Imaging of the GI tract

Question 1

What is a ring down artefact?

Answer 1

Hyperechoic band distal to a a shadowing structure

Caused by exciting liquid trapped between gas bubbles

Question 2

What type of trasducer should be used for the GI tract?

Answer 2

High frequency (7.5-10)
May need lower for big dogs and deeper structures

Question 3

What are the patterns that can be produced by luminal contents?

Answer 3

Gas - hyperechoic middle
Fluid - hypoechoic middle
Alimentary (food) - middle is similar to rest of tract
Mucous - less hyperechoic than fluid - how would normally appear in a fasted animal

Question 4

How are the canine and feline stomachs different?

Answer 4

Dog - boomerang shape pancreas, long axis of the stomach is perpendicular to the spine
Cats - stomach is more angular. Pyloric antrum on the midline. Left pancreatic limb much larger than the right

Question 5

How can you differentiate different gastric wall diseases?

Answer 5

Thickening can occur with neoplasia or inflammaroty dieases (with or without loss of layering)
Anything over 10mm likely to be neoplastic
Ulcers can appear mass like and lymphoma can present as preserved layering just thickened, so always biopsy

Question 6

What are the common gastric neoplasias?

Answer 6

Cats - lymphosarcomas
Dogs - adenocarcinomas
Leiomyomas may be incidental findings

Question 7

How may gastic ulcers appear on U/S?

Answer 7

Normally in pyloric region
Focal gastric thickening
Often combined with loss of normal layering
may be able to see a crater and hyperechoic foci (gas)

Question 8

Where can you identify the descending duodenum

Answer 8

Most dorsal loop with a straight course in the right cranial abdomen

Question 9

How may peristalsis change with intestinal disaese

Answer 9

Movement normally reduced with obstructions/ periotonitis, although you can see temporary increases.

Question 10

How may linear FBs appear on US?

Answer 10

Plication of the intestines

Question 11

How do intususscpetions appear on US?

Answer 11

Multilayered appearance of the intestines
Normally at the ileocolic junction but can be anywhere
May lose wall layers due to oedema
Entrapped mesenteric fat can appear hyperechoic alongside the intususcepted segment
Can crudely assess for viability with doppler

Question 12

How do inflammatory conditions normally appear in the intestines?

Answer 12

Mild to moderate thickening of the small intestines
Mainly involving the mucosa/ submucosa
May appear normal

Question 13

What does corrugation of the intestinal walls suggest?

Answer 13

Pancreatits
Severe intestinal inflammation
Peritonitis
Infiltrative neoplasia

Question 14

How can lymphangiectasia appear?

Answer 14

Hyperechoic mucosal striations

snow storm appearance

Question 15

What do lymph nodes look like?

Answer 15

Slightly hypoechoic or isoechoic to the mesentry

Question 16

How may peritonitis look?

Answer 16

Mesentry becomes more hyperechoic
Loses its granular texture and becomes uniform
Other organs hard to see clearly
FF

Question 17

Where can you find the left and right limbs of the pancreas?

Answer 17

Right - with proximal duodenum
Left - Between the greater curvature of stomach cranially, colon caudally, splenic vein dorsally
May be able to see pancreatic ducts in cats

Question 18

How would the pancreas look with pancreatitis?

Answer 18

Acute pancreatitis - thickened, hypoechoic, surrounding mesentry hyperechoiccorrugated appearance of the duodenum
Chronic - can be minimal changes, may be heterogenous with areas of increased echogenicity due to fibrosis/ mineralisation

Question 19

What radiographic signs of small intestinal obstruction are there?

Answer 19

Plication of the intestines
Segmental dilation of the intestine with SI:height of L5 >2.07 = 90% chance of obstruction
Abnormal appearance or location of the bowel
Focal accumulation of granular tissue in the small intestine
Visible FB
Mottle gas appearance should raise suspicion, esp for a textile FB

Question 20

What ultrasonographic signs of small intestinal obstruction are there?

Answer 20

GI dilation - particularly likely if there is jejunal dilation with normal wall
Abnormal motility
Changes in wall thickness
FF
Hyperechoic structure with distal acoustic shadowing

Question 21

How useful is U/S in diagnosing gastric neoplasia

Answer 21

Some can be missed! - Should do endoscopy too if NAD
Gas and food can create artefact, but an empty stomach can make the wall look thicker than it is
Lymphoma is the most commonly missed gastric neoplasia on U/S

Question 22

Where does liquid and gas go on lateral radiographs and how can that help image the stomach?

Answer 22

Gas - on the non-dependent side (upper)
Liquid - on the dependent side (lower)
Pylorus is on L side of abdomen so with gas is visible on a R lateral
Fundus is on the R side of the abdomen

Question 23

What does gas within the liver normally suggest?

Answer 23

Hepatic abscess, but can be other things

Question 24

How should the liver appear on radiography?

Answer 24

Most cranial abdominal organ
Should be all or very nearly all within the costal arch
Caudal margins should be sharp
The gastric axis should be within a line parallel to the ribs and perpendicular to the spine - if not this suggest micro or macrohepatica

Question 25

How may biliary tract obstruction appear on US?

N.B if an animal has had prev biliary duct obstruction, dilation may remain even if the disease is resolved

Answer 25

Can’t use GB size as too variable
Common bile duct should be <3mm in dogs or <4mm in cats normally, greater = dilation
May se obstructing material along the duct
May see dilation of intrahepatic bile ducts if the obstruction is chronic (5-7d)

Question 26

How would you demonstrate biliary tract obstruction on rads?

Answer 26

Percutaneous u/s guided cholecystography

Question 27

What does a GB mucocoele look like on US?

Answer 27

GB distension wiht usually immobile contents
Kiwi/ stellate appearance
Mixed echogenicity

Question 28

What are possible consequences of a GB mucocoele?

Answer 28

Rupture and bile periotonitis

Biliary obstruction

Question 29

How would you look for a gastric ulcer on xray?

Answer 29

Gastrogram or double contrast gastrogram

US better

Question 30

How can intussusceptions appear on radiographs?

Answer 30

Intraluminal soft tissue opacity with crescentic linear gas delineating borders

Question 31

What normal structure can resemble an intusussception

Another similar problem would be caecal inversion

Answer 31

Ileocaecocolic junction

Not quite the same and also a lot smaller but beware

Question 32

When would you get pneumoperitoneum?

Answer 32

Rupture of a hollow viscous
Peritonitis (some types of e.coli produce gas)
Penetrating trauma

Question 33

Which LNs will enlarge with peritonitis?

Answer 33

Sternal

Question 34

Which vessel goes through the R limb of the pancreas?

Answer 34

The pacreatic duodenal vein

Question 35

How could you see pancreatitis on xray?

Answer 35

Often absent
May see mass effect (distance between the stomach and colon increased)
Focal poor serosal detail