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
What are the advantages of iodine contrast media?
- Water soluble organic iodine containing preparations
- 2 main groups – ionic, non-ionic
- Intravenous use
- Renal excretion
What are the disadvantages of non-ionic water soluble iodinated contrast media?
- Slightly more expensive
- Viscous
- Side effects may still occur, although rare – anaphylaxis, nephrotoxicity, urticaria, vomiting, pyrexia
What are the negative contrast media? What is their appearance?
Air
CO2
Black on radiograph
What are the advantages of negative contrast media?
- Cheap/free
- Simple to use
- Relatively safe
- Can combine with positive contrast agents – double contrast study
What are the disadvantages of negative contrast media?
- Very small risk of air embolism – possible reduced by performing study in left rather than right lateral recumbency
- Poor mucosal detail
- Produce less contrast than positive contrast agents
What is portovenography used to assess?
Portal vein and tributaries
What is arthrography used to assess?
Joints
What is angiography used to assess?
Blood vessels
What is fistulography used to assess?
Sinus tracts
What are the indications of barium swallow?
Dysphagia
Regurgitation
Suspected rupture
Liquid barium and/or barium food – iodinated contrast if suspected rupture
When is there is a risk of aspiration of barium swallow?
If swallowing problem, struggling, respiratory stress, weak
What is a barium follow through study?
- Evaluates stomach and small intestine
- Liquid barium
- By mouth or stomach tube
- Radiographs taken immediately and then at intervals depending on transit time
- Final images at 24 hours or when all barium in colon
What are the indications for barium GI tract studies?
- Vomiting – persistent, recurrent, haematemesis
- Palpable mass
- Abnormality suggested by survey films
What are the complications of barium GI tract studies?
Constipation – rare
Aspiration – if given by mouth
What are barium enemas?
- Evaluates the large intestine
- Need to do a full enema before hand
- Liquid barium infused into rectum post enema – can follow with air (double contrast)
- Messy and difficult to interpret
- Ultrasound can be used to assess colonic wall
- Technique superseded by ultrasound and colonoscopy – could modify to identify colon with small volume contrast if unclear on plain radiograph
What are the minimal complications of barium enemas?
Leakage, rarely over-inflation with air causes rupture
How can the kidneys be delineated in dogs and cats on x-ray?
Dog wrapped up in caudal lobe of liver and cats have lots of retroperitoneal fat that can help delineate the kidneys
How are the size of the kidneys determined?
Measure with respect to length of L2:
Dogs 2.5 – 3.5 x L2
Cats 2.4 - 3 x L2. 2 x L2 in some ‘normal’ older cats but this doesn’t exclude subclinical renal disease
What does mineralisation on the kidneys indicate?
Could be nephroliths or damaged parenchyma. Perfectly circular is more likely to be nephroliths.
Where should the bladder normally lie?
Entirely within the abdomen
What is the consequence of the neck of the bladder around the level of the pelvic brim?
Intrapelvic = incontinence (female)
When might there be changes in opacity on plain studies of the bladder?
Radiopaque calculi = increased radiopacity
Emphysematous cystitis = decreased radiopacity
What are the indications of contrast studies when viewing the bladder?
- Wall thickness
- Mucosal surface
- Filling defects
When are plain and contrast radiographs used to view the urethra?
Plain radiograph – if calculi
Retrograde contrast study – rupture, urethritis/tumour, stricture
What can be confused with urethral caliculi in dogs from lateral radiographs?
At similar level at back end of dog is the favellae on the back of the stifle
Why can you not use ultrasound to image the urethra?
Not amenable to ultrasound as most of the urethra pertains in the pelvis
When might the prostate be visualised on radiographs?
Intra-pelvic may not be visible, intra-abdominal if enlarged
When are changes in prostate size, shape and opacity seen?
Size <70% sacral promontory to pubic brim indicates pathology
Shape – symmetrical around urethra on contrast study. Hyperplastic will enlarge symmetrically, not with neoplastic enlargement
Opacity – mineralisation or gas
What are the differential diagnoses for prostamegaly?
- BPH – benign prostatic hyperplasia
- Prostatitis
- Abscess
- Neoplasia – possible concurrent vertebral bone changes
- Paraprostatic cyst – usually seen as separate soft tissue masses, may mineralise
What do cavitated lesions with leakage of contrast in the prostate indicate?
