CT Virtual Colonoscopy: Role in management of colorectal polyps

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

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  • CT Virtual Colonoscopy: Role in management of colorectal polypsDepartment of SurgeryRuttonjee & TSK HospitalsDr KY Wong

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Colorectal cancerThe second most common cancer in HK2003 incidence was 2095 with 854 deaths10% of all new cancer cases7.8% of all cancer deathHighly treatable disease if diagnosed early

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Natural historyPrecursor of 90% of colorectal cancer is the adenomatous polyp, adenoma to carcinoma sequencePolyp size correlates to cancer riskPolyps < 1cm 1% are cancerousPolyps > 2cm 30% are cancerous

    T Muto et al. Evolution of CRC. Cancer 1975MJ Hill et at. Etiology of adenoma-carcinoma sequence. Lancet 1978

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Early detection of colorectal cancerDetection and removal of polyps has been shown to reduce incidence of CRCColonoscopy remains the gold standard in management of colonic polyps

    F Citarda et al. Colonoscopic polypectomy in reducing CRC incidence. Gut 2001J Sidney et al. Prevention of CRC by colonoscopic polypectomy. N Eng J Med 1993DK Rex et al. Sensitivity of colonoscopy vs Ba enema in CRC. Gastroenterology 1997

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Limitation of colonoscopyInvasive procedureRequires sedationPoor patients complianceRisk of complicationsIncomplete examination in 5% of casesSignificant 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 ColonoscopyIn 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 colonoscopyThey called this the Virtual ColonoscopyDJ 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

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

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Scanning methodHelical 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 artifactsAK Hara et al. CT colonoscopy: single vs multi-detector row imaging. Radiology 2001.

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Supination and pronationChanging position can redistribute the gas and fluid into previous collapsed segment and increase polyps detection rateAP Royster et al. CT colonoscopy techniques. AJR 1997.

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Data processingData processing is performed with a commercially available softwareImages 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

  • 2D imageCan be quicker to read than a Virtual colonoscopyPathology is better delineatedlung windows useful for smaller polypssoft tissue windows also useful

    Department of Surgery, Ruttonjee & TSK Hospitals

  • 3D imageForwardBackward

    On forward view, polyp is not seen; however when a reverse colonoscopy is simulated, polyp is easily seen

    Department of Surgery, Ruttonjee & TSK Hospitals

  • 2D + 3D imagesMost centers rely on 2D image for initial interpretation and reserving 3D luminal view for problem solving as to decreases false positive rateMost centers now use Multiplanar Reformation views in which all different 2D cuts can be seen juxtaposed with 3D imagesM 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

  • Other potential usesTo screen the remaining colon in incomplete colonoscopy due to tortuosityTo screen the proximal colon in obstructed cancerAccurate location of cancer positionExtracolonic and incidental findings

    M Helen et al. Occlusive cancer: virtual colonoscopy in pre-op evaluation. Radiology 1999H Mikael et al. Extracolonic and incidental findings on CT colonoscopy. AJR 2004

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Other potential usesPreoperative T and N staging of CRC with IV contrast CT colonoscopyDetection of colonic stenosis in Crohns colitis

    A Filippone et al. Pre-op T & N staging in CRC: contrast enhanced CT colonoscopy. Radiology 2004Y Ota et al. Value of CT colonoscopy in Crohns colitis. Abdominal imaging 2003

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Results of polyps detection(Vs colonoscopy )

    StudyPatientSensitivity ( % )Specificity ( % )Patient characteristic>10mm6-9mm10mm6-9mm

  • Results of polyps detection(Vs colonoscopy )

    Department of Surgery, Ruttonjee & TSK Hospitals

  • RHTSK- background>500 colonoscopies performed per yearCommon indication: surveillance for colorectal polypsLong waiting list for colonoscopyNew multidetector CT scanner is available recently? Can CT virtual colonoscopy share the workload of colonoscopy

    Department of Surgery, Ruttonjee & TSK Hospitals

  • RHTSK- patient and methodPatients with bowel symptoms and require colonoscopy for investigation between June to Sept 2004Bowel preparation with 2L Klean prepFecal tagging agent is givenCT colonoscopy followed by conventional colonoscopyBoth 2D and 3D images are created and reviewed by radiologistsCT colonoscopic findings are correlated with standard colonoscopic findingsBoth investigators are blinded from the results

    Department of Surgery, Ruttonjee & TSK Hospitals

  • RHTSK- resultsN: 51 ( M:F = 24:17 ); ( mean age: 61.9 years )Results:Normal study in 27 patients19 adenomas and 6 cancer were detectedOverall 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 preparation15 patients had 20 extracolonic findings of moderate to high importanceRenal stones, bladder stone, hydronephrosis, AAA, GS, ductal stone, cirrhosis, liver abscess, liver and lung secondary

    Department of Surgery, Ruttonjee & TSK Hospitals

  • Limitation of CT colonoscopyRelatively low sensitivity and specificity for polyps < 5mmSignificant false positive polyps detection rateProblem in detection of flat adenomaRelatively lengthy data interpretation time- 20minRadiation exposureCost

    Department of Surgery, Ruttonjee & TSK Hospitals

  • ConclusionSurveillance of colonic polyps can reduce CRC incidenceColonoscopy remains the gold standard for management of colonic polyps but has limitationCT 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

  • ConclusionIt can share the workload of colonoscopy in surveillance of colonic polyps especially for those patient reluctant for colonoscopy and had incomplete colonoscopy beforeFurther development and studies require to solve the problems of false +ve rate and flat adenoma

    Department of Surgery, Ruttonjee & TSK Hospitals

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