salivary gland and ST imaging

Question 1

reasons for imaging salivary glands

Answer 1

obstruction
dry mouth e.g. SS
swelling

Question 2

causes of obstruction

Answer 2

mucous plugs
salivary stones/sialoliths
neoplasia - secondary obstruction

Question 3

causes of swelling

Answer 3

obstruction
neoplastic mass
traumatic ranula
sialosis

Question 4

properties of US

Answer 4

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

Question 5

why is US good for salivary glands?

Answer 5

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

Question 6

which part of which salivary gland cannot be visualised with US?

Answer 6

deep lobe of parotid (deep to ramus)

need CT/MRI

Question 7

how US works

Answer 7

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

Question 8

interpreting US

Answer 8

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

Question 9

imaging protocol for salivary gland obstruction

Answer 9

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

Question 10

obstructive disease symptoms

Answer 10

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

Question 11

usual aetiology of obstruction

Answer 11

sialolith (calcified stone) or mucous plug

Question 12

what % of sialoliths are associated with the SM gland?

Answer 12

80%

Question 13

what % of SM stones are radiopaque and what is the implication of this?

Answer 13

80%

see on US and plain film

Question 14

what is sialography?

Answer 14

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

Question 15

what type of contrast is used for sialography?

Answer 15

iodinated

water-based, isoosmolar to cells of body

Question 16

vol of contrast injected in sialography

Answer 16

v small 1-1.5ml

Question 17

indications for sialography

Answer 17

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)

Question 18

risks of sialography procedure

Answer 18

discomfort
swelling
allergy to contrast
infection

Question 19

risks of sialography procedure - discomfort

Answer 19

going against salivary flow so sore

up to 48hrs after

Question 20

risks of sialography procedure - swelling

Answer 20

up to 48hrs (if delayed release of saliva)

show pt how to milk gland to allow saliva flow - bimanual palpation

Question 21

risks of sialography procedure - allergy to contrast

Answer 21

v rare
check shellfish allergy
check if they have had contrast before e.g. CT scan
MRI alternative as no contrast is used

Question 22

risks of sialography procedure - infection

Answer 22

if pt attends with infection don’t proceed - give ABs and rebook

Question 23

normal findings sialography - parotid gland

Answer 23

tree in winter

Question 24

normal findings sialography - SM gland

Answer 24

bush in winter

Question 25

findings sialography - acinar changes

Answer 25

snowstorm appearance | e.g. SS or chronic sialadenitis

Question 26

sialography procedure

Answer 26

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

Question 27

contrast phase

Answer 27

with cannula in place | can see any blockages/ductal dilatation

Question 28

emptying phase with time delay

Answer 28

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

Question 29

interventional e.g. baskets indications

Answer 29

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

Question 30

disadvantages of interventional e.g. basket tx

Answer 30

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

Question 31

selection criteria for stone removal

Answer 31

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

Question 32

proximal

Answer 32

towards gland

Question 33

distal

Answer 33

towards duct orifice

Question 34

balloon dilatation

Answer 34

``` removal of strictures study - 87% technical success - clinical follow up = 56% complete resolution of symptoms = 36% some resolution = 8% unchanged ```

Question 35

investigations for dry mouth (typically pts with suspected SS)

Answer 35

findings used in correlation with other investigations and clinical findings - blood tests (autoantibodies) - Schirmer test - sialometry (measure of saliva flow) - labial gland biopsy

Question 36

Scintiscan

Answer 36

nuclear medicine technique - injection of radioactive Technetium 99m assess how well the glands are working uptake into the glands if they are working well

Question 37

SS changes on US

Answer 37

``` atrophy - shrunk and ill-defined heterogenous parenchymal pattern (leopard print) hypo echoic (darker) fatty infiltration ``` - chance for MALT lymphoma to develop

Question 38

swelling 1st line investigation

Answer 38

US to rule out obstruction or neoplasia take measurements assess for peripheral or internal vascularity irregular ill-defined likely malignant

Question 39

if neoplasia suspected what is required ?

Answer 39

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

Question 40

pleomorphic adenoma on US

Answer 40

usually mixed tumours - solid areas - light grey - cystic change - black posterior enhancement - shows mass mostly cystic

Question 41

ST imaging

Answer 41

``` US 1st line - possible biopsy if required MRI considered for further investigation - vascular lesions - too large/deep to be seen on US in completeness ```

Question 42

what is a ranula?

Answer 42

cystic cavity full of saliva | usually traumatic origin

Question 43

ranula on US

Answer 43

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

Question 44

imaging facial LNs

Answer 44

US good

Question 45

normal LNs on US

Answer 45

hypo echoic, well-defined oval 8-10mm max short axis diameter

Question 46

LNs on US - be suspicious of...

Answer 46

round LNs more likely malignant | irregular/multiple in one region that appear close together or merged

Question 47

lipoma on US

Answer 47

within SC tissue well-defined margin internal hyper echoic striations - parallel to skin surface a benign lipoma should have no internal vascularity