results for adenomas missed by colonoscopy; at the higher cutoff size of 6 –9 mm, the miss rate was 13%, whereas 6% of adenomas 10 mm or greater were missed (3). Because of the imperfection of the reference standard, there remains a possibility that lesions labeled as false positive by CTC could be true lesions missed by colonoscopy. To minimize this possibility, segmental unblinding with reassessment of questionable areas on CTC has been proposed (4). Because the role of CTC is to identify individuals who need a colonoscopy, a better unit of analysis may be the identification of patients with lesions above a critical size value. When analyzed in this fashion, the sensitivity of CTC in this study improves to 93% for patients with lesions 5–9.9 mm and 100% for those 10 mm or greater.
AJG – January, 2003
However, significant controversy remains regarding what constitutes an appropriate cutoff size. Of importance, the authors found CTC to be equally efficacious in the asymptomatic group that is more representative of a screening population. The results reported by Yee et al. compare with the best of the larger studies reported to date (5–7). In these studies, individual lesion detection by CTC varied between 47– 82% for those 6 –9 mm and 73–92% for 10 mm or greater; detection of patients with lesions 6–9 mm varied between 63– 88% and 75–96% for patients with lesions 10 mm or greater. Several factors could explain these varying results, including differences in technologies such as CT scanners and computer software, varying data acquisition techniques, different bowel preparations, patient factors (age, weight, body habitus, bowel habits), as well as inconsistent study designs. This report shows that CTC performed in an expert center can be a highly accurate colorectal cancer screening method. If these results can consistently be reproduced, CTC may become a preferred colorectal cancer screening modality in light of its limited invasiveness. Benoit C. Pineau, M.D., M.Sc.(Epid.), F.R.C.P.C. Department of Medicine David J. Ott, M.D., F.A.C.G. Department of Radiology Wake Forest University School of Medicine Winston-Salem, North Carolina
REFERENCES 1. Smith RA, von Eschenbach AC, Wender R, et al. American Cancer Society guidelines for the early detection of cancer: Update of early detection guidelines for prostate, colorectal, and endometrial cancers. CA Cancer J Clin 2001;51:38 –75. 2. Angtuaco TL, Banaad-Omiotek GD, Howden CW. Differing attitudes toward virtual and conventional colonoscopy for colorectal cancer screening: Surveys among primary care physicians and potential patients. Am J Gastroenterol 2001;96:887–93. 3. Rex DK, Cutler CS, Lemmel GT, et al. Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies. Gastroenterol 1997;112:24 –8. 4. Pineau BC, Paskett ED, Chen GJ, et al. Validation of virtual colonoscopy in the detection of colorectal polyps and masses: Rationale for proper study design. IJGC 2002 [in press]. 5. Hara AK, Johnson DC, Reed JE, et al. Detection of colorectal polyps with CT colography: Initial assessment of sensitivity and specificity. Radiology 1997;205:59 –65. 6. Fenlon HM, Nunes DP, Schroy PC, III, et al. A comparison of virtual and conventional colonoscopy for the detection of colorectal polyps [erratum in N Engl J Med 2000 Feb 17;342(7): 524]. N Engl J Med 1999;341:1496 –1503. 7. Fletcher JG, Johnson CD, Welch TJ, et al. Optimization of CT colonography technique: Prospective trial in 180 patients. Radiology 2000;216:704 –11.
World Literature Review
211
MR Imaging of Crohn’s Disease: What is the Attraction? Koh DM, Miao Y, Chinn RJS, et al. MR Imaging Evaluation of the Activity of Crohn’s Disease. AJR 2001;177:1325–32
ABSTRACT The purpose of this study was to evaluate the efficacy of MR imaging in assessing the activity of Crohn’s disease. Activity assessment is important in this disorder to identify patients with active inflammation so that optimal and newer forms of therapy can be prescribed appropriately (1–3). In this investigation, 30 symptomatic patients with Crohn’s disease but of uncertain activity were prospectively examined using MR imaging; 29 patients were scored using a Crohn’s disease activity index (2). MR findings were correlated with the activity index and also with endoscopy, surgery, or both in all patients. A multiphasic MR examination was performed using a variety of T1 and T2 techniques along with gadoliniumenhanced sequences; patients also ingested 600 cc of water for bowel contrast and were given 1 mg of glucagon to lessen bowel wall activity. Images were assessed by two radiologists who were not aware of the patient’s symptoms, clinical scoring, or results of other imaging; a consensus agreement was reached in each patient regarding the absence or presence of active disease overall per patient and also in specifically identified segments of the gastrointestinal tract. Results showed that 23 patients had active disease and seven patients had inactive disease as determined by endoscopic and/or surgical findings. MR findings in 124 of a total of 168 bowel segments were correlated to the endoscopic or surgical results. MR imaging had an overall sensitivity of 91% and a specificity of 71% on a per patient basis; the Crohn’s disease activity index showed 92% sensitivity and 28% specificity, while the per bowel segment results were 59% and 93%, respectively. Bowel wall thickening of more than 4 mm, bowel wall enhancement, and increased mesenteric vascularity were useful in identifying active disease on MR imaging; also, a layered enhancement pattern after gadolinium imaging was highly specific for active inflammation. The authors conclude that MR imaging is useful in assessing the activity of Crohn’s disease and may be helpful when clinical scoring is equivocal. (Am J Gastroenterol 2003;98:211–212. © 2003 by Am. Coll. of Gastroenterology)
COMMENT Although the role of MR imaging in evaluating perianal fistulas is well established, its use in imaging Crohn’s disease of the small bowel and colon is still evolving (4 – 8). MR imaging of the gastrointestinal tract has improved in