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Define contrast radiograph.
radiographs made after contrast material is placed into or around the structrue to be visualized.
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Why do we do contrast radiographs?
confirm or disprove a suspected diagnosis
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What are the three things contrast radiographs can better identify?
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What can contrast radiograph tell about mucosal surfaces?
condition of the inner lining of hollow organs (thickness and regularity, are there ulcers?)
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What are survey radiographs?
plain radiographs with no contrast material
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What must be done preferably immediately before a contrast radiograph?
a survey radiograph
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Why must a survey radiograph must be done immediately before a contrast radiograph?
- to make sure the contrast study is necessary
- check patient prep
- for comparison to the contrast film
- make sure the exposure factors are proper
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Why is patient prep very important for a contrast radiograph?
determines whether the contrast study is of diagnostic quality.
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What are the different things we need to do for patient prep when getting ready for a contrast radiograph?
- remove collars, splints, bandages if possible
- allow patient to urinate and defecate
- clean and dry
- clean out GI tract
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What can happen to the contrast radiograph is a patient is wet, muddy, covered in blood or other debris?
- there will be loss of detail and will have artifacts
- any fluid on the animal will show up as tissue density on the radiograph
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What is the purpose for cleaning out the GI tract before a contrast radiograph?
remove stomach and intestinal contents to give us better detail
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What types of contrast radiographs will we need to clean out the GI tract for?
- GI
- urinary tract
- other abdominal studies
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What are the three different ways to clean out the GI tract?
- fasting
- laxatives, mild cathartics
- enemas
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How long should we fast our patients for a contrast radiograph? How long should we hold off water from the patient? What do we do if the patient is needing fluids and we can't take water away?
- 12 hours minimum
- at least 3 hours
- IV fluids
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Define laxatives.
substances that stimulate evacuation or emptying of the GI tract
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When are laxatives usually given before a contrast radiograph?
given 12 and 24 hours before
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What is a mild cathartics?
laxatives
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What is an example of a laxative? How much should be given for a small dog/cat, medium dog, large dog?
- milk of magnesia
- small dog/cat: 1.0 ml/lb
- medium dog: 0.6 ml/lb
- large dog: 0.3 ml/lb
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What types of enemas can we use?
- mild soapy water
- saline
- Fleet
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Who should we avoid using Fleet in and why?
- cats and small dogs
- causes an electrolyte imbalance
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What are contrast agents used for?
used to opacify or outline structures
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What are contrast agents also called?
- contrast material
- contrast medium
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Define contrast agent.
substance placed into the body to outline a structure not normally seen well on survey radiographs
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What are the general categories of contrast agents?
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What does a positive contrast agent look like on a contrast radiograph?
white
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What are the two different positive contrast agents?
- liquid (solution or suspension)
- barium
- iodine
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Is barium water soluble?
no
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What is barium?
suspension of micropulverized powder in water
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What color is barium?
white
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What are two ways to buy barium?
- powder that we mix ourselves
- premixed
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How can barium be given?
orally or rectally into GI tract
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Which is more irritating, barium or iodine?
barium
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What will happen if barium leaks into tissue through a rupture?
it will cause a granulomatous inflammatory reaction
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What costs more, iodine or barium?
barium
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What is Estophotrast?
barium
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Describe Estophotrast.
- commerically prepared
- thick paste for esophagraphy
- hard to swallow
- coats mucosa well
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Are iodinated compounds water soluble?
yes
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What do iodinated compounds look like?
clear liquid solution
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What two forms do iodinated compounds come in?
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Iodinated compounds are hypertonic. What does that mean?
- tends to dehydrate
- diuresis or draws water into the bowels
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What kind of patients should we avoid iodine in?
dehydrated or debilitated patients
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Does iodine pass through the GI system faster than barium? Why or why not?
- yes
- thinner, more water than barium
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What kind we give patients when using iodine? Why would we do this?
- IV fluids
- keeps them from getting dehydrated
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When is iodine preferred over barium?
when there is a suspected rupture in the GI tract or bladder
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What are two examples of iodine?
- Gastrografin (for gastro)
- Renografin (for urinary)
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What is Gastrografin made of?
meglumine and Na diatrizoate
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What is a contraindication for Gastrografin?
not recommended for cats
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What is Gastrografin used for?
GI studies
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Does Gastrografin coat the GI mucosa wall well?
no
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What is Renografin used for?
urinary tract studies
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What are negative contrast agents?
gases
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What do negative contrast agents look like on a radiograph?
black
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What different gases are negative contrast agents?
- room air
- carbon monoxide
- nitrous oxide
- oxygen
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What are negative contrast agents?
radiolucent
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What are some ways we can give a negative contrast agent?
- can give carbonated beverage by stomach tube (CO2 is released into the stomach)
- pill available to release gas into the stomach (example - Alka - Seltzer)
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What is an air embolism and when can this happen?
- if blood vessels are ruptured, a gas bubble can get into the blood circulation
- can happen with a negative contrast agent
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Are air embolisms common when using a negative contrast agent?
no
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How long does it take for room air, CO2 or N2O to dissolve in the blood when an air embolism occurs?
- room air: up to 2 weeks
- CO2 & N20: in a few hours
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Define double contrast.
use of both positive and negative contrast material in the same structure at the same time
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How do we position a patient for a contrast radiograph?
place the area of interest closest to the film for the clearest image
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When positioning a patient for a thoracic contrast radiograph what should we include?
- first pair of ribs (thoracic inlet)
- through the diaphragm
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When positioning a patient for an abdominal contrast radiograph what should we include?
- diaphragm through hip joints
- hold tail out of the way
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What position is preferred for an abdominal contrast radiograph?
right lateral
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Why is a right lateral preferred for a contrast radiograph?
- allows stomach gas to movve into the fundus
- outlines stomach and liver better than a left lateral
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Why is a left lateral not preferred for a contrast radiograph?
- gas rises into pyloric area and causes smaller, thicker gas bubble
- does not outline the stomach and liver as well as a right lateral
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Other than lateral view, what kind of position should we use for an abdominal contrast radiograph?
VD - frog leg view preferred over extended view
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Why is the frog leg view preferred over the extended view for a contrast radiograph?
- the patient is more relaxed
- the abdomen is not as compressed, organs are spread out a little
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How do we label a contrast radiograph?
the usual information for a radiograph plus sequential studies (upper GI series, IVP, etc), mark time clearly on each film
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Should we use anesthesia for a esophagography? Why or why not?
no, because the patient needs to be able to swallow
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Can we use anesthesia for a myelography?
yes, because it is a contrast study around the spinal cord
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What are some reasons why we would not perform a contrast radiograph on patient?
- stress
- dehydration
- anesthetic risk
- possibility of perforations
- hypersensitivity to contrast agent
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