IMAGING OF COLON CANCER

Dr. Cynthia WalshDepartment of Radiology

Objectives

To learn the imaging modality best to SCREEN for Colon Cancer

To learn the imaging modality best to SCREEN for colon polyps

To learn the imaging modality best to STAGE Colon Cancer

Outline

1. Three test questions “pre talk”2. Overview of imaging modalities for colon

cancer and colon polyps3. Double contrast barium enema4. CT Colonograpy5. CT for extracolonic pathology6. Three test questions “post talk”

Question #1

A 70 year old male has iron deficiency anemia is anticoagulated because of prior strokes. Colonoscopy requires discontinuation of anticoagulation. The neurologist does not feel that the anticoagulation should be discontinued due to the risk profile. The most appropriate imaging modality to SCREEN for colon cancer or polyps would be:

1. Double Contrast Barium Enema2. CT with IV and Oral Contrast3. CT Colonography4. Radiologist supervised ultrasound with attention to

the colon.

Question #2

An advantage of CT Colonography (CTC) over Double Contrast Barium Enema (DCBE) is:

1. CTC does not require a bowel preparation2. CTC does not use ionizing radiation3. As colon distension is not required for CTC, it

can be used in the setting of acute colitis. 4. CTC has better sensitivity and specificity for

colon polyps compared to DCBE

Question #3

A 65 year old female undergoes colonoscopy which reveals a colon cancer in the distal descending colon. The colonoscopy is incomplete as it cannot get past the mass (i.e. the colon proximal to the mass is not visualized). The most appropriate next management step is:

1. Surgical Consult for resection of the colon cancer.

2. CT with IV contrast to exclude metastases3. CT Colonography (if so…why?)4. Ultrasound to exclude liver metastases

Colon Cancer and colon polypsImaging Modality Recommended:

SCREENING - CT Colonography (if colonoscopy is incomplete,

contraindicated or not possible)- CT Colonography is a specialized CT which

focuses on the bowel. - Requires a bowel prep and colon distension

- Barium Enema nearly obsolete

STAGING of known colon cancer

- Routine CT with IV Contrast

Double Contrast Barium Enema: Colon Cancer

Double Contrast Barium Enema: pedunculated polyps

Polyp head

Polyp stalk

Double Contrast Barium Enema: - sessile polyps

CT Colonography (CTC) CT which focuses on the colon How is CTC done?

1. Requires a bowel preparation (the same as colonoscopy) Often the most difficult part of the exam

2. Rectal tube placed in rectum3. Colon distended with room air or CO2

Contraindicated in acute colitis4. Do a CT scan in TWO positions (Routine CT uses only one position)

PRO’s1. CTC is superior to Barium Enema

Better sensitivity and specificity

2. Identifies extracolonic pathology (lymphadenopathy, liver metastases)

CON: Uses ionizing radiation

CTC vs. Routine CT

Routine CT No distension of the colon No bowel preparation NOT sensitive for identifying polyps and relatively

poor for colon cancer.

Therefore, Routine CT is NOT sufficient to exclude colon polyps or cancer.

CT Colonography has largely replaced Double Contrast Barium Enema for

evaluation of colon neoplasia ( polyps and cancer )

Practices vary between institutions.

At TOH, Barium Enema is no longer performed to diagnose colonic neoplasia except under special circumstances.

CT Colonography

• Computer software traces a line through the dilated colon

CT Colonography

• Computer software traces a line through the dilated colon

3D endoluminal views

CT Colonography

• Computer software traces a line through the dilated colon

3D endoluminal views

2D images

Endoluminal View

Polyp on CT Colonography

CT Colonography- Polyp on 3D views

CT Colonography Colonoscopy

Colon Cancer on CT Colonography

Colon Cancer on CT Colonography

CT can identify extracolonic disease (Routine CT or CT Colonography)

Colon cancer

Invading the right kidney

Obstructing Cancer in the transverse colon with a liver

metastasis CT Colonography can show

colonic and extracolonic pathology

liver metastasis

Transverse colon cancer

Question #1

A 70 year old male has iron deficiency anemia is anticoagulated because of prior strokes. Colonoscopy requires discontinuation of anticoagulation. The neurologist does not feel that the anticoagulation should be discontinued due to the risk profile. The most appropriate imaging modality to SCREEN for colon cancer or polyps would be:

1. Double Contrast Barium Enema2. CT with IV and Oral Contrast3. CT Colonography4. Radiologist supervised ultrasound with attention to the

colon.

Question #2

An advantage of CT Colonography (CTC) over Double Contrast Barium Enema (DCBE) is:

1. CTC does not require a bowel preparation2. CTC does not use ionizing radiation3. As colon distension is not required for CTC, it

can be used in the setting of acute colitis. 4. CTC has better sensitivity and specificity for

colon polyps compared to DCBE

Question #3

A 65 year old female undergoes colonoscopy which reveals a colon cancer in the distal descending colon. The colonoscopy is incomplete as it cannot get past the mass (i.e. the colon proximal to the mass is not visualized). The most appropriate next management step is:

1. Surgical Consult for resection of the colon cancer.2. CT with IV contrast to exclude metastases3. CT Colonography (if so…why?)4. Ultrasound to exclude liver metastases

Question #3

A 65 year old female undergoes colonoscopy which reveals a colon cancer in the distal descending colon. The colonoscopy is incomplete as it cannot get past the mass (i.e. the colon proximal to the mass is not visualized). The most appropriate next management step is:

CT Colonography (if so…why?)

-This single test will complete screening of the colon proximal to the obstruction (i.e. exclude synchronous cancer or polyps) AND stage the malignancy (liver and nodal metastases).

Objectives

To learn the imaging modality best to screen for Colon Cancer CT Colonography (has almost replaced Double Contrast

Barium Enema)

To learn the imaging modality best to screen for colon polyps CT Colonography (has almost replaced Double Contrast

Barium Enema)

To learn the imaging modality best to stage Colon Cancer CT with IV contrast

THANK YOU