CT COLONOSCOPY

Turki Alhazmi ,MB.CHB, FRCPC , dABR Interventional Radiology-Body MRI

Ass. Prof.  Faculty of MedicineUmm Al Qura University

Makkah-Saudi Arabia

Colorectal Cancers

• 3rd most common cancer in men and women

• The age range is late 40s to 70s in average-risk patients

• 20% occur in high risk genetically predisposed patients

• 80% occur sporadically in otherwise low risk individuals

“The adenoma carcinoma sequence”

“The adenoma carcinoma sequence”

“The adenoma carcinoma sequence”

risk factors for transformation into colorectal cancer through the “adenoma-

carcinomasequence

• Polyps greater than 10 mm in diameter

• >3 in number, regardless of their size

“The adenoma carcinoma sequence”

Interruption of this progression by:

detection and removal of threatening pre-cursor adenomas by endoscopic polypectomy results in a decrease of cancer related mortality by 30%

Colorectal Cancers

• Arise from pre-existing adenomatous polyp

• Requiring10–15 years

• The majority of adenomas that will develop into cancer are polypoid or villous in shape

Colorectal Cancers

The risk of an adenoma (5 mm or less )to develop into cancer is significantly low, approximating 0.9%

Screening

• Asymptomatic

• At age of 50 years

• Fecal occult blood + Colonoscopy or CTC

• Every five years, the combination of fecal occult blood and colonoscopy or CTC

• Every five years, double contrast barium enema

Screening

• Conventional colonoscopy is still the gold standard for colon cancer screening

• Cancers have also been missed by conventional colonoscopy

Screening

Why cancers are missed on conventional colonoscopy:

1.poor bowel prep

2.Slippage of the endoscope around flexures

3. redundant colon

4.misinterpretation of findings

5.failure to biopsy

Conventional ColonoscopyAdverse Outcome

• Hemorrhage & Perforation : most common

• Perforation rate 0.2 - 0.4% after diagnostic colonoscopy

• 5% increases in perforation with polypectomy

SENSETIVITY

CTC CC

10 mm polyp 93.9 % 87.5 %

8 mm polyp 93.8 % 92.3 %

6 mm polyp 88.7 % 91.5 %

SPECIFICITY

CTC CC

10 mm polyp 96 % 96.1 %

8 mm polyp 92.2 % 91.6 %

6 mm polyp 79.6 % 77.1 %

Screening

• The sensitivity and specificity per patient and per polyp were similar

• There is no statistically difference between CT COLONOSCOPY (CTC) and Conventional Colonoscopy for adenomas detection greater than 10 mm

CTC VS DCBE

sensitivity and specificity of polyp detection is higher for CTC compared to DCBE

Indications

The indications for CTC closely follow the indications for conventional optical colonoscopy with few exceptions

CTC VS CC

If you have a patient who is Elderly

With cardiovascular disease

With bleeding diathesis

With history of failed colonoscopies

CTC > CC> DCBE

CTC VS CC

• CTC is relatively fast without the need for sedation

• Less post procedure discomfort CTC than CC

Virtual disection

• Proper cleansing of the colon is essential

• Bowel cleansing for CTC is similar to barium enema and standard colonoscopy