Session 10: Imaging of the Gastrointestinal Tract

Question 1

Imaging modalities of GI tract.

Answer 1

Abdominal x-ray

Erect chest x-ray

Barium swallow

Barium enem

Barium meal

Water soluble contrast

Ultrasound

CT

MRI

PET-CT

Angiography

Question 2

What gives the highest dose of radiation?

Answer 2

CT abdo/pelvis

Question 3

Risks of imaging of GI tract.

Answer 3

Carcinogenesis

Genetics

Developmental risks to foetus

Question 4

Why would an AXR be requested?

Answer 4

Acute abdominal pain

Small or large bowel obstruction

Acute exacerbation of IBD like flare-ups

Renal colic is now done by CT

Question 5

Systemic approach for an AXR.

Answer 5

ABDO X

Air/gas

Bowel

Dense structures (calcifications and bones)

Organs and soft tissue like liver, spleen and kidneys

eXternal objects and artifacts

Question 6

How will small bowel present on an AXR?

Answer 6

Central position and have lines (valvulae conniventes) that cross the entire bowel wall.

Question 7

How will large bowel present on an AXR?

Answer 7

Peripheral position and have incomplete lines (haustra).

Faeces can be visible due to the slow transit time of large bowel.

Question 8

Give examples of abnormal gas patterns to recognise.

Answer 8

Rules of 3s (3,6,9)

Small bowel obstruction (>3 cm)

Large bowel obstruction (>6 cm)

Competent ileocaecal valve (>9 cm)

Incompetent ileocaecal valve (<9 cm)

Paralytic ileus

Volvulus

Toxic megacolon

Question 9

Causes of small bowel obstrution.

Answer 9

Adhesions

Hernias

Tumours

Inflammation

Question 10

Causes of large bowel obstruction.

Answer 10

Colorectal carcinoma

Diverticular stricture

Hernia

Volvulus

Pseudo-obstruction

Question 11

How might sigmoid volvulus present on AXR?

Answer 11

Large coffee bean sign starting in the LIF and pointing towards RUQ.

Question 12

What is this?

Answer 12

Colonic dilation

Oedema

Pseduopolyps

Toxic megacolon

Question 13

What is this?

Answer 13

Called lead pipe colon where there is a featureless colon with the loss of haustra.

It is due to Ulcerative colitis

Question 14

Answer 14

Renal calculi

Question 15

Answer 15

Chronic pancreatitis

Question 16

Answer 16

Vascular calcification

Question 17

Answer 17

Abdominal aortic aneurysm

Question 18

Answer 18

Foreign bodies

Question 19

Why might an erect chest x-ray be ordered?

Answer 19

In case of bowel perforation

Question 20

Give causes of bowel perforation

Answer 20

Peptic ulcer

Diverticular

Tumour

Obstruction

Trauma

Iatrogenic

Question 21

How will bowel perforation show up on an erect chest x-ray?

Answer 21

It will show free gas right under the diaphragm.

Question 22

What is used to define hollow viscera?

Answer 22

Barium contrast and water soluble contrast.

Question 23

Give the common GI contrast studies.

Answer 23

Swallow

Meal

Follow through

Enema

Question 24

What does a swallow test show?

Answer 24

It can highlight problems and anatomical variances found with the stages of swallowing.

Question 25

What does a follow through show?

Answer 25

Allows contrast to pass into the small intestine and can show any variances or pathology in small intestines. Meal barium shows the stomach

Question 26

What does a contrast enema show?

Answer 26

Allows the large intestine to be highlighted

Question 27

Why might a CT be used?

Answer 27

To produce a high resolution image of the abdomen that can be further augmented with contrast to show any pathology not visible on x-ray. However it comes iwth a cost of high dose radiation.

Question 28

Answer 28

Question 29

Answer 29

Question 30

Answer 30

Question 31

Answer 31

Question 32

Answer 32

Question 33

What is virtual colonoscopy?

Answer 33

Individual images from a CT scan that can be reformatted and combined to produce a 3D representation of the scanned anatomy.

Question 34

Why might an MRI be used?

Answer 34

To give a detailed and high contrast image of the abdomen **without radiation**. It can be enhanced by contrast. It is however very time consuming.

Question 35

Why might abdominal USS be used?

Answer 35

Cheap and portable method. It is user dependant however and you might miss pathology.

Question 36

What is abdominal USS often used for?

Answer 36

To visualise the biliary tree to see gallstones and dilated bile ducts.

Question 37

Why are AXRs not used as much any more?

Answer 37

Because they are not very sensitive and not very specific. A lot of radiologist gets it wrong 30-40% of the time.