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Y4 SA - Internal medicine > Imaging of gastrointestinal disease > Flashcards

Imaging of gastrointestinal disease Flashcards

1
Q

Describe how the normal pancreas appears on radiography, where is it located?

A
  • Normal pancreas is not observed on plain radiographs
  • Medial to duodenum, between gastric body and transverse colon, medial to spleen and cranial to left kidney
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2
Q

Which imaging modality is best for visualisation of the pancreas?

A

Ultrasound

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3
Q

Describe pancreatic enlargement and how it appears on radiography

A
  • Pancreatitis or neoplasia
  • Mass effect: Lateral displacement of the duodenum and caudal displacement of the transverse colon
  • Increased ST opacity in the craniodorsal to mid abdomen caudal to fundus
  • Localized loss of serosal detail (focal fluid/peritonitis)
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4
Q

Describe the normal oesophagus on radiography

A
  • On a plain radiograph not clearly delineated unless gas filled.
  • Midline structure within the mediastinum
  • A small amount of gaseous dilation is normal (sedation related).
  • Fluoroscopy essential
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5
Q

Describe a megaoesophagus and how it presents on radiography

A
  • Segmental or generalised dilation
  • May cause ventral deviation of the trachea and widening of the mediastinum.
  • Tracheo-oesophageal stripe sign
    (summation of tracheal wall and oesophageal wall).
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6
Q

Where are the predilection sites for an oesophageal foreign body?

A

Thoracic inlet
Heart base
Cranial to the diaphragm/cardia

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7
Q

Which contrast media is contraindicated with suspected oesophageal perforation? Which can be used?

A

Barium
Use endoscopy or non-ionic, iodine containing contrast

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8
Q

Where would gas/material leak if the (thoracic) oesophagus was perforated?

A

Mediastinum – seen on the D/V view

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9
Q

Where does gas move within a hollow viscus (e.g. stomach, intestine, etc)?

A

Non-dependent side

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10
Q

How is positional radiography used in gas distribution?

A

Right and left lateral view and VD ± DV

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11
Q

Where do we expect the gas within the stomach based on the radiographic view?

A

Right lateral view: Fundus.
Left lateral view: Body/pyloric antrum.
Ventrodorsal view: Body (superimposed over the vertebral column).
Dorsoventral view: Fundus (left cranial quadrant).

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12
Q

Why are contrast studies less used now?

A

Time consuming, cost intensive and low diagnostic yield
Superseded by combining radiography with ultrasound instead
They are only useful, if carried out properly

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13
Q

Where does the normal stomach lie

A

Positioned within the costal arch in the cranial abdomen, directly caudal to the liver.

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14
Q

Name the compartments of the stomach

A

Cardia
Fundus
Body
Pyloric antrum/pylorus

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15
Q

Do not mistake a fluid filled pyloric antrum with..?

A

A mass

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16
Q

Name the 5 layers of the stomach from the outside in

A

Serosa
Muscularis
Submucosa
Mucosa
Lumen

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17
Q

Which layers of the stomach are hyperechoic (dark)?

A

Muscularis and mucosa

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18
Q

Rugal folds are visible in which parts of the stomach

A

Fundus
Body

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19
Q

Describe how gastric dilation presents on radiography

A

Gas opacity in fundus/body: very “dark” = large volume of gas

20
Q

What are the two causes of fluid and gas dilation of the stomach

A

Pyloric outflow obstruction
Function ileus

21
Q

What are the two causes of just gas dilation of the stomach

A

Aerophagia
GD/GDV

22
Q

How does a fluid and gas dilation of the stomach present on radiography?

A

Mostly soft tissue opacity with a faint gas opacity “bubble” floating on top

23
Q

How are stomach foreign bodies assessed on radiography

A
  • Easy to identify if of mineral/metallic opacity.
  • Remember orthogonal views are necessary to confirm location.
  • Gas may be trapped in textile or botanical FB or toys resulting is bizarre gas patterns.
  • May cause partial or complete obstruction
24
Q

What is gastric dilation and volvulus?

A

Life threatening disease!
Marked gas dilation and rotation around the longitudinal axis

25
Q

Describe how the stomach rotates in GDV

A
  • Pylorus shifts dorsally, cranially, and to the left
  • Body shifts toward the right
  • Fundus usually is displaced ventrally and to the right
  • Spleen follows the greater curvature toward the right (gastrosplenic ligament)
26
Q

How does GDV present on radiography?

