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
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. 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

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. 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

8. 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

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. 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

11. 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

12. 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

13. 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

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

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

16. 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

17. 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

18. 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

19. 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

20. 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

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. 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

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. 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

25. 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