What are salivary stones?
Salivary stones, also known as salivary calculi, are stones that form in the salivary glands and can develop in one or more of the glands. The stones are made from crystallised forms of substances present in the saliva. They are most common in people over the age of 40 but they can affect people of all ages. Salivary stones can sometimes block the salivary ducts causing the mouth to become dry.
About the salivary glands
Salivary glands are responsible for producing saliva which keeps the mouth moist and enables the breakdown of food. There three pair of salivary glands are known as the sublingual glands, parotid glands and the submandibular glands. Saliva is produced on a constant basis and production usually increases when you eat.
What causes salivary stones?
It is not fully understood what causes salivary stones to develop. Most stones are made from calcium but they are not associated with abnormal levels of calcium in the blood. There is usually no connection between salivary stones and other health conditions. Salivary stones vary in size from 1mm to 3 cm and around 90 percent of stones are less than 10mm in diameter.
Where do salivary stones form?
Most salivary stones develop in the submandibular glands situated underneath the mouth floor. It is rare for salivary stones to develop in the parotid glands, as these glands make saliva that is much thinner than the saliva produced by the submandibular glands, or the sublingual glands.
What are the symptoms of salivary stones?
If the salivary stone is blocking the duct this causes saliva to back up inside the gland and contributes to swelling and pain. Symptoms are usually most common after eating because saliva is unable to exit the gland. Pain is often sudden and intense and tends to wear off around 1-2 hours after eating.
If the duct is not completely blocked (this relates to most cases) the flow of saliva is only partially blocked and symptoms may include:
- Sporadic dull pain centred on the affected gland
- Swelling, which may be persistent or intermittent
- Infection that may cause redness, pain and an abscess to form, resulting in unpleasant symptoms and makes you feel unwell
It is possible for salivary stones to cause no symptoms and the stone is often detected during X-rays for other conditions.
How are salivary stones diagnosed?
In most cases, doctors are fairly certain of the diagnosis based on the symptoms alone and around 80 percent of cases can be confirmed by means of an X-ray. In around 20 percent of cases the stones may not be visible on the X-ray and further tests are required. Additional tests may include:
- MRI (magnetic resonance imaging) scan
- CT (computerised tomography) scan
- Ultrasound scan
- Sialography: this is a special form of X-ray which shows the glands and ducts in detail
- Sialendoscopy: this involves passing a thin tube fitted with a light source into the salivary duct, allowing doctors to see inside the duct and gland to check for the presence of stones
Treatment for salivary stones
Treatment is advised for stones that cause unpleasant symptoms, including the removal of the stones, gentle probing by a doctor or therapeutic sialendoscopy.
Sometimes gently probing the stone can knock it loose into the mouth and it can then be removed by a doctor using a fine, blunt instrument.
A fine tube fitted with a light and tiny camera is inserted into the salivary duct. If the camera picks up a stone the grabbing attachment of the tube is used to capture the stone. This is a successful procedure in 17 out of 20 cases and is carried out under local anaesthetic to prevent pain.
Surgery involves a small operation to remove the stone, but it is less common thanks to the introduction of therapeutic sialendoscopy.
Once a stone has been removed it is unlikely that more stones will develop in the future.