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CT Virtual Colonoscopy: Role in management of colorectal polyps Department of Surgery Ruttonjee & TSK Hospitals Dr KY Wong.

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Presentation on theme: "CT Virtual Colonoscopy: Role in management of colorectal polyps Department of Surgery Ruttonjee & TSK Hospitals Dr KY Wong."— Presentation transcript:

1 CT Virtual Colonoscopy: Role in management of colorectal polyps Department of Surgery Ruttonjee & TSK Hospitals Dr KY Wong

2 Department of Surgery, Ruttonjee & TSK Hospitals 2 Colorectal cancer n The second most common cancer in HK n 2003 incidence was 2095 with 854 deaths n 10% of all new cancer cases n 7.8% of all cancer death n Highly treatable disease if diagnosed early

3 Department of Surgery, Ruttonjee & TSK Hospitals 3 Natural history n Precursor of 90% of colorectal cancer is the adenomatous polyp, adenoma to carcinoma sequence n Polyp size correlates to cancer risk –Polyps < 1cm – 1% are cancerous –Polyps > 2cm – 30% are cancerous n T Muto et al. Evolution of CRC. Cancer 1975 n MJ Hill et at. Etiology of adenoma-carcinoma sequence. Lancet 1978

4 Department of Surgery, Ruttonjee & TSK Hospitals 4 Early detection of colorectal cancer n Detection and removal of polyps has been shown to reduce incidence of CRC n Colonoscopy remains the gold standard in management of colonic polyps n F Citarda et al. Colonoscopic polypectomy in reducing CRC incidence. Gut 2001 n J Sidney et al. Prevention of CRC by colonoscopic polypectomy. N Eng J Med 1993 n DK Rex et al. Sensitivity of colonoscopy vs Ba enema in CRC. Gastroenterology 1997

5 Department of Surgery, Ruttonjee & TSK Hospitals 5 Limitation of colonoscopy n Invasive procedure n Requires sedation n Poor patients compliance n Risk of complications n Incomplete examination in 5% of cases n Significant miss rate of adenoma up to 20% n JB Marshall et at. Frequency of total colonoscopy. Gastrointest Endosc n DK Rex et al. Colonoscopic miss rates of adenoma. Gastroenterology 1997.

6 Department of Surgery, Ruttonjee & TSK Hospitals 6 CT Virtual Colonoscopy n In 1994, Vining and Gelfand first described the use of helical CT volumetric data to produce 3D images into a movie loop simulating the endoluminal view offered by colonoscopy n They called this the “Virtual Colonoscopy” n DJ Vining et al. Non-invasive colonoscopy using helical CT scanning and 3D reconstruction. 23 rd annual meeting, society of GI radiologists. 1994

7 Department of Surgery, Ruttonjee & TSK Hospitals 7 Patient preparation n Given bowel preparation as with colonoscopy n Fecal tagging agent- decrease false +ve rate n Rectal tube is inserted and colon is inflated with RA gently to the maximum level tolerated by patient n IV antispasmodic agent ( recent study showed unnecessary ) n A Philippe et al. Dietary fecal tagging as cleaning method. Radiology 2002 n JF Bruzzi et al. Efficacy of IV Buscopan in CT colonoscopy. Eur Radiology 2003

8 Department of Surgery, Ruttonjee & TSK Hospitals 8 Scanning method n Helical CT scanning is performed in a single breath-hold using 5mm collimation and reconstruction intervals of 2-3mm. n Acquisition is repeated with patient in prone and supine position n Multidetector CT scanners can do it all in 20 seconds- improved colonic distension and reduced respiratory artifacts n AK Hara et al. CT colonoscopy: single vs multi-detector row imaging. Radiology 2001.

9 Department of Surgery, Ruttonjee & TSK Hospitals 9 Supination and pronation n Changing position can redistribute the gas and fluid into previous collapsed segment and increase polyps detection rate n AP Royster et al. CT colonoscopy techniques. AJR 1997.

10 Department of Surgery, Ruttonjee & TSK Hospitals 10 Data processing n Data processing is performed with a commercially available software n Images included 2D ( or multiplanar reformatted ) axial images and 3D endoluminal fly-through view in both antegrade and retrograde directions

11 Department of Surgery, Ruttonjee & TSK Hospitals 11 2D image Can be quicker to read than a “ Virtual ” colonoscopy Can be quicker to read than a “ Virtual ” colonoscopy n Pathology is better delineated n lung windows useful for smaller polyps n soft tissue windows also useful

12 Department of Surgery, Ruttonjee & TSK Hospitals 12 3D image ForwardBackward On forward view, polyp is not seen; however when a reverse colonoscopy is simulated, polyp is easily seen

