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L9 Clinical imaging of the gastrointestinal tract (Imaging Modalities…
L9 Clinical imaging of the gastrointestinal tract
Why do we need to image the GIT?
Animals presented for:
–Vomiting
–Diarrhoea
–Inappetance
–Weight loss
Abdominal radiographs can help the clinician make a definitive diagnosis or decide between medical or surgical treatment. However, radiographs should not take precedence over a complete history, a thorough physical examination and pertinent laboratory tests
Eg.
In a vomiting dog we need to decide on surgical vs medical treatment
If the GIT is obstructed surgery is indicated, if not- medical management is required.
Assess for radiographic evidence of ileus (lack of peristalsis)
–May be due to an obstruction or due to a functional disorder
Functional, Paralytic or Adynamic Ileus
Due to decreased or absent peristalsis (no blockage)
Causes: vascular or neuromuscular abnormalities which may be caused by electrolytic imbalances, gastroenteritis, pain
Obstructive or Mechanical Ileus
Due to partial or complete obstruction of the GIT
Common causes:
Foreign body such as corn cob, string
Mass such as neoplasia
Intussusception
Imaging Modalities
Radiology
Xrays are passed through the full thickness of the patient
Naming the radiograph
Abdomen
–Right laterally recumbent, the “right lateral”
–Left laterally recumbent, the “left lateral”
–Ventrodorsal
–(Dorsoventral)
Principle
Always display radiographs with the head to the left of screen if a lateral projection
Always place head at the top of screen and right side of patient to the left if a VD/DV radiograph
“Rules and sayings”
Dogs
Ratio of greatest SI diameter to body of L5 no > 1.6
No loop greater than twice the width of others
Cats
No greater than 12 mm in diameter
No greater than twice the height of L4
Reading
Dark room
Away from distractions
organs graph (see slides)
Radiographic Interpretation
Assess: The Roentgen signs
Size – degree of distension
If distended
• How distended?
• How much of the GIT is affected?
Shape
Margins
Location
Opacity
gas, ingesta, foreign material
Number
Case Study
• 8 year old Border Collie
• Vomiting for 4 days
• Dull and dehydrated on presentation
case1
• 2 year Labrador
• Sitting on couch with owner and toy
• “Tigger” disappeared
• Owner brought dog straight to us
case2
• 8 week old Golden Retriever puppy
• Owned by vet nurse
• Presented with 3 day history of vomiting and diarrhoea
• Dehydrated on clinical examination
• Blood flecked faecal staining on coat
case3
• Larry
• Lives in a cattery
• Noted to be vomiting this am
• Mass palpated in abdomen on examination
case4
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Ultrasound
High frequency sound is pulsed into the patient and an echo is received and displayed on the monitor
Scintigraphy (Nuclear Medicine)
Radiopharmaceutical injected into patient and radiation coming out of patient is detected by the gamma camera and processed by the computed into the image
SI Normal Ultrasound Appearance
Computed Tomography (CT)
A fine beam of xrays is passed through the patient, detected, sent to a computer for processing and an image is produced
Magnetic Resonance Imaging (MRI)
Magnets and radiofrequency waves