Abscessation, neoplasia or cystic structures that interfere with the urethra.
What is the cause of an enlarged uterus?
Pregnant, recent parturition, pyometra
What is the position of the uterus?
Dorsal to bladder and ventral to colon, only thing could be uterine horns even though can look like intestine
What is seen on radiography at 3 weeks to 6.5 weeks of pregnancy?
3-4 weeks – round soft tissue ‘masses’
5-6 weeks – large coiled tubular structure
6 – 6.5 weeks – foetal mineralisation
Name 3 urinary tract contrast studies.
Intravenous urography
Cystography
Urethrography
What mediums are used for urinary tract contrast studies?
Use water-soluble iodinated contrast medium. Never barium as you can’t use IV suspension, irritant in bladder (granulomatous cystitis).
What is excretory urography?
- Identify/assess kidneys
- Assess ureters
- Vesicoureteral junction
- Bolus of contrast given into peripheral vein
What are the indications for excretory urography?
- Persistent urinary tract infections
- Urinary incontinence
- Haematuria
- Suspected renal abnormalities – survey films, palpation
What are the radiographs taken in excretory urography?
- Immediately: nephrogram (VD)
- 5 minutes: pyelogram (VD)
- 10 minutes: ureterogram (lateral)
- 15 minutes: ureterovesicular junction (lateral)
What is the appearance of the ureter?
Ureter looks like golf club at base. If you see in entirety, likely to be dilated
What are the complications of excretory urography?
Contrast-induced renal failure
- Failure of renal pelvis/ureters to opacify
- Start IV fluids and administer diuretics
- Usually reversible
Anaphylaxis
How are renal cysts seen on radiographs?
- Fill with contrast if communicate with collecting system
- Otherwise seen as radiolucent areas
Define hydronephrosis.
Renal pelvis is very dilated and dilated ureter
What is cystography?
- Delineates bladder
- Contrast introduced via urinary catheter
What agents are used for cystography?
- Pneumocystogram– air only. Bladder location, shows large masses/marked thickening
- Positive contrast cystogram– iodinated contrast. Leakage?
- Double contrast cystogram – both agents. Delineation of wall and content
What are the indications for cystography?
- Dysuria
- Haematuria
- Persistent UTIs
- Pelvic trauma
- To identify bladder – if displaced into rupture/hernia
What are the potential complications of cystography?
- Iatrogenic rupture (care with not over-filling)
- Damage to mucosa by catheter tip
- Air leakage into broad ligament (not serious)
- ‘Knotting’ of catheter
- Catheterisation of ectopic ureter or reflux – may lead to pyelonephritis
- Air embolism (rare) – minimise risk by keeping animal in left lateral recumbency, as potentially keeps air on right ventricular outflow tract instead
What is double contrast of the bladder?
Positive contrast forms puddle and sticks to any wall ulceration and air around the outside within the bladder
What urethrography is done in male and female animals?
Vagino-urethrography in females and recto-urethrography in males
What is urethrography?
- Delineates urethra (and vagina)
- Water-soluble iodinated contrast medium
- Introduced via Foley catheter into distal urethra/vestibule
- Radiograph taken at end of injection
What are the indications for urethrography?
- Dysuria
- Haematuria
- Persistent UTIs
- Pelvic trauma
- To identify bladder – if displaced into rupture/hernia
What is a possible complication for urethrography?
Urethral damage
When might the vagina distend with contrast on urethrography?
If close to oestrous, very distensible and may cause uterus to fill with contrast too. May interfere
What are the responses of bone to injury?
- Bone loss/production
- Fractures/luxations
- Nutritional bone disease
What is assessed from soft tissues on radiographs to evaluate the limbs?
Alignment
Cortices
Medulla
Articular surfaces
Immature animals
Swelling
Joint effusion
Muscle wastage – chronic not acute
Foreign material
Gas
Mineralisation
Which is the only joint where we can identify intra-articular soft tissue opacity and how?
Only in the stifle, other joints cannot tell if there is an effusion. 2 things that help is determine if there is effusions in the joint:
- Infrapatellar fat pad
- Fascial planes
How is alignment of bones checked?
