Small Bowel Imaging

Question 1

which is the best modality for SB imaging in the acute setting and why - 5 points

Answer 1

CT
readily available
quick acquisition
relatively low cost
positive (gastrografin) or negative (water/Klean prep) oral contrast used where poss - positive = useful w people with low BMI
MR in the critically ill patient = much more difficult bc of requirements of MR-compatible monitoring and anaesthesia equipment and reduced accessibility to patient leading to difficulties with airway management, intravenous access, patient visualisation as well as increased procedure duration

Question 2

what are symptoms of SBO - 2 points

what is the first port of call
what are the most common causes of SBO - 4 points

Answer 2

pain
vomiting
X-RAY
adhesions, secondary to intra-abdominal surgery, hernias, tumours, Crohn’s Disease

Question 3

what is seen on an x-ray showing SBO - 3 points

Answer 3

SB > 3cm
dilated to transition point
collapsed bowel loops from this point

Question 4

what is post-operative ileus

what can intra-abdominal inflammation lead to?

Answer 4

term used for aperistaltic bowel not caused by mechanical obstruction - common after abdominal surgery, radiological feature similar to obstruction

localised ileus - appear as a single loop of dilated bowel known as ‘sentinel loop’

Question 5

describe gastrografin small bowel follow through - 5 points

Answer 5

for patients with SBO caused by adhesions
should already be NBM
100ml gastrografin given orally or via NGT (clamped 1hr post administration)
x-ray taken at 6hrs - if through to caecum - finished
if not another at 24hrs - if still not through = surgery to relieve obstruction

Question 6

preparation for CT abdo in acute setting - 7 points

Answer 6

starve 4hrs prior
10ml of gastrografin in 500ml water 2hrs prior
cannula inserted
LMP
scan at 75s post iv contrast
if patient unable to tolerate gastrografin = scan w/o oral contrast
if chance of GI bleed = no gastrografin

Question 7

why gastrografin for CT abdo

Answer 7

radiopaque due to iodine content (370mg/ml)
use by oral/rectal administration only
non-toxic
if perforation present = absorbed by abdominal cavity and excreted by kidneys
can have allergic reaction but v rare and can usually still give to patients with previous iv contrast reaction

Question 8

when is a small bowel follow through used

what is used to investigate

Answer 8

most commonly in the UK in patients with chronic or subacute symptoms
CT and MRI = most commonly used modalities - availability and widely accepted however SBFT still readily used

Question 9

clinical indications for SB imaging - 8 points

Answer 9

?crohn's
?adhesions
IBD
intermittent partial small bowel obstruction
delineate anatomy for surgery 
transit time
unexplained GI bleeding
?small bowel fistulae

Question 10

what are the symptoms for SI imaging - 7 points

Answer 10

unexplained abdo pain
diarrhoea
vomiting
bloating
unexplained weight loss
anaemia
malabsorption

Question 11

what are the advantages of a small bowel follow through - 5 points

Answer 11

if well performed then its sensitive tool for early diagnosis of crohn’s, ulcers, due to high spatial resolution

functional study - useful to demonstrate reduction/loss of motility as a marker of disease motility

good for mapping of strictures prior to surgery

less radiation dose than CTE

often better toleration of barium and its side effects than other agents used for CTE and MRE

Question 12

barium sulphate used in small bowel follow through - 5 points

Answer 12

E-Z-Paque - 96% with powder for oral/rectal suspension mixed with cold water to approx 50%
radio-opaque
if goes outside GI tract = severe inflammation
if patient aspirates = can induce severe pneumonia
can become hard and inspissated causing intestinal obstruction

Question 13

preparation for small bowel follow through - 5 points

Answer 13

add water to 2.5cm above barium level
secure lid and shake vigorously
add more water to top of container (approx 50%)
replace lid and shake for 30s
always re-shaek just before patient drinks it

Question 14

patient preparation for small bowel follow through- 7 points

Answer 14

from 1pm day before, nothing to eat but plenty of fluids
from 11pm NBM
check patient ID and clinical history
LMP
explanation of procedure and check for contraindications
10mls of Domperidone given 10mins before barium
patient into gown and artefacts removed

Question 15

contraindications for small bowel follow through

Answer 15

known or suspected perforation
myasthenia gravis
megacolon (loss of peristalsis)
severe constipation
bowel obstruction
high risk of aspiration
pregnancy

Question 16

procedure for small bowel follow through - 5 points

Answer 16

10mls Domperidone given - increases the transit through the stomach (increase in gastrointestinal peristalsis) and relieves nausea and vomiting
Barium given 10 mins later - drink at regular rate, not to sip it
Prone x-rays taken at 10min and 20min - prone to allow abdominal pressure to separate bowel loops - 10min must be done so as not to miss early pathology even if patient has not finished drinking
Radiologist reviews 40mins 80mins 120mins etc.
Radiologist screens once barium reaches caecum
terminal ileum imaged using fluoroscopy

Question 17

side effects for small bowel barium follow through

what advice is given to the patient

Answer 17

white/pale stools for the next few days
abdominal cramp
constipation

drink extra fluids to help clear the barium out

Question 18

what is enterography - 2 points

Answer 18

where the bowel is filled by ingesting large amounts of fluids orally
- doesn’t distend the bowel effectively but patients dislike NJ tube

