Imaging the GI tract Flashcards
When would you use an ultrasound to image the GI tract?
cholelithiasis, acute cholecystitis
When are nuclear medicine scans helpful?
bile leaks
cystic duct obstruction
When should you get a KUB? What will it tell you?
Indicated for abdominal pain. Can rule out obstruction/perforation.
Why is an upright image required with a KUB?
Will show you air fluid levels in the bowel. If uneven, this tells you that PERISTALSIS is INTACT
When would you use fluoroscopy?
Pain, dysphagia, diarrhea, colon cancer screening
What are the two main methods with fluoroscopy?
- double contrast: air and barium shows mucosal detail, i.e. ulcerations, neoplasms
- Single contrast: Barium only shows peristalsis , walls, folds, caliber
When would you order an abdominal CT?
pain, bowel pathology, tumors, weight loss, vague symptoms
When would you use positive contrast (barium)?
To differentiate fluid collections from bowel
When would you use negative contrast (water, low density)
Good for evaluating bowel mucosa and wall
If you wanted to evaluate a liver met, what would you order?
CT with contrast, and “prescribed” attenuation time
When would you order an MRI to evaluate the abdomen?
AFTER an US or CT has detected an abnormality which needs more detail. OR if there are contraindications.
Exception: MRCP for Crohns
What are causes of bowel wall thickening?
infection/ischemia/neoplasm/inflammation/hemorrhage
Will see thickening of wall or loss of haustra/circularis plicae
What does CT show you with bowel thickening?
It’s sensitive, but not that specific. Can show you inflammation
Can radiography show you bowel thickening?
Yes if air filled.
What does inflamed mesenteric fat look like on CT?
"fat stranding" -Hazy -Streaky -Smudgy Sometimes enlargement. Can see this with pancreatitis
What are the imaging changes you would see with vasodilitation?
- Increased size of vessels in fat
- Bowel Mucosal hyperenhancem
- Organs have variable enhancement
What imaging changes would you see with increased extra-vascular fluid?
Increased density of fat
Decreased density or organs
Thick bowel wall folds
What are the benefits of each of the following in evaluating an inflammatory process in the abdomen?
- CT with contrast
- Radiography
- US
- MRI
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
What will you see on imaging with obstruction?
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
What is a diffuse ileus?
Absence of peristalsis, with accumulation of secretions and air in both small and large bowel. Will see air fluid levels
What are causes of a diffuse ileus?
- Post operative
- Drugs
- Adjacent inflammatory process
How will hypervascular tumors show up on CT?
earlier than the liver. Tumor will have max attenuation before the liver.
Hypovascular tumors will show up as opposite of that.
