Intro of CT of Abdo

Question 1

what are general considerations for Abdo CT - 8 points

Answer 1

ID 
LMP
patient prep - oral contrast, bowel clearance 
positioning
scan parameters
contrast media
other drugs
post procedure care

Question 2

patient preparation for CT Abdo

Answer 2

cannulations - rule out contraindications first
check they’ve followed prep instructions - have they taken picolax? has it worked?
oral contrast/water
explanation

Question 3

why are oral contrast agents used

Answer 3

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

Question 4

what would minimise the risk of aspiration

Answer 4

use of naso-gastric tube to administer oral contrast

Question 5

what is the patient prep for CT Abdo - 5 points

Answer 5

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

Question 6

what else is used in patient prep for CT Abdo

Answer 6

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

Question 7

when should oral contrast not be given

Answer 7

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

Question 8

patient preparation for rectal contrast media

when should it not be given

Answer 8

diluted gastrografin
diluted iodinated contrast
gas - O2 or CO2

in patients with recent colonic or rectal surgery

Question 9

what additional patient prep is required for CTC

Answer 9

Picolax and low residue diet - 48 hours, - to clear bowel of faecal residue

Question 10

what additional patient prep is required for CT IVU

Answer 10

hydration of patient prior to exam to improve distention of urinary tract and provide optimal visualisation of the kidneys

Question 11

why can patient positioning be varied between prone and supine - 2 points

Answer 11

to remove overlying fluid or faeces which may mimic or obscure pathology
to see if renal stones move

Question 12

why scan on arrested respiration

Answer 12

to reduce movement artefact

Question 13

describe iv contrast media

Answer 13

helps identify blood vessels, anatomy, pathology

Question 14

give 3 examples of iv contrast media

Answer 14

niopam, omnipaque, visipaque

Question 15

contraindications for iv contrast media

Answer 15

renal compromise
diabetes
any previous adverse reactions
asthma/hayfever

Question 16

what is a Hickman’s line

Answer 16

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

Question 17

describe creatinine - 4 points

Answer 17

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

Question 18

Describe eGFR

Answer 18

estimated glomerular filtration rate
based on creatinine level, age, sex, race 
< 30 = involve renal team
30-60 = ask radiologist
> 60 = normal

Question 19

what is the purpose of contrast-enhanced CT

Answer 19

to find pathology by enhancing the contrast between a lesion and the normal surrounding structures

Question 20

what phases are commonly used for CT Abdo

Answer 20

unenhanced
arterial
portal venous

late/early arterial and late/early venous can also be used to identify particular pathologies

Question 21

describe the arterial phase of a CT Abdo

Answer 21

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

Question 22

describe the portal venous phase of a CT Abdo

Answer 22

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

Question 23

describe contrast media timing

Answer 23

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

Question 24

which procedures require administration of particular drugs and what are they

Answer 24

CT IVU - Frusemide (diuretic - induces urination)

CT colonography - Buscopan (muscle relaxant)

Question 25

post procedure care for CT Abdo

Answer 25

Cannula removal
hydration - following iv contrast
results