Small Bowel Imaging Flashcards
which is the best modality for SB imaging in the acute setting and why - 5 points
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
what are symptoms of SBO - 2 points
what is the first port of call
what are the most common causes of SBO - 4 points
pain
vomiting
X-RAY
adhesions, secondary to intra-abdominal surgery, hernias, tumours, Crohn’s Disease
what is seen on an x-ray showing SBO - 3 points
SB > 3cm
dilated to transition point
collapsed bowel loops from this point
what is post-operative ileus
what can intra-abdominal inflammation lead to?
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’
describe gastrografin small bowel follow through - 5 points
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
preparation for CT abdo in acute setting - 7 points
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
why gastrografin for CT abdo
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
when is a small bowel follow through used
what is used to investigate
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
clinical indications for SB imaging - 8 points
?crohn's ?adhesions IBD intermittent partial small bowel obstruction delineate anatomy for surgery transit time unexplained GI bleeding ?small bowel fistulae
what are the symptoms for SI imaging - 7 points
unexplained abdo pain diarrhoea vomiting bloating unexplained weight loss anaemia malabsorption
what are the advantages of a small bowel follow through - 5 points
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
barium sulphate used in small bowel follow through - 5 points
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
preparation for small bowel follow through - 5 points
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
patient preparation for small bowel follow through- 7 points
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
contraindications for small bowel follow through
known or suspected perforation myasthenia gravis megacolon (loss of peristalsis) severe constipation bowel obstruction high risk of aspiration pregnancy
procedure for small bowel follow through - 5 points
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
side effects for small bowel barium follow through
what advice is given to the patient
white/pale stools for the next few days
abdominal cramp
constipation
drink extra fluids to help clear the barium out
what is enterography - 2 points
where the bowel is filled by ingesting large amounts of fluids orally
- doesn’t distend the bowel effectively but patients dislike NJ tube
what is enterocylsis - 3 points
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
what are important features for a good contrast agent - 2 points
high contrast resolution between the bowel wall and the small bowel lumen
homogenous signal intensity of the lumen
why are biphasic oral contrast agents used in MR enterography - 2 points
what are some examples - 3 points
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
why are Klean Prep and Mannitol optimal oral contrast agents
what should the patient be warned having taken this
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
what are the advantages of using water as an oral contrast agent - 3 points
cheap
well tolerated
safe alternative
what are the disadvantages of using water as an oral contrast agent - 2 points
rapidly absorbed - often doesn’t reach terminal ileum and the small bowel is therefore under-distended
Describe Klean Prep
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
what are the side effects of Klean Prep
what can be given as an alternative
diarrhoea
nausea
abdominal pain
bloating
water or mannitol
patient preparation for MR enterography - 7 points
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)
contraindications for MR enterography - 7 points
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
what are the side effects of buscopan
when should an alternative be given and what is the alternative
blurred vision
dry mouth
tachycardia
if the patient has glaucoma or tachycardia then glucagon is offered
procedure of MR enterography - 6 points
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
procedure of MR enterography once given contrast - 4 points
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
Procedure for CT enterography - 8 points
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
which test for ?crohn’s
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
which test for confirmed crohn’s
<40yrs MRE
>40yrs CTE as 1st investigation then MRE
Mapping for surgery = barium follow through
judge SBFT - 5 points
functional study widely available uses radiation most patients tolerate barium fairly easily - due to less volume jejunal loops imaged
judge MRE - 5 points
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
judge CTE - 5 points
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
