Imaging the GI tract

Question 1

When would you use an ultrasound to image the GI tract?

Answer 1

cholelithiasis, acute cholecystitis

Question 2

When are nuclear medicine scans helpful?

Answer 2

bile leaks

cystic duct obstruction

Question 3

When should you get a KUB? What will it tell you?

Answer 3

Indicated for abdominal pain. Can rule out obstruction/perforation.

Question 4

Why is an upright image required with a KUB?

Answer 4

Will show you air fluid levels in the bowel. If uneven, this tells you that PERISTALSIS is INTACT

Question 5

When would you use fluoroscopy?

Answer 5

Pain, dysphagia, diarrhea, colon cancer screening

Question 6

What are the two main methods with fluoroscopy?

Answer 6

1. double contrast: air and barium shows mucosal detail, i.e. ulcerations, neoplasms
2. Single contrast: Barium only shows peristalsis , walls, folds, caliber

Question 7

When would you order an abdominal CT?

Answer 7

pain, bowel pathology, tumors, weight loss, vague symptoms

Question 8

When would you use positive contrast (barium)?

Answer 8

To differentiate fluid collections from bowel

Question 9

When would you use negative contrast (water, low density)

Answer 9

Good for evaluating bowel mucosa and wall

Question 10

If you wanted to evaluate a liver met, what would you order?

Answer 10

CT with contrast, and “prescribed” attenuation time

Question 11

When would you order an MRI to evaluate the abdomen?

Answer 11

AFTER an US or CT has detected an abnormality which needs more detail. OR if there are contraindications.

Exception: MRCP for Crohns

Question 12

What are causes of bowel wall thickening?

Answer 12

infection/ischemia/neoplasm/inflammation/hemorrhage

Will see thickening of wall or loss of haustra/circularis plicae

Question 13

What does CT show you with bowel thickening?

Answer 13

It’s sensitive, but not that specific. Can show you inflammation

Question 14

Can radiography show you bowel thickening?

Answer 14

Yes if air filled.

Question 15

What does inflamed mesenteric fat look like on CT?

Answer 15

"fat stranding"
-Hazy
-Streaky
-Smudgy
Sometimes enlargement. Can see this with pancreatitis

Question 16

What are the imaging changes you would see with vasodilitation?

Answer 16

1. Increased size of vessels in fat
2. Bowel Mucosal hyperenhancem
3. Organs have variable enhancement

Question 17

What imaging changes would you see with increased extra-vascular fluid?

Answer 17

Increased density of fat
Decreased density or organs
Thick bowel wall folds

Question 18

What are the benefits of each of the following in evaluating an inflammatory process in the abdomen?

1. CT with contrast
2. Radiography
3. US
4. MRI

Answer 18

CT: fast, sensitive
Xray: Non specific inflammation of organs. May see mass effect from adjacent inflammation
US: Cannot see through fat. Bad choice
MRI: expensive/costly

Question 19

What will you see on imaging with obstruction?

Answer 19

Dilation above
Decompression below
Also, little or no air in colon seen because cannot move contents along!
Strings of pearls: air trapped in plica circularis

Question 20

What is a diffuse ileus?

Answer 20

Absence of peristalsis, with accumulation of secretions and air in both small and large bowel. Will see air fluid levels

Question 21

What are causes of a diffuse ileus?

Answer 21

1. Post operative
2. Drugs
3. Adjacent inflammatory process

Question 22

How will hypervascular tumors show up on CT?

Answer 22

earlier than the liver. Tumor will have max attenuation before the liver.

Hypovascular tumors will show up as opposite of that.