CT Virtual Colonoscopy: Role in management of colorectal polyps

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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

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

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

16. 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

17. 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

18. Results of polyps detection(Vs colonoscopy ) Department of Surgery, Ruttonjee & TSK Hospitals

19. Results of polyps detection(Vs colonoscopy ) Department of Surgery, Ruttonjee & TSK Hospitals

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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