CT colonography

Colonic Cleansing

• Dry Prep
  • 10 oz Mg Citrate
  • 45 ml Na Phosphate-contraindicated in pts with renal or cardiac failure
• Wet Prep
  • 4 liters Polyethylene Glycol

+

5 mg Bisacodyl tabs + suppository 

Colonic Distention 

• CO2 insufflation
  • High lipid solubility
  • High partial pressure gradient electronic, preset P= 25 mm HG

1. Less invasive—better patient acceptance. No six foot scope advanced to the cecum, which translates to better patient acceptance.
2. Safer: The Perforation rate 10-20x lower than colonoscopy for a diagnostic, lower for therapeutic
3. Very short procedural time. Scan in two positions: supine (lying on the back) and prone (lying on the front) that takes less than 10 seconds
4. No need for sedation which is necessary for both colonoscopy and sigmoidoscopy (looking inside the sigmoid colon and rectum).
5. Less costly than colonoscopy

Joint American Cancer Society-MSFT-ACR Screening Guidelines Average Risk Adults 50+

• Annual FOBT (fecal occult blood test)
• Flex Sigmoidoscopy every 5 years
• FOBT and Flex sigmoidoscopy
• DCBE (double contrast barium enema )every 5 years
• CT Colonography every 5 years
• Colonoscopy every 10 years 

Colorectal CA 

• Most (>95%) CRC arise in adenomatous polyps

Risk of Malignancy

• 5-9 mm 1%
• 10-20 mm 4-10%
• >20 mm 25-40%
• <10 mm polyp-invasive ca: 10 years

Adenomatous: Benign glandular tumor

Prevalence

• 25% of people by age 50
• 50-60% of people by age 80
• Villous=10x Tubular malignant potential 

CT colonography is also known as virtual colonoscopy

• 3^rd most common cancer
• 2^nd leading cause of cancer deaths in the US
• 10% of all new cancer cases
• Lifetime risk for development: 6% (1/20 will develop colon cancer)
• Lifetime risk for death: 3% (1/30 will die of colon cancer)

Take stacks of images and look through the body like flipping to the book. We can resemble and cut in different way. Good example is looking for polyps in the colon, we see 2-D images growth that can be cancer in the colon, but we resemble pixels digitally the images into 3-D of the colon.  Also, we can do a 3-D fly through movie, called CT colonography to look for polyps in the colon. By seeing it in 3-D we can locate exactly where it is.