Intro of CT of Abdo Flashcards
what are general considerations for Abdo CT - 8 points
ID LMP patient prep - oral contrast, bowel clearance positioning scan parameters contrast media other drugs post procedure care
patient preparation for CT Abdo
cannulations - rule out contraindications first
check they’ve followed prep instructions - have they taken picolax? has it worked?
oral contrast/water
explanation
why are oral contrast agents used
to distinguish anatomy and pathology in the GIT - used for most CT ado and pelvic exams unless no suspicion of bowel pathology or when administration would delay a diagnosis in a trauma setting
what would minimise the risk of aspiration
use of naso-gastric tube to administer oral contrast
what is the patient prep for CT Abdo - 5 points
DILUTE gastrografin - +ve agent, approx 8mls GG in 250mls water
24hr prep - allow time to reach rectum
4 x doses 24hrs, 10pm day prior, 9am on day and immediately before
1/2 prep = upper abdo only - 2 x doses - 30 mins and immediately prior
TIME CONSUMING TO ADMINISTER
what else is used in patient prep for CT Abdo
WATER - -ve agent, immediately before scan to distend stomach for better visualisation and to better visualise stomach/bowel wall
quick and easy, cheap, patient friendly
when should oral contrast not be given
suspected bowel obstruction - usually air and fluid within the bowel to provide negative contrast h/e with known obstruction = administrated to assess transit through site of obstruction
acute gastrointestinal bleeding/bowel ischaemia - oral contrast in bowel lumen with obscure intraluminal bleeding and subtle abnormalities in bowel wall enhancement
suspected bowel perforation - contrast would leak out of bowel and cause infection
patient preparation for rectal contrast media
when should it not be given
diluted gastrografin
diluted iodinated contrast
gas - O2 or CO2
in patients with recent colonic or rectal surgery
what additional patient prep is required for CTC
Picolax and low residue diet - 48 hours, - to clear bowel of faecal residue
what additional patient prep is required for CT IVU
hydration of patient prior to exam to improve distention of urinary tract and provide optimal visualisation of the kidneys
why can patient positioning be varied between prone and supine - 2 points
to remove overlying fluid or faeces which may mimic or obscure pathology
to see if renal stones move
why scan on arrested respiration
to reduce movement artefact
describe iv contrast media
helps identify blood vessels, anatomy, pathology
give 3 examples of iv contrast media
niopam, omnipaque, visipaque
contraindications for iv contrast media
renal compromise
diabetes
any previous adverse reactions
asthma/hayfever
what is a Hickman’s line
an intravenous catheter most often used for the administration of chemotherapy or other meds as well as withdrawal for bloods
some types used mainly for he purpose of dialysis
may remain in place for extended periods and used when LT IV access needed
describe creatinine - 4 points
product of the breakdown of creatinine phosphate within the muscles
filtered by the kidneys
if any renal compromise then creatinine rises and hence is a measure of kidney function
> 150 then consult radiologist prior to proceeding
Describe eGFR
estimated glomerular filtration rate based on creatinine level, age, sex, race < 30 = involve renal team 30-60 = ask radiologist > 60 = normal
what is the purpose of contrast-enhanced CT
to find pathology by enhancing the contrast between a lesion and the normal surrounding structures
what phases are commonly used for CT Abdo
unenhanced
arterial
portal venous
late/early arterial and late/early venous can also be used to identify particular pathologies
describe the arterial phase of a CT Abdo
optimal enhancement occurs between 5-15s following IV injection
arteries visualised during early arterial phase
useful for looking for arterial abnormalities - e.g. aortic aneurysms or dissection
describe the portal venous phase of a CT Abdo
optimal at approx 40/50 seconds after injection of IV contrast
the liver parenchyma enhances
excellent for visualising all abdominal organs
liver mets will be visualised in this phase
describe contrast media timing
can be tailored to suit each patient
allows for real time visualisation of the contrast within a particular vessel/structure
delayed scans can be useful in assessing function - CT IVU = rate/amount of excretion of contrast from kidney
which procedures require administration of particular drugs and what are they
CT IVU - Frusemide (diuretic - induces urination)
CT colonography - Buscopan (muscle relaxant)
post procedure care for CT Abdo
Cannula removal
hydration - following iv contrast
results
