Approach to abdominal imaging and imaging of parenchymal organs Flashcards
Why would be want to image the abdomen?
- Biopsy
- Hernias
- Stomach torsion
- Pregnancy
- RTAs
‘What are radiographic considerations?
- Low kV-high mAs technique to avoid scatter radiation and improve contrast resolution
- Intrinsically poor contrast mostly soft tissue with only
a little fat to give contrast - High/long mAs increases susceptibility to motion artefact
- Expose during expiratory pause (end of expiration)
- VD instead of DV view to “spead out” organs
- reduce superimposition
- Remember: “One view is one view too few!”
- Take a right lateral and ventrodorsal projection
What is contrast medium - advantages/disadvantages?
- Helpful for urinary tract studies
- Rarely useful in gastrointestinal tract studies (use ultrasound)
- Essential for abdominal CT
- Require good preparation and time and money!
- Correct contrast medium for the right indication
What are positive contrast media (bright)
- Iodine containing - GIT, urinary tract + myelography = SAFEST
- Barium - GI only
What are negative contrast media? (dark)
- Room air - limited use
- CO2 or N2O
What happens if barium escapes?
- Severe granulomatous inflammation + death
What can use of gas / air cause?
- Fatal air embolism - on rare occasions
What are ultrasound considerations?
- Great soft tissue contrast - shows internal architecture
- Operator dependent - experience necessary
- Gas is the death of US
For best results:
* Perform AFTER radiography (gel artefact)
* Sedate
* Well set-up and quiet, dark room
* Clip widely
* Use plenty of gel
Where are blind spots with ultrasound or radiography?
- Organs within the pelvic canal
- Assessment of surgical accessibility
- Vascular malformations (e.g. portosystemic shunts)
- Ectopic ureters
- Refer for CT
What are Rontgen signs?
- Number
- Size
- Shape
- Margination
- Opacity - (gas, fat, soft tissue, bone/mineral, metal)
- Location
What would you consider before diagnosis?
- normal anatomy
- Pattern of pathology
- Radiological findings
- CLinical history + signalment
What are the different opacities?
- Gas = darkest
- Fat
- Fluid + soft tissue
- Mineral
- Metal = brightest
What is mass effect?
- Gives clues about the origin of masses/space- occupying lesions or in some cases that there is a mass at all
- Displacement of other organs
What are 3 forms of mineralisation?
- Dystrophic - secondary to tissue damage
- Metastatic - secondary to hypercalcaemia
- Other
What are examples of dystrophic mineralisation?
PREVIOUS PROBLEM
* Adrenal (cats)
* Fat necrosis (bates bodies)
* Of tumour, abscesses …
- Usually see a focal lesion
What are examples of metastatic mineralisation?
CURRENT PROBLEM
* Toxic
* Uremia (gastric)
* Paraneoplastic - secondary to a tumour - lymphoma
- Usually see mineralisation of gastric wall
What are examples of other mineralisation?
- Urinary calculi
- Ingesta
- Osseous neoplasia
What can cause loss of serosal detail?
- lack of fat = effacement - no margination of organs
- Peritoneal fluid - secondary to R-CHF
- Brown fat / young animals - contains a lot of water
- Peritonitis
- Carcinomatosis / sarcomatosis - micronodules in organs replace fat
- Visceral crowding
What causes pneumoperitoneum?
- Post surgery - up to 4 weeks
- Ruptured GIT - septic abdomen
- Penetrating trauma
What is seen with pneumoperitoneum?
Increased contrast between gas + soft tissue
- diaphragm + intestinal walls more obvious to see
* Gas bubbles not within GIT
* Loss of serosal detail
What is seen with the liver on radiograph?
- Most cranial organ
- Acute ventrocaudal angle
- Just poking past the costal arch
- Gastric axis:
-Fix a point in the middle of the fundus
-Draw a line to the middle of the pylorus
What is seen with hepatomegaly?
Generalised
* Rounded margins
* Extending further caudal to the costal arch
* Caudally displaced gastric axis
e.g. nodular hyperplasia, lymphoma, acute hepatitis, metabolic hepatopathy
Focal
* Mass effect depending on which part is affected
e.g neoplasia, abscess
What is small liver called? What is seen?
MICROHEPATIA
- Contained within the costal arch
- Little soft tissue cranial to the stomach
- Cranially displaced gastric
What can cause microhepatia?
- Vascular - portosystemic shunt / primary portal vein hypoplasia
- Inflammatory - chronic hepatitis with fibrosis/cirrhosis
What does the normal spleen look like?
- Tail: Flat triangle just caudal to the liver ventrally = mobile
- Head: Flat triangle on the left, ‘superimposing’ the right kidney = fixed to stomach
- Body: connecting both, left, often not clearly visible
What is seen with splenomegaly?
- Subjective assessment of size
- Often rounding of the margins
- Tail caudally displaced
- In cats: Tail visible ventrally!
What is seen with a normal retroperitoneum?
- Dorsal to the peritoneal cavity
- Contains kidneys and ureters, bladder neck, great vessels, adrenal glands and lymph nodes, prostate etc.
- Continuous with mediastinum cranially
- Normal fat opacity (often streaky)
What can cause splenic masses? (abnormal shape)
- Neoplasia (dog = haemangiosarc, cat = MCT)
- Haematoma
- Nodular hyperplasia
What can cause generalised splenomegaly? (normal shape)
- Sedation / GA
- Infiltration - lymphoma
- Inflammation - hyperplasia + splenitis
What are retroperitoneal masses?
- Can arise from any retroperitoneal organ (common kidneys and lymph nodes)
- Or can be fluid (effusion/haemorrhage)
- Mass effect: Displacing peritoneal organs ventrally
- Abnormal soft tissue opacity
Adrenal glands are not visible on radiographs, when might you see them in cats?
- Old cats = mineralised adrenal glands
What are adrenal masses?
- Mineralisation in dogs is associated with neoplasia (but not all tumour mineralise)
- Mass effect: displace kidney laterally and/or ventrally
- Common neoplasia: adenoma/-carcinoma and phaeochromocytoma
What is seen with lymph nodes on radiograph?
What are the retroperitoneal + peritoneal lymph nodes?
- Normally not visible on radiographs
- Mass effect when enlarged
- Soft tissue mass
- Retroperitoneal lymph nodes
para-aortic (including renal), medial iliac, internal iliac, sacral - Peritoneal lymph nodes
gastric, pancreaticoduodenal, splenic, jejunal and colic