- Check alignment of bone with adjacent bones – 2 radiographs in each plane in order to check this accurately
- Positioning can alter appearance
How is alignment of bones altered with cruciate rupture?
Small projections on the tibia should meet the femoral condyles in normal. If cruciate rupture, these projections no longer align with the femoral condyles
What things are assessed with cortices from radiographs?
- Overall shape of bone
- Continuous?
- Nutrient foramen – not fracture
- Thickness?
- Periosteal surface – abnormal prominence or irregularity?
- Endosteal surface
When might the periosteal surface of cortices be abnormal?
Periosteal surface should be straight and smooth, might not be if infection causes sequestrum
What is assessed with medullary bone on radiographs?
- Integrity of trabecular pattern?
- Changes in opacity
What is panosteitis?
- GSD overrepresented
- Affects medulla of long bone
- Typically shifting lameness – difficult to distinguish on manipulation of the limb of holding the long bone and pain in the joint being manipulated
- Radio-opaque areas of increased opacity are the abnormal areas
What is assessed at articular surfaces of radiographs?
Contours of surfaces
Subchondral bone
Congruity
What is a consideration of radiographs of bones in immature animals?
- Open physes
- Don’t mistake for fractures
How does bone loss in response to injury/disease present?
- Overall opacity reduces relative to soft tissues
- Thinning of cortices
- Loss/thinning medullary trabeculae
- Need approximately 40% mineral loss before radiographically apparent
What are the causes of multi/focal bone loss?
Infection
Neoplasia
Trauma
What are the causes of diffuse bone loss?
Disuse
Nutritional/metabolic
What are the causes of bone production?
Trauma
Fracture healing
Neoplasia
Infection
Miscellaneous
How might the distribution/characterisation of bone production indicate cause?
Pattern – smooth (benign/chronic) vs. spicular (active/aggressive)
Margination and transition to normal bone – long ‘zone of transition’ with aggressive lesions
How is bone distinguished from dystrophic calcification of soft tissues?
Trabecular structure/location
Distinguish the radiographic appearance of aggressive and benign neoplastic conditions of bone.
Aggressive:
- Mixed production/destruction
- No well defined margin to lesion
- Long ‘zone of transition’
Benign:
- Well marginated
- Short ‘zone of transition’
- Smooth, thinned cortices
- Expansile but no cortical destruction
What is craniomandibular osteopathy/lion jaw?
- Terrier breeds
- Immature animals
- New bone on – mandible, tympanic bullae, calvarium
What is hypertrophic osteopathy?
New bone production on the limb in response to a space occupying lesion in the thorax or abdomen
What is calcinosis circumscripta?
Soft tissue mineralisation on pressure points that mimics bone pathology. Mineralisation not associated with bone itself, just the surrounding soft tissues, superimposed onto the bone
How are fractures classified?
- Orientation – transverse, oblique, spiral
- Number and position of fragments - simple vs. comminuted. Distracted, impacted, overriding
- Involvement of growth plates? Salter-Harris classification
- Involvement of articular surfaces?
How are fracture positions described?
Describe a fracture distal part relative to proximal
How are fractures aged using radiography?
- Recent – ends well-defined
- 7-10 days – rounder, less well-defined ends
- 10-14 days – periosteal new bone
- 4-6 weeks – bony union
- Remodelling thereafter
What is the radiographic appearance of nutritional secondary hyperparathyroidism?
- Generalised decrease in bone opacity
- Thin cortices
- Pathological complete or folding fractures
- Normal growth plates
What is the radiographic appearance of renal secondary hyperparathyroidism?
- Due to chronic renal failure
- Similar radiographic appearance
- Skull most affected (rubber jaw)
- Usually older animals
What are the radiographical features of rickets?
- Wide physes – especially distal radius/ulna
- Flared metaphyses
- Overall mineralisation often normal
What are the radiographic features of hypervitaminosis A?
- Periosteal new bone - cervical spine, rest of spine, limb joints
- Can cause fusion
- Remodel but don’t resolve when diet corrected
How is the spine evaluated on radiograph?
- Positioning/centring important is important for the spine – spine straight
- Means GA in most cases
- To ensure the primary beam passes straight through the disc spaces, several images should be taken
What is the consequence of spina bifida?
