salivary gland and ST imaging Flashcards
reasons for imaging salivary glands
obstruction
dry mouth e.g. SS
swelling
causes of obstruction
mucous plugs
salivary stones/sialoliths
neoplasia - secondary obstruction
causes of swelling
obstruction
neoplastic mass
traumatic ranula
sialosis
properties of US
no ionising radiation
high freq sound waves - cannot be heard audibly
sound waves have short wavelength which are not transmittable through air - require coupling agent to help sound waves get into tissues - water-based gel
why is US good for salivary glands?
superficially positioned
can assess parenchymal pattern, vascularity, ductal dilatation or neoplastic masses
- also visualise nearby LNs
can give a sialogogue (ie citric acid) to aid saliva flow
- will allow better visualisation of dilated ducts
which part of which salivary gland cannot be visualised with US?
deep lobe of parotid (deep to ramus)
need CT/MRI
how US works
transducer uses Piezo-electric crystals
vibrates when electrical signal applied - produces high freq sound pressure waves - US
also works in reverse
produces echos which go back to crystals
- as they encounter different tissues in body
converted to image
interpreting US
top skin surface, work deep SC fat below skin hypo echoic - black - muscles hyper echoic - white - calcified stones - stops soundwaves passing through, get posterior shadowing behind calcified material
imaging protocol for salivary gland obstruction
1 - US
2 - plain film (mandibular true occlusal)
- e.g. if clear obstructive history but US not clear, see potential salivary stone on US
3 - sialography
- if considering mucous plug
- look for strictures
obstructive disease symptoms
meal time symptoms - chewy, citrus, sour = worse prandial swelling and pain "rush of saliva into mouth" when swelling resolves bad taste thick saliva dry mouth
usual aetiology of obstruction
sialolith (calcified stone) or mucous plug
what % of sialoliths are associated with the SM gland?
80%
what % of SM stones are radiopaque and what is the implication of this?
80%
see on US and plain film
what is sialography?
injection of iodinated radiographic contrast into salivary duct to look for obstruction
done either with panoramic, skull views (lat oblique or PA mandible) or fluoroscopic approach
what type of contrast is used for sialography?
iodinated
water-based, isoosmolar to cells of body
vol of contrast injected in sialography
v small 1-1.5ml
indications for sialography
looking for obstruction/stricture (narrowing) of salivary duct which could be leading mealtime symptoms
planning for access for interventional procedures (basket retrieval of stones or endoscopy)
risks of sialography procedure
discomfort
swelling
allergy to contrast
infection
risks of sialography procedure - discomfort
going against salivary flow so sore
up to 48hrs after
risks of sialography procedure - swelling
up to 48hrs (if delayed release of saliva)
show pt how to milk gland to allow saliva flow - bimanual palpation
risks of sialography procedure - allergy to contrast
v rare
check shellfish allergy
check if they have had contrast before e.g. CT scan
MRI alternative as no contrast is used
risks of sialography procedure - infection
if pt attends with infection don’t proceed - give ABs and rebook
normal findings sialography - parotid gland
tree in winter
normal findings sialography - SM gland
bush in winter
findings sialography - acinar changes
snowstorm appearance
e.g. SS or chronic sialadenitis
sialography procedure
dilate duct orifice with probe/balloon dilator
insert catheter
inject contrast (small amount first to check no reflux)
take at least 2 images
- contrast phase with cannula in place - can see any blockages/ductal dilatation
- emptying phase with time delay - wait 5mins, drink water, allows gland to work and produce saliva to excrete contrast. if contrast left on emptying phase - shows chronic inflammation and no longer fully fct
contrast phase
with cannula in place
can see any blockages/ductal dilatation
emptying phase with time delay
wait 5mins, drink water
allows gland to work and produce saliva to excrete contrast
if contrast left on emptying phase - shows chronic inflammation and no longer fully fct
interventional e.g. baskets indications
not routinely done in Scotland
option in some cases rather than SR of stone via incision or EO removal of salivary gland (GA and comorbidities)
can attempt to dilate structures
disadvantages of interventional e.g. basket tx
can need multiple attempts and stenting to keep duct patent, may relapse
sometimes not possible due to extent of scarring from chronic infection - may have endoscopic investigation to see how much scarring
selection criteria for stone removal
stone must be mobile
- if stone adherent to wall you could rip duct - ranula/post-op bleed
stone should be located within lumen on main duct distal to posterior border of mylohyjid (SMG)
stone should be distal to hilum (where gland opens into EG tissues) or at anterior border of the gland (parotid)
duct should be patent and wide to allow passage of stone - no stricture/narrowing distal to stone
proximal
towards gland
distal
towards duct orifice
balloon dilatation
removal of strictures
study
- 87% technical success
- clinical follow up
= 56% complete resolution of symptoms
= 36% some resolution
= 8% unchangedinvestigations for dry mouth (typically pts with suspected SS)
findings used in correlation with other investigations and clinical findings
- blood tests (autoantibodies)
- Schirmer test
- sialometry (measure of saliva flow)
- labial gland biopsy
Scintiscan
nuclear medicine technique - injection of radioactive Technetium 99m
assess how well the glands are working
uptake into the glands if they are working well
SS changes on US
atrophy - shrunk and ill-defined heterogenous parenchymal pattern (leopard print) hypo echoic (darker) fatty infiltration
- chance for MALT lymphoma to develop
swelling 1st line investigation
US to rule out obstruction or neoplasia
take measurements
assess for peripheral or internal vascularity
irregular ill-defined likely malignant
if neoplasia suspected what is required ?
biopsy
FNA for cytopathological diagnosis
if inconclusive/suspect lymphoma - core biopsy for histopathological diagnosis
US guided biopsy - often take 2 passes to ensure adequate tissue sample
if suspect malignancy do neck scan to check cervical LNs
pleomorphic adenoma on US
usually mixed tumours
- solid areas - light grey
- cystic change - black
posterior enhancement - shows mass mostly cystic
ST imaging
US 1st line - possible biopsy if required MRI considered for further investigation - vascular lesions - too large/deep to be seen on US in completeness
what is a ranula?
cystic cavity full of saliva
usually traumatic origin
ranula on US
anechoic/v hypo echoic - v black
area of white posterior enhancement
need to work out size and relationship to mylohyoid to tell whether in sublingual or submandibular space
imaging facial LNs
US good
normal LNs on US
hypo echoic, well-defined
oval
8-10mm max short axis diameter
LNs on US - be suspicious of…
round LNs more likely malignant
irregular/multiple in one region that appear close together or merged
lipoma on US
within SC tissue
well-defined margin
internal hyper echoic striations - parallel to skin surface
a benign lipoma should have no internal vascularity