13 Department of Surgery, Ruttonjee & TSK Hospitals 13 2D + 3D images n Most centers rely on 2D image for initial interpretation and reserving 3D luminal view for problem solving as to decreases false positive rate n Most centers now use Multiplanar Reformation views in which all different 2D cuts can be seen juxtaposed with 3D images n M Macari et al. CT colonoscopy with 2D and 3D correlation. AJR 2001

14 Department of Surgery, Ruttonjee & TSK Hospitals 14 Virtual vs. Actual Colonoscopy

15 Department of Surgery, Ruttonjee & TSK Hospitals 15 Virtual vs. Actual Colonoscopy

16 Department of Surgery, Ruttonjee & TSK Hospitals 16 Other potential uses n To screen the remaining colon in incomplete colonoscopy due to tortuosity n To screen the proximal colon in obstructed cancer n Accurate location of cancer position n Extracolonic and incidental findings n M Helen et al. Occlusive cancer: virtual colonoscopy in pre- op evaluation. Radiology 1999 n H Mikael et al. Extracolonic and incidental findings on CT colonoscopy. AJR 2004

17 Department of Surgery, Ruttonjee & TSK Hospitals 17 Other potential uses n Preoperative T and N staging of CRC with IV contrast CT colonoscopy n Detection of colonic stenosis in Crohn’s colitis n A Filippone et al. Pre-op T & N staging in CRC: contrast enhanced CT colonoscopy. Radiology 2004 n Y Ota et al. Value of CT colonoscopy in Crohn’s colitis. Abdominal imaging 2003

18 Department of Surgery, Ruttonjee & TSK Hospitals 18 Results of polyps detection (Vs colonoscopy ) StudyPatient Sensitivity ( % ) Specificity ( % ) Patient characteristic >10mm6-9mm<5mm>10mm6-9mm<5mm AK Hara __ _ Symptomatic patient AK Hara Symptomatic patient HM Fenlon _ _ _ _ Patients with recent Dx CRC, 100% cancer detection rate HM Helen _ _ _ High risk patient

19 Department of Surgery, Ruttonjee & TSK Hospitals 19 Results of polyps detection (Vs colonoscopy ) StudyPatient Sensitivity ( % ) Specificity ( % ) Patient characteristic >10mm6-9mm<5mm>10mm6-9mm<5mm Yee ( overall ) Asymptomatic + symptomatic patients 100% cancer detection rate Carrascosa Symptomatic and high risk patients J Perry Asymptomatic adults S Jacob _ _Meta-analysis

20 Department of Surgery, Ruttonjee & TSK Hospitals 20 RHTSK- background n >500 colonoscopies performed per year n Common indication: surveillance for colorectal polyps n Long waiting list for colonoscopy n New multidetector CT scanner is available recently n ? Can CT virtual colonoscopy share the workload of colonoscopy

21 Department of Surgery, Ruttonjee & TSK Hospitals 21 RHTSK- patient and method n Patients with bowel symptoms and require colonoscopy for investigation between June to Sept 2004 n Bowel preparation with 2L Klean prep n Fecal tagging agent is given n CT colonoscopy followed by conventional colonoscopy n Both 2D and 3D images are created and reviewed by radiologists n CT colonoscopic findings are correlated with standard colonoscopic findings n Both investigators are blinded from the results

22 Department of Surgery, Ruttonjee & TSK Hospitals 22 RHTSK- results n N: 51 ( M:F = 24:17 ); ( mean age: 61.9 years ) n Results: –Normal study in 27 patients –19 adenomas and 6 cancer were detected –Overall sensitivity for adenomatous polyp detection rate is 83.3% –Sensitivity for polyp> 5mm- 9mm: 85.3% –Sensitivity for polyp< 5mm: 40% –100% cancer detection –Two false +ve polyps detected: poor bowel preparation –15 patients had 20 extracolonic findings of moderate to high importance n Renal stones, bladder stone, hydronephrosis, AAA, GS, ductal stone, cirrhosis, liver abscess, liver and lung secondary

23 Department of Surgery, Ruttonjee & TSK Hospitals 23 Limitation of CT colonoscopy n Relatively low sensitivity and specificity for polyps < 5mm n Significant false positive polyps detection rate n Problem in detection of flat adenoma n Relatively lengthy data interpretation time- 20min n Radiation exposure n Cost

24 Department of Surgery, Ruttonjee & TSK Hospitals 24 Conclusion n Surveillance of colonic polyps can reduce CRC incidence n Colonoscopy remains the gold standard for management of colonic polyps but has limitation n CT Virtual Colonoscopy is a non-invasive procedure and is comparable with standard colonoscopy for detection of clinically important polyps

25 Department of Surgery, Ruttonjee & TSK Hospitals 25 Conclusion n It can share the workload of colonoscopy in surveillance of colonic polyps especially for those patient reluctant for colonoscopy and had incomplete colonoscopy before n Further development and studies require to solve the problems of false +ve rate and flat adenoma


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