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

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

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

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

Limitation of colonoscopy Invasive procedure Requires sedation Poor patients compliance Risk of complications Incomplete examination in 5% of cases Significant miss rate of adenoma up to 20% JB Marshall et at. Frequency of total colonoscopy. Gastrointest Endosc 1993. DK Rex et al. Colonoscopic miss rates of adenoma. Gastroenterology 1997. Department of Surgery, Ruttonjee & TSK Hospitals

CT Virtual Colonoscopy 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 They called this the “Virtual Colonoscopy” DJ Vining et al. Non-invasive colonoscopy using helical CT scanning and 3D reconstruction. 23rd annual meeting, society of GI radiologists. 1994 Department of Surgery, Ruttonjee & TSK Hospitals

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

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

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

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

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

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

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

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

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

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

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

Results of polyps detection (Vs colonoscopy ) Study Patient Sensitivity ( % ) Specificity ( % ) Patient characteristic >10mm 6-9mm <5mm AK Hara 1996 10 100 71 45 _ Symptomatic patient AK Hara 1997 70 75 66 90 63 80 HM Fenlon 1998 38 Patients with recent Dx CRC, 100% cancer detection rate HM Helen 1999 91 82 55 High risk patient Department of Surgery, Ruttonjee & TSK Hospitals

Results of polyps detection (Vs colonoscopy ) Study Patient Sensitivity ( % ) Specificity ( % ) Patient characteristic >10mm 6-9mm <5mm Yee 2001 300 90 80.1 59.1 72 ( overall ) Asymptomatic + symptomatic patients 100% cancer detection rate Carrascosa 2003 500 100 95.6 87.8 91.4 86.9 Symptomatic and high risk patients J Perry 2003 1233 93.8 93.9 88.7 96 92.2 79.6 Asymptomatic adults S Jacob 2003 1324 81 62 43 95 _ Meta-analysis Department of Surgery, Ruttonjee & TSK Hospitals

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

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

Department of Surgery, Ruttonjee & TSK Hospitals RHTSK- results N: 51 ( M:F = 24:17 ); ( mean age: 61.9 years ) 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 Renal stones, bladder stone, hydronephrosis, AAA, GS, ductal stone, cirrhosis, liver abscess, liver and lung secondary Department of Surgery, Ruttonjee & TSK Hospitals

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

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

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