Imaging of the GI tract Flashcards
What is a ring down artefact?
Hyperechoic band distal to a a shadowing structure
Caused by exciting liquid trapped between gas bubbles
What type of trasducer should be used for the GI tract?
High frequency (7.5-10) May need lower for big dogs and deeper structures
What are the patterns that can be produced by luminal contents?
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
How are the canine and feline stomachs different?
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
How can you differentiate different gastric wall diseases?
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
What are the common gastric neoplasias?
Cats - lymphosarcomas
Dogs - adenocarcinomas
Leiomyomas may be incidental findings
How may gastic ulcers appear on U/S?
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)
Where can you identify the descending duodenum
Most dorsal loop with a straight course in the right cranial abdomen
How may peristalsis change with intestinal disaese
Movement normally reduced with obstructions/ periotonitis, although you can see temporary increases.
How may linear FBs appear on US?
Plication of the intestines
How do intususscpetions appear on US?
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
How do inflammatory conditions normally appear in the intestines?
Mild to moderate thickening of the small intestines
Mainly involving the mucosa/ submucosa
May appear normal
What does corrugation of the intestinal walls suggest?
Pancreatits
Severe intestinal inflammation
Peritonitis
Infiltrative neoplasia
How can lymphangiectasia appear?
Hyperechoic mucosal striations
snow storm appearance
What do lymph nodes look like?
Slightly hypoechoic or isoechoic to the mesentry
How may peritonitis look?
Mesentry becomes more hyperechoic
Loses its granular texture and becomes uniform
Other organs hard to see clearly
FF
Where can you find the left and right limbs of the pancreas?
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
How would the pancreas look with pancreatitis?
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
What radiographic signs of small intestinal obstruction are there?
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
What ultrasonographic signs of small intestinal obstruction are there?
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
How useful is U/S in diagnosing gastric neoplasia
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
Where does liquid and gas go on lateral radiographs and how can that help image the stomach?
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
What does gas within the liver normally suggest?
Hepatic abscess, but can be other things
How should the liver appear on radiography?
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
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
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)
How would you demonstrate biliary tract obstruction on rads?
Percutaneous u/s guided cholecystography
What does a GB mucocoele look like on US?
GB distension wiht usually immobile contents
Kiwi/ stellate appearance
Mixed echogenicity
What are possible consequences of a GB mucocoele?
Rupture and bile periotonitis
Biliary obstruction
How would you look for a gastric ulcer on xray?
Gastrogram or double contrast gastrogram
US better
How can intussusceptions appear on radiographs?
Intraluminal soft tissue opacity with crescentic linear gas delineating borders
What normal structure can resemble an intusussception
Another similar problem would be caecal inversion
Ileocaecocolic junction
Not quite the same and also a lot smaller but beware
When would you get pneumoperitoneum?
Rupture of a hollow viscous
Peritonitis (some types of e.coli produce gas)
Penetrating trauma
Which LNs will enlarge with peritonitis?
Sternal
Which vessel goes through the R limb of the pancreas?
The pacreatic duodenal vein
How could you see pancreatitis on xray?
Often absent
May see mass effect (distance between the stomach and colon increased)
Focal poor serosal detail