A
  • Marked gas dilation and displacement of gastric compartments
  • Fundus displaced caudoventrally and right.
  • Pyloric antrum displaced craniodorsal and left.
  • Compartmentalisation with a dividing soft tissue band (“shelf”).
  • Mass effect on other abdominal organs
27
Q

Describe the normal radiographic appearance of the SI

A
  • Normally soft tissue opacity band/tube or as circular/ovoid ST opacity when viewed end-on
  • Some homogeneous gas-filling is normal in dogs
  • Little to no gas filling in cats
28
Q

Describe the ‘wall thickness illusion’ of the small intestine

A
  • Wall thickness cannot be reliably assessed on plain radiographs
  • “Wall” is summation of true wall and intestinal luminal fluid
  • Fluid and soft tissue indistinguishable on radiographs
  • Requires contrast (to mix with fluid) or ultrasonography
  • Not much fluid, approximates wall thickness
29
Q

Which layer of the small intestine is the thickest?

A

Submucosa

30
Q

Which area of the small intestine has the thickest wall?

A

Duodenum

31
Q

Which layer of the small intestine is thicker in the ileum? How does this appear on US?

A

The submucosa is thicker in the ileum and flower-like/wheel-like appearance on transverse images

32
Q

List the causes of small intestinal dilation

A

Mechanical obstruction:
- Foreign body
- Tumour
Functional ileus:
- Severe inflammation
- Toxic
- Stress

33
Q

Define ileus

A

Failure of the intestinal contents to pass normally
Can be fluid or gas dilation

34
Q

No one loop of small intestine should be more than … the diameter of any other loops

A

2X

35
Q

Describe how an obstruction in the small intestine leads to an obstructive pattern seen on radiography

A
  • Fluid and/or gas dilation proximal to the obstruction.
  • Creates “two populations of intestine” around the obstruction
    -> one abnormal proximal
    -> one normal distal population to obstruction
    May not see two population if the obstruction is very proximal or very distal!
36
Q

Once a FB makes it passed which point of the GIT do you not longer have to worry about it?

A

Colon

37
Q

Describe how a small intestinal obstruction presents on ultrasound

A

Secondary changes depending on level of obstruction:
- Fluid dilation proximal to FB and to-and-fro movement
- Normal intestines distal to the obstruction (two populations)

38
Q

How does a small intestinal FB present on ultrasound?

A

Hyperechoic, irregular or artificially symmetrical shape
Usually strong distal shadowing

39
Q

Describe linear foreign bodies and the effect they have on the GIT

A

Commonly seen in cats
Plication/hair-pin bends, bunching
Cause telescoping of the SI onto the FB
+/- localised peritonitis (loss of serosal detail, streaky appearance

40
Q

Describe intussusception and how it appears on radiography

A

Most commonly in young dogs and cats, in older patients usually secondary to other pathology
- Ovoid/elongated ST mass/dilation
- Possibly crescent shaped gas opacity between intussusceptum (inner) and intussuscipiens (outer)
- No “normal” caecal gas, shortened colon (ileocolic int.)

41
Q

Describe how intussusception appears on ultrasound

A
  • Easily diagnosed on ultrasound
  • Onion ring/bullseye appearance on transverse images
  • Intestinal walls identified within intestinal lumen
  • Also vessels/blood flow within the lumen
42
Q

How is small intestinal neoplasia diagnosed using imaging

A
  • Difficult to identify, need to be of substantial size
  • Signs secondary to obstruction may be seen
  • Care not to overinterpret “apparent wall thickening”
  • Localised masses, irregular gas filling/contrast column
  • US very useful
43
Q

How would a small intestinal neoplasia appear on ultrasound?

A

Loss of wall layering
May have central gas containing lumen (distal shadowing)
May see signs of obstruction

44
Q

Where is the caecum located normally?

A

In right dorsal aspect of abdominal cavity, often level of the left kidney (on a lateral radiograph)

45
Q

How does the normal caecum appear on radiography?

A
  • In cats is small, rarely contains gas and normally not visible or comma shaped
  • In dogs appears as a semicircular, snail-shell gas filled structure
46
Q

The colon is divided into which 3 sections?

A

Ascending, transverse, and descending colon

Y4 SA - Internal medicine (7 decks)

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