Question 19

what is enterocylsis - 3 points

Answer 19

direct infusion of fluid into the small bowel after placement of a naso-jejunal tube

• requires fluoroscopic guidance for insertion to ensure placement
• provides functional information about the bowel

Question 20

what are important features for a good contrast agent - 2 points

Answer 20

high contrast resolution between the bowel wall and the small bowel lumen
homogenous signal intensity of the lumen

Question 21

why are biphasic oral contrast agents used in MR enterography - 2 points

what are some examples - 3 points

Answer 21

low signal intensity on T1 weighted images and high signal intensity on T2 weighted images
one T1 weighted images post iv contrast, the contrast between the enhancing bowel wall and dark lumen is optimised

Klean Prep, Mannitol, Water

Question 22

why are Klean Prep and Mannitol optimal oral contrast agents

what should the patient be warned having taken this

Answer 22

hyperosmolar
distend the small bowel by retaining the water it is taken with in the bowel instead of being absorbed across the intestinal mucosa

diarrhoea within an hour

Question 23

what are the advantages of using water as an oral contrast agent - 3 points

Answer 23

cheap
well tolerated
safe alternative

Question 24

what are the disadvantages of using water as an oral contrast agent - 2 points

Answer 24

rapidly absorbed - often doesn’t reach terminal ileum and the small bowel is therefore under-distended

Question 25

Describe Klean Prep

Answer 25

69g sachet mixed with a litre of water
osmotic laxative
distends the small bowel as it retains the water it is taken with in the bowel instead of absorbing

Question 26

what are the side effects of Klean Prep

what can be given as an alternative

Answer 26

diarrhoea
nausea
abdominal pain
bloating

water or mannitol

Question 27

patient preparation for MR enterography - 7 points

Answer 27

nothing eat from 5pm day before, drinking plenty of fluids
NBM 11pm day before
patient asked to remove jewellery and any other metal and change into gown
safety form completed
ask patient if they have a stoma - if yes, scan supine
cannula inserted - check for contraindications for contrast or buscopan
patient asked to drink up to 1.5 litres of Klean Prep within 45mins (or alt contrast if necessary)

Question 28

contraindications for MR enterography - 7 points

Answer 28

pacemaker
recent surgery - last 4-6 weeks
metallic foreign body within orbit
brain aneurysm clips
metallic heart valves - require manufacturer and model details 
cochlear implants 

patient must be willing to lie very flat and perform multiple breath holds

Question 29

what are the side effects of buscopan

when should an alternative be given and what is the alternative

Answer 29

blurred vision
dry mouth
tachycardia

if the patient has glaucoma or tachycardia then glucagon is offered

Question 30

procedure of MR enterography - 6 points

Answer 30

1.5T scanner with 16 channel phased array coil
patient empties bladder before scan
drinks last cup immediately before getting on table (helps fill jejunal loops)
positioned positioned feet first and prone (unless stoma) - helps separate bowel loops and reduce movement artefact and safer if patient vomits
perform survey and reference scans
perform coronal BFFE and check all small bowel filled up to hepatic flexure of colon ideally
NOT = off table and drink more
YES = continue with scans

Question 31

procedure of MR enterography once given contrast - 4 points

Answer 31

give contrast for detection of active inflammation
scan after 60s post contrast
to prevent blurring from peristalsis buscopan given immediately prior to scans
AREAS OF CONTRAST APPEAR DARK
if stoma - Klean Prep should be seen in stoma

Question 32

Procedure for CT enterography - 8 points

Answer 32

nothing to eat from 5pm day before but drink plenty of fluid
NBM from 11pm
LMP
10ml Domperidone 
1.5 litres Klean Prep in 45mins 
IV cannula inserted
20mg Buscopan 
scan at 50s post iv contrast = enteric phase 
same aftercare as MR

Question 33

which test for ?crohn’s

Answer 33

all patients should have colonoscopy with terminal ileum biopsy where possible
Normal Terminal Ileum = Video Capsule Endoscopy
Terminal Ileum Not Seen = Patency Capsule & Video Capsule Endoscopy
Abnormal Terminal Ileum/Obstructive Symptoms = CTE

Question 34

which test for confirmed crohn’s

Answer 34

<40yrs MRE
>40yrs CTE as 1st investigation then MRE
Mapping for surgery = barium follow through

Question 35

judge SBFT - 5 points

Answer 35

functional study 
widely available 
uses radiation
most patients tolerate barium fairly easily - due to less volume 
jejunal loops imaged

Question 36

judge MRE - 5 points

Answer 36

detailed extra-mural information - e.g. abscesses
patients can struggle with Klean Prep due to quantity, taste and after-effects
difficult to distend jejunum
limited scanner availability
no radiation but lots of other contraindications

Question 37

judge CTE - 5 points

Answer 37

detailed extra-mural information
patients can struggle with Klean Prep due to quantity, taste and after-effects
difficult to distend jejunum
high radiation dose
shorter scan times