Diagnostic Imaging Flashcards
Why are abdominal boundaries assessed on diagnostic imaging?
Checking for evidence of rupture or herniation and if boundaries are intact.
What are the differences between imaging cats and dog abdomens?
- Cats have quite prominent areas of falciform and retroperitoneal fat that isn’t so common in a dog
- In the dog, the spleen lies in a slightly different position to the cat and tail of the spleen usually curls around in the mid-ventral abdomen
- Spleen less commonly visible in cats
What is indicated by serosal detail in the peritoneal cavity?
Good if fat
Poor if young/thin, peritonitis, fluid or neoplasia
How is serosal detail assessed?
- Check body condition – intra-abdominal fat, fat over spinous processes
- Distension of abdomen – unlikely if very thin animal
- Free gas – possible GI rupture, previous surgery/trauma
Why do puppies and kittens have little serosal detail?
Have rounded bellies but have a general lack of fat and increased proportions of brown fat so little serosal detail.
Where is the spleen visualised on radiographs?
- Head to caudal to stomach on left (see on VD)
- Tail usually mid ventral abdomen (lateral view)
What does the size of the spleen on diagnostic imaging depend on?
Sedation, position, individual/breed variation
Where is the splenic head visualised on radiographs?
- Smooth triangle in left cranial abdomen
- Caudal to stomach
- Cranial to left kidney
Why is diffuse splenomegaly hard to assess radiographically?
Wide normal range, overlap maximum normal/minimum pathological size, subjective
What is the appearance of diffuse splenomegaly?
- Rounded edges
- Displacement of other viscera
What is the appearance of splenic masses?
- Generally quite visible radiographically
- Small intestine displaced caudally or dorsally
- Very vascular so may bleed causing free fluid and so poor detail
What is the appearance of the liver on radiogrpahs?
- Roughly triangular in shape
- Soft tissue opacity
- Smooth distinct margins
- Ventral lobe – not too rounded, approximately at level of costal arch
How is the gastric axis used to assess liver size?
Normal is perpendicular to spine and parallel to the ribs, breed variation in dogs, so if liver falls between these lines it is likely to be normal
When might the gall bladder be visualised on radiographs?
In cats
What are the differential diagnoses of small livers?
- Portosystemic shunt – which may be associated with large kidneys in dogs
- Cirrhosis
- Chronic hepatitis
What are the differential diagnoses of large livers?
- Acute hepatitis
- Endocrine hepatopathy – such as cushing’s
- Congestion
- Infiltrative neoplasia
- Focal mass lesion
What is the appearance of the stomach on radiographs?
- Lies in cranial abdomen
- Caudal to liver
- Long axis – parallel to ribs
- Fluid/gas distribution varies with position
Where is the stomach located on radiographs?
- Hiatal hernia
- Gastro-oesophageal intussusception
- Diaphragmatic rupture
- Dilation vs volvulus
What does content and transit time from a radiograph indicate about the stomach?
Contents – radiopaque foreign material?
Transit time of food/liquid – outflow obstruction?
Why are plain radiographs often unrewarding?
Wall can’t be delineated from fluid content unless there is rugal calcification
What does a single stricture without subdivision suggest about the stomach?
Tells us it is dilation rather than a volvulus
What are the measurements for the small intestine on radiographs?
Variable diameter loops usually around twice the width of a rib and equal to the depth of a vertebral end plate
What are the measurements for dilated small intestine on radiographs?
Ratio of width SI to heigh of mid-body of L5 – SI:L5 < 1.4 = very unlikely to be obstructed, SI:L5 > 2.4 = very likely to be obstructed
Ratio of width of largest and smallest loops - <2 very unlikely to be obstructed, >3.4 very likely to be obstructed
Why are chronic partial small intestinal obstructions harder to diagnose?
As there is some obstruction of width but contents can still past through
What are the clinical signs of chronic partial small intestinal obstructions?
- Gravel sign
- Chronic build up of ingesta over time
- Contents looks like faeces but not in colon
What are the differential diagnoses of chronic partial small intestinal obstructions?
Intussusception, foreign body, tumour, stricture
Where is the colon located in the abdomen?
- Ascending – right mid/abdomen
- Transverse – crosses caudal to stomach
- Descending – left abdomen
- Rectum – within pelvic canal
What are the measurements of the colon in cats and dogs?
In dogs, the colonic width should not exceed 3 times that of normal small intestine, the length of the body of L7, >1.5 x is likely to indicate dysfunction
In cats, colonic width - <1.3 x length of L5 suggests normal, >1.5 x length is a good indicator of megacolon
What are plain radiographs useful for assessed in the colon?
Size (megacolon?), shape, contents, position
What are contrast media?
Agents that are more or less opaque than surrounding tissue. They delineate organs/cavities within the body
What are the purposes of contrast media?
- To see structures not normally visible or poorly visible – ureters, urethra, spinal cord
- To gain more information about soft tissue structures – bladder, kidneys, GI tract
Distinguish positive and negative contrast media?
Positive contrast – high atomic number
Negative contrast – low density
What are 2 positive contrast media?
Barium
Iodine
What are the advantages of barium contrast media?
- Used in GI tract
- Inert, non-toxic
- Reasonably palatable
- Cheap
- Good mucosal detail – liquid barium
- No osmotic effect