Imaging GI tract

Question 1

How can bowel perforation be identified?

Answer 1

Erect chest x-ray. It will show free gas under the diaphragm

Question 2

When are x-rays used for abdomen?

Answer 2

Using less and less now, more likely to use CT as they are more specific and detailed

But can see dilation/obstruction of bowel or calcification of pancreas/vessels/renal canaliculi on x-ray
Or even flare ups of IBD
Foreign bodies

Question 3

Way to interpret abdo x-ray

Answer 3

ABDO X
Air - should only be in lumen of bowel, not anywhere else. Could suggest pneumoperitoneum
Bowel - dilated? thickening?
Dense structures and calcification - bones and stones
Organs and soft tissues
X - eXternal objects, lines tubes etc

Question 4

How to differentiate small bowel vs large bowel?

Answer 4

Small bowel: central, vavlulae conniventes (plicae circularis) are full thickness, contains air or fluid

Large bowel: peripheral, haustral folds only extend partially across and more spaced out, contains air or faeces

Question 5

Dilation of bowel measurements

Answer 5

If small bowel >3cm
If large bowel >6cm
If caecum >9cm
= dilation
369 rule

Question 6

X-ray sign of colitis?

Answer 6

Thumb printing - shows thick oedematous folds

Question 7

Sigmoid volvulus vs caecal volvulus

Answer 7

Caecal will be in abnormal position if it has twisted and is due to congenital condition allowing the twisting

Sigmoid volvulus - caecum will be in normal place, due to slow bowel and constipation causing stretching of sigmoid on mesentery

Question 8

Radiological sign for sigmoid volvulus

Answer 8

Coffee bean sign - pointing from left iliac fossa to right upper quadrant

Question 9

What is fluroscopy?

Answer 9

Barium swallow usually used
Can then create video watching dye pass down upper GI tract

Question 10

What can fluroscopy be used to visualise?

Answer 10

Oesophageal carcinoma - showing stricture of oesophagus, dye does not flow well through it

ERCP (Endoscopic retrograde cholangiopancreatography) - inject dye into ampulla of vater using upper GI endoscopy
Dye goes into common bile duct etc and can identify gallstones/obstruction
Can then drag and remove obstruction, insert plastic stent or widen ampulla using small cut

Achalasia - LOS denervation, spasms making flow into stomach slow and food builds up in oesophagus

Question 11

When is ultrasound used?

Answer 11

If cannot have radiation - eg pregnant
Widely available and good for soft tissues of abdomen and blood vessels esp for gall bladder/biliary tree

NOT good for gas filled structrues eg lungs, just get shadows

Question 12

Problem with ultrasound

Answer 12

User dependent

Question 13

What can you visualise in ultrasound?

Answer 13

Layers of bowel, mucosa, peristalsis, gall bladder stones/duct dilation

Question 14

What is another version of ultrasound?

Answer 14

Doppler - allows motion and calculations of flow through vessels etc
Works by sound wave signal changes as things go further away or closer

Question 15

When is CT used for abdo?

Answer 15

GOLD STANDARD - if acute GI presentation or GI cancer

Question 16

Contrast used in CT why?

Answer 16

Contains iodine, makes structures appear bright on x-ray and enhances image
Usually administered via ant cubital fossa

Question 17

Different stages of contrast

Answer 17

Inject contrast then:
At 30 seconds - arterial system is highlighted well
If another 30 seconds (1 minute passed) organs and GI tract are illuminated well
8-10 minutes - renal excretory phase - highlights collecting system of kidney

Question 18

MRI why?

Answer 18

No radiation, magnets
Assess soft tissues very well, can see motility of bowel

Question 19

What can you generate using CT?

Answer 19

3D images of scans and even generate virtual colonoscopy through bowel to find polyps etc

Question 20

When is angiography used for abdomen?

Answer 20

So you can see vessels, if suspect occlusion

Question 21

Describe angiography

Answer 21

Wire via femoral vessels to abdomen vessels
Inject contrast to illuminate vessels
If you can see a contrast blush - where it spreads out, shows there is a bleed
Can then inject coils to block vessels (small metal things)
Blood supply to gut isnt massively effected as good collateral supply

Question 22

Toxic megacolon appearance

Answer 22

Dilation colon
Pseudopolyps
Oedema

Question 23

Common GI contrast test (CT)

Answer 23

Swallow test which can highlight problems/anatomical variance with the stages of swallowing and a follow through which allows the contrast to pass into the small intestine

Question 24

What can be used contrast wise to visualise large bowel?

Answer 24

Contrast enema - up rectum

Question 25

MRI vs CT

Answer 25

MRI - better for soft tissues, bone not as detailed, no radiation, contraindications if have metal in body (magnetic fields), claustrophobia, longer - 30 mins uses: spinal cord, brain, ligaments, soft tissues, very noisy

CT - better for bone, radiation, shorter 5/10 mins, uses: trauma, cancer staging, blood vessel pathology