Diagnostic Imaging of GI

Question 1

On survey radiography, what should the gastric and intestinal lumen be seen to contain? Colon?

Answer 1

Gastric/SI: gas and fluid

Colon: faeces

Question 2

What can be seen more clearly using contrast radiography?

Answer 2

Masses/mucosa/gastric filling

Question 3

List 5 methods of contrast radiography of the GI tract. When would each be indicated?

Answer 3

• pnumogastrogram (FB in stomach)
• Barium meal (assess gastric emptying)
• Double contrast gastrogram (gas+barium, to identify mucosal lesions and rugae of stomach)
• Upper GI contrast study - barium series (ID stomach and intestine, GI motility, obstruction)
• Barium enema (ID colon [only with ascites*?!], intussesception, mural lesions)
  > with use of US and CT these are rarely used any more

Question 4

In what dimension should the stomach lie in a normal dog?

Answer 4

Perpendicular to spine

Question 5

What contrast medium is usually used for GI studies? Why? What else may be used?

Answer 5

Barium sulphate - ^ atomic number, bland (-> therapeutic)
> I- solution may be used, has quick intestinal transit time but may be useful when rupture of GI tract suspected as will leak easily. Doesnt coat mucosa like barium sulphate.

Question 6

How is “localised” or “focal” dilation defined? What is most likely to cause this?

Answer 6

1.6x L5 diameter or 2x rib diameter BUT not a hard and fast rule - take all clinical signs into account

Question 7

What may confused for a SI dilation?

Answer 7

Dilatued uterus due to pregnancy - will only contain foetuses from d44. Follow caudally at level of colon and if it enters the pelvic inlet then is probably uterus!

Question 8

Is lodgement of foreign material usually the cause or result of an obstruction?

Answer 8

Can be EITHER!

Question 9

What types of foreign material may be visable radiographically?

Answer 9

• metallic
• mineralised eg. stones
• rubber/plastic
• non-opaque eg. friut seeds, corn cobs (may not stand out)

Question 10

What is generalised dilation usually the result of?

Answer 10

Intestinal hypomotility eg. acute viral enteritis (parvo) electrolyte imbalance, drugs

Question 11

Will FBs always be visable on radiograph?

Answer 11

NO! -> ultrasound

Question 12

What may be seen radiographically with a partial obstruction?

Answer 12

Gravel sign - gut contents become compacted, fluid absorbed -> mineral opacity with a “corner” just before obstruction

Question 13

What may cause an abnormal luminal shape on radiograph?

Answer 13

• disordered motility eg. linear foreign body

- filling defect eg. intussecpetion, FB

Question 14

What is the stacking of intestines often seen with linear FBs referred to as?

Answer 14

Plication

Question 15

How can barium series be used to confirm suspicions of GI pathology?

Answer 15

If deformity is present at all time periods/views then most likely real rather than an artifact of the image

Question 16

How can abnormal mucosal surface be identified? What does this suggest?

Answer 16

Contrast radiography only (on radiography feaces may stick to gut wall and appear as a pathology etc.)
> suggests infiltration or ulceration

Question 17

How would an intussusception be visible on contrast radiography?

Answer 17

Long filling defect with contrast around the edges

Question 18

What disease may affect the appearance of the duodenum secondarily?

Answer 18

Pancreatitis

Question 19

Other than a pathology, what may impact gastric emptying time?

Answer 19

Stress (sympathetic innervation)

Question 20

What time period is accepted as convincing evidence of delayed gastric emptying?

Answer 20

Food in stomach 24hours after ingestion

Question 21

What is the average normal gastric emptying time for barium sulphate suspension in the dog and cat?

Answer 21

Dog 1-3hrs, 1.5hrs in pups
Cat 0.25-2hrs
very variable!!

Question 22

What is the average normal gastric emptying time for barium sulphate meal in the dog and cat?

Answer 22

Dog 4-6hrs, 3.5-7.5 in pups
Cat 4-17hrs
very variable!!

Question 23

What 3 main areas can ultrasonography assist in the assessment of?

Answer 23

GI wall
Motility
Associated organs (pancreas and LNs)

Question 24

What is the normal thickness of the GI wall? How many layers are present?

Answer 24

normal thickness 3mm (<5mm in canine duodenum and stomach)

5 layers visable

Question 25

How many peristaltic waves/min are normal?

Answer 25

4-5 (hypomotility often -> dilation)

Question 26

What are the 5 layers of intestinal wall visable on ultrasound?

Answer 26

Lumen, mucosa, submucosa, muscularis, serosa

Question 27

Which layers of the intestinal wall are hyper echoic and which are hypo?

Answer 27

• Lumen hypER
• Mucosa hypO
• Submucosa hypER
• Muscularis hypER
• Serosa mega-hypER [NB: U/S exaggerates thickness of serosa so measure from lumenal side to check thickness of gut wall]

Question 28

How may hyper-motility be seen on US?

Answer 28

Corrugation of GI tract

Question 29

What landmark is assocaited with visualising the pancreas on ultrasound?

Answer 29

Pancreaticoduodenal vein (anechoic line)

Question 30

What LN pathology is easily diagnosed by ultrasound? Can LNs be detected by any other means?

Answer 30

Lymphadenomegaly

LNs can only be visualised with ultrasound

Question 31

Is visualisation of the pancreas by US sensitive?

Answer 31

NO - changes in pancreas may not correlate to current pathology, and lack of differences on ultrasound cannot rule out pathology -> use in conjuction with other clinical signs