Salivary Stones

Please note that the following is a general guideline only. For a full assessment, exclusion of any other underlying cause for your symptoms and an individualised treatment approach, you will need to be seen by a qualified specialist.

Definition

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

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 of the Stones

SMG-hard stones (more Calcium) , Parotid soft stones (less Calcium)

Initial formation of organic gel, which becomes framework for 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 mouth

-Parotid stones might be noted at orifice of Stensen's duct or along its course

Investigations

US is a good first line investigation. Below is summary of other investigations.

XR

- Intraoral or occlusal views identify radiopaque stones - poor predictive value to do the reasons below

          - false postives-phleboliths, atherosclerosis of lingual artery, calcified cervical LN

           - false negatives-80% parotid stones are radiolucent

US

-Good predicative 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

- Sensitivity of 95 – 100%

- Disadvantages: - invasive and difficult to perform

                         - side effects of contrast 

                        - contraindications: - stones in oral portion of Wharton's duct 

                                                        - active infection

CT scan-accurate

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 obvious 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 intra orally. Also the SM duct has a close relation ship to 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)