Please note that the following is a general guideline only.
DEFINITION
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formation of calculi in ductal system of salivary glands
EPIDEMIOLOGY
M > F
age 40 – 70 yrs
Common-SMG: - 80 – 90% of stones
10 – 20% of stones form in Parotid (Stensen's) duct / - 1% in sublingual duct
AETIOLOGY
Uncertain, possible causes can be thought of as local and systemic factors
Systemic-
dehydration- more viscous saliva
Systemic conditions as Sjogrens-
Local
Inflammation/ infection/ duct strictures / taruma- dentures
Above leads top Stasis/ nidus formation
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SMG Stones are More Common: Reasons
Anatomical Factors:
- Duct is: - long & tortuous
- large diameter
- angled against gravity
- narrow at ostium→ slower flow
Physiological Factors:
- SMG Saliva is: - more viscous (higher mucus content)
- more alkaline
- higher in calcium & phosphate
PATHOLOGY
SMG-hard stones (more Calcium), Parotid soft stones (less Calcium)
The initial formation of organic gel, which becomes a framework for the deposition of salts
Salts are mostly calcium phosphate & carbonate, (less Mg, Po4, Ammonia)
CLINICAL (ASSESSMENT = history, examination, investigations)
- Recurrent post-prandial salivary colic (pain & swelling after eating)
- History of multiple cases of acute suppurative sialadenitis
- Bimanual palpation will reveal palpable stone intraorally in most cases
- More common SM stones will be noted along the floor of the mouth
-Parotid stones might be noted at the orifice of Stensen's duct or along its course
INVESTIGATIONS
US is an excellent first line investigation. Below is a summary of other investigations.
XR
- Intraoral or occlusal views identify radiopaque stones - poor predictive value to do the reasons below
- false positives-phleboliths, atherosclerosis of lingual artery, calcified cervical LN
- false negatives-80% parotid stones are radiolucent
US
-Good predictive value in the hands of an experienced radiologist
-Difficulty distinguishing between stones and stenosis (both give a cone beam)
-Can see over the mandible well enough
Digital subtraction sialography
- Can detect radiolucent stones as well, but not routinely done anymore
- The sensitivity of 95 – 100%
- Disadvantages: - invasive and challenging to perform
- side effects of contrast
- contraindications: - stones in oral portion of Wharton's duct
- active infection
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CT scan-
MRI
-can miss 2-mm to 3-mm calculi that cause no ductal dilatation
MR sialography of SMG duct with evoked salivation - accuracy similar to Digital Sialography & superior to U/S
Sialendoscopy
-Can identify stenoses that may be associated with both stones.
-Not routinely available in Melbourne
TREATMENT (Overview)
If presents with acute swelling +/- infection the treatment principles are to improve salivary flow and treat the underlying infection.
- Keep well hydrated
-Massage back to front
-Chew sugar-free gum- help salivate and reduce stasis
If there is an impacted stone, this could be removed by direct incision on to the duct or by papillotomy by an ENT surgeon.
More distal stones are difficult to remove intraorally. Also, the SM duct has a close relationship with the lingual nerve proximally. These should be treated either by sialendoscopy or in protracted cases removal of the affected gland. (note endoscopy is not routinely available in Melbourne)