Caudal contour and alignment has abnormalities which are likely to have impact on the vertebral canal and the spinal cord nerve roots at that level
What is the cause of fluffy new bone appearance on radiographs?
New bone secondary to infection and reactive change
What changes can you look for for the subtle changes in the spine?
Compare adjacent vertebrae, the trabeculae structure and the overall opacity
What is the radiographic appearance of the normal intervertebral foramen?
Radiolucent
Shape of radiolucency analogous to horse’s head
Describe intervertebral disc space width on radiographs.
Look at vertebrae in the centre of the radiograph, expect these to narrow towards the periphery of the image because of the x-rays beam diverging and going obliquely through those disc spaces.
What does myelography do when imaging the spinal cord?
Delineates subarachnoid space
Localises lesions of spinal cord
- Medullary lesions
- Lesions compressing cord – intra-dural or extra-dural
Which contrast mediums are used for myelographing the spinal cord?
Non-ionic water-soluble contrast medium – Omnipaque, Niopam
Ionic contrasts contraindicated as they cause seizures and local inflammatory change leading to arachnoiditis
What are the indications for myelographing the spinal cord?
- Neurological dysfunction
- Spinal pain
- To further define lesions suspected on plain radiograph – disc calcification/narrowing
What are the complications for myelographing the spinal cord?
- Spinal cord damage (intramedullary injection)
- Haemorrhage into cord
- Infection (meningitis)
- Seizures – meningeal irritation
- Worsening of existing neurological signs
What are extra dural lesions of the spinal cord most common caused by?
Extra dural lesion most commonly disc extrusion/protrusion
What are intramedullary lesions of the spinal cord caused by?
Another that caused compression of the cord, such as cord oedema, myelitis, neoplasia
What are extra and intramedullary lesions of the spinal cord caused by?
Nerve root tumour, meningioma
How can the left and right side of the thorax be differentiated on radiographs?
Vena cava goes through right side of diaphragm. If on left, left lung squished so left side of diaphragm and stomach seen on left (do not interpret as pathological), crura form more of a V on the left and right more parallel lines.
How can VD and VD views be distinguished?
DV view – single continuous dome, gas in stomach seen
VD – not continuous dome, more lumps, gas in stomach less easily seen
What are some typical anatomical differences between cat and dog radiographs?
- Tympanic bullae - extra bone in cats to compartmentalise bulla
- Patellae - elongated in cats (would be arthritic osteophytic change in dogs)
- Caudal lung field - normal in cats to have caudal tip move away from spine (would be pleural fluid in dogs)
- Cats have clavicles, dog do not
- Variation in costochondral junctions - look ragged in dogs, thinner and T shaped in cats
- Gas in stomach and intestines – usually less in a cat
- Falciform fat – more prominent in a cat
Which organs, if normal, cannot be identified radiographically?
Pancreas
How is intestinal distension identified?
Roughly depth of normal TL end plate, less tan twice the width of the 12th rib, not twice the width of any other areas, less than 12mm in the cat
How is an enlarged heart shown on thoracic radiograph?
Dorsal enlargement related to enlarged LA. Normal has smooth curve to caudal margin but this once has some indentation so taller heart with caudal indentation is dorsal enlargement.
What is the most likely cause of a very round globular cardiac silhouette?
Pericardial disease or generalised disease with some cardiomyopathy are high on differential list - neoplastic and idiopathic causes, including haemangiosarcoma, aortic body tumours and mesothelioma
What contrast can you use for an intravenous excretory urogram?
Non-ionic iodine based – animal with any renal disease, non-ionic has less complications
Where should the bladder be positioned?
Should be just in front of pubic bone. USMI with neck going back into pelvis, hasn’t got normal pressures around the neck = incontinence in itself
How is the stomach used to distinguish left and right lateral?
Left lateral - gas would move into the pylorus. Useful is you think FB in pylorus
Right lateral - fluid in the stomach and pylorus is quite a round structure
How are opacities on radiographs used to assess the heart?
Gas opacity ventral to cardiac silhouette, can see contrast between these. Fat would look greyer but would still see border. Fluid would see not edges at all and contrast is lost.
Why do we see the serosal margins of normal organs?
Fat
How is an aggressive bone process indicated on radiographs?
Bone loss and margins are ill defined
Long zone of transition
