SA GI radiography and Ultrasonography Flashcards
What are the advantages and disadvantages of GI radiography?
Advantages:
- Gives a global overview
- Assessment of adjacent thorax and skeleton
- Good for detecting gas or mineralisation
- Very useful for acute conditions (particularly vomiting)
- Cheap and widely available
Disadvantages:
- Superimposition of structures
- Lack of inherent radiographic contrast (cf. thorax)
- Soft tissue and fluid appear the same (water radiopacity)
- Magnification
- Less useful for chronic conditions (particularly diarrhoea)
Describe radiographic technique challenges?
Challenges include:
- Low inherent contrast (soft tissue/fluid and fat)
- Low kV
- Minimising scattered radiation
- Low kV, collimation, use of a grid
- Avoiding movement blur
- Appropriate chemical and physical restraint
- Adequate patient preparation
- Fasted, empty bladder and bowels, clean coat
- 24 hours starvation if possible (free access to water)
Describe good radiographic technique for GI?
- Two orthogonal views: one lateral and a VD
- So the organs spread out
- Centre on the caudal border of the last rib
- Take the radiograph during the expiratory pause
- The diaphragm is most cranial so the organ spread out making them easier to see
Describe GI and Liver contrast studies?
- Document function by taking of sequential still images (e.gbarium series) or using real-time radiography (fluoroscopy)
Gastro-intestinal tract*
- Barium swallow (fluoroscopy)
- Gastrography(air, barium or double contrast)
- Barium series (or “follow-through”)
- Barium enema
- Pneumocolon
Liver
- Mesenteric portovenography(water- soluble iodine)
* Water-soluble iodine may be used with suspected perforations
What GI strucures are visible and not visible in radiography?
The following structures are normally visible in survey radiographs:
Liver, stomach, spleen, kidneys (right variable in dogs, esp. cranial pole), small intestine, caecum, colon, urinary bladder, prostate gland, diaphragm, body wall, sublumbar musculature, thoracolumbar/lumbar vertebrae, caudal ribs, part of bony pelvis.
The following structures are not normally seen in survey views:
Adrenal glands (occasionally calcified in cats), gall bladder, ovaries, uterus, mesentery, mesenteric lymph nodes, omentum, pancreas, abdominal aorta, abdominal vena cava.
The most important GI landmarks are?
The most important landmarks are:
- Liver
- Stomach
- Spleen
- Kidneys
- Small intestines
- Colon
- Urinary bladder
Should be able to see these structures on a radiograph if we can’t see we ought to think why they are being displaced or hidden
What are the advantages and disadvantages of GI ultrasound?
Advantages:
- Assessment of internal architecture and vasculature
- Real time assessment/motility
- Good soft tissue definition
- Accurate measurement
- FNA/biopsy guidance
Disadvantages
- Limited field of view
- Difficult with large amounts of gas
- Very equipment and operator dependent
Ultrasound and radiography are complementary as the advantages and disadvantages of each are different
Increasing the frequency of an ultrasound probe results in?
Less tissue penetration and more definition. So use highest frequency that allows you to see tissue of interest.
What are radiographic and ultrasound signs to observe?
Radiographic signs
- Number
- Location
- Size
- Shape
- Margination
- Radiopacity
- (Internal architecture)
- (Function)
Ultrasonographic signs
- Number
- Location
- Size
- Shape
- Margination
- Echogenicity
- Internal architecture
- Function
Radiographic changes are often due to?
- changes in the size and shape of adjacent structures
- the presence of an abnormal structure
- the absence of a normal structure
How can ultrasound images be assessed?
Internal architecture
which structure(s) are affected
- e.g. spleen, liver, mesentery
where is the lesion within the tissue / organ
- Peripheral or central, diffuse or localised
- Position in relation to anatomical landmarks e.g. blood vessels
When assessing size of structures on radiography what must be considered?
Remember that several organs can undergo considerable physiological distension
e.g. stomach, bladder, uterus
When comparing to normal sizes what must you be careful of?
Compare to known normals where possible, but beware overinterpretation!
Compare the shape of a normal spleen and an abnormal one on radiography?
Discuss margination with regards to radiography?
- In the normal abdomen, mesenteric fat highlights the serosal surface of the abdominal organs
- Structures of the same opacity in contact with each other will appear to merge into one radiographic shadow = border obliteration (border effacement/silhouette sign)
- e.g. loss of abdominal detail in the presence of abdominal fluid
Discuss margination in ultrasonagraphy?
Describe the lesion in terms of margins and outline
- e.g. –abscesses have a fibrous capsule, clear margins, well defined outline and shape, and are distinct from normal tissue
- malignant tumours may have ill defined margins and irregular contours and are poorly defined from adjacent tissue Margination
How do different tissue appear on radiography?
The thickness of an area determines the opacity. Large amount of gas is more lucent than a small amount.
How should echogenecity be assessed?
- What is the normal echogenicity of the affected tissue?
- Is the echogenicity increased or decreased within any lesion?
- Is the echogenicity normal, increased or decreased in the surrounding tissues?
What is the comparitive echogenecity of liver, spleen and renal cortex in the dog?
Spleen > Liver = Renal Cortex
How should renal architecture be described in ultrasonography?
- Changes in normal architecture
- relate to the normal architecture of that organ
- Is the tissue homogenous or heterogenousin echogenicity?
- Is there increased vasculature?
- relate to the normal architecture of that organ
Discuss the position of the liver in a lateral radiograph?
Roughly triangular in shape with smooth distinct margins
Soft tissue opacity
Demarcated by the diaphragm cranially and the stomach caudally
- Gastric axis should be parallel to the ribs and perpendicular to the spine (lateral)
- perpendicular to the spine (VD)
Ventral lobe
- Fairly sharp angle
- Contained within costal arch (caudal edge)
- May see gall bladder ventrally in cat
What can be seen here?
Hepatomegaly
- Projection of caudoventral margin of liver well beyond the costal arch
- Rounding of caudoventral angle
- Caudal displacement of stomach axis
What is wrong here?
Small liver
- Cranial displacement of stomach
- Absence of caudoventral angle
- Significance dependent on clinical signs, etc.
If liver looks small may be due to breed as deep chested e.g sighthounds
