Family doctor

Overview

• There are three main salivary glands in the head and neck and hundreds of tiny ones. Stones usually occur in the submandibular glands, less frequently in the parotid gland and very rarely in the sublingual and minor salivary glands.
• Stones form from mineral deposits in the gland ducts, causing swelling and pain and sometimes becoming infected.
• Diagnosis is by x-ray, ultrasound or injection of dye into the affected gland. Treatment methods range from prevention by massage and changes to lifestyle, through to removal of the stone or gland.

What are salivary glands and stones?

Salivary glands produce saliva in response to food being placed in the mouth. Even the thought or smell of food can stimulate salivary flow and most people make about one litre of saliva per day. As well being 99.5% water, saliva has minerals and proteins that aid digestion and keep the mouth and teeth healthy.Salivary Stones known as Calculi, form within the salivary glands or ducts.

Where are the salivary glands?

There are three main paired glands in the head and neck producing saliva. They are the:

• parotid glands
• submandibular glands
• sublingual glands

The parotid glands are the largest and overlie the angle of the jaw in front of the ear. A tube, known as Stensens duct, drains saliva from the glands into the mouth. The openings are inside the cheek opposite the upper molar teeth.

The submandibular glands lie deep to the horizontal part of the lower jaw. Their ducts are the longest and narrowest of all the salivary glands, and enter the mouth under the front of the tongue.

The sublingual glands lie deep in the lining of the mouth on each side of the tongue. These glands have many short ducts entering the mouth directly through the mouth lining.

In addition to these major glands there are hundreds of minor salivary glands throughout the lining of the mouth and throat, with most on the lips and soft palate.

How do salivary stones form?

Stones usually form in response to poor salivary flow. Good flow washes debris out, but with poor flow debris becomes a place for minerals to attach to. In over 90% of cases this occurs in the submandibular gland, probably because of the shape and length of the duct and the chemical makeup of its saliva. The parotid gland is next most commonly affected (6% of cases), whereas the sublingual and minor salivary glands are only rarely affected.

What are the symptoms of a salivary stone?

Stones in the affected gland or duct cause obstruction to the flow of saliva, resulting in swelling of the gland. The swelling can be painful and usually occurs during eating or when thinking about food. It usually settles slowly after finishing a meal and can be aided by massaging the gland, which will feel firm and be tender.

Sometimes the swelling remains and occasionally the gland can become infected and abscessed resulting in fever, severe pain and inflammation in the overlying skin.

How are stones diagnosed?

The majority (80%) of these stones are visible on plain x-ray, however some are not seen on x-ray so are investigated using ultrasound or a sialogram: 

An ultrasound scan is a painless procedure using high frequency echoes where the gland and duct can be identified by probe. Stones may be seen as shadows within the gland or duct.

A sialogram involves using a dye injected through the mouth into the duct opening. The dye passes back up the duct into the gland. An x-ray is then taken showing where the dye fills the duct and gland. Stones are seen as "holes" in the dye. This procedure can sometimes cause discomfort.

It is possible to have more than one salivary stone or a group of them. Sometimes one stone is not seen, however "sludge" (multiple small stones) is present in the duct system.

In some cases no stones are seen but the sialogram shows a stricture (narrowing) of the duct. Strictures usually result from previous stones which may have passed out of the duct spontaneously, leaving a scar.

What is the treatment for salivary stones?

Stones in the submandibular duct can usually be removed under local anaesthetic. A cut is made in the floor of the mouth and the duct opened. Sometimes a stitch is placed in the floor of mouth first, to stop the stone(s) slipping back up the duct.

If the stone is further back in the submandibular gland itself, the gland usually needs to be removed. This is done through an external cut on the neck 2- 3cm below the jawline. During this procedure a nerve called the marginal mandibular nerve is at risk of being cut or stretched, and occasionally there can be some weakness in the lower lip. If this occurs it is usually temporary.

Stones in the distal parotid duct are dealt with by either dilating or opening the duct from inside the mouth, or by making a cut over the stone through the cheek skin, just below the cheekbone. Repeated problems with the parotid gland, or stones within the gland itself occasionally lead to removal of the gland. This procedure involves an S-shaped incision passing in front of the ear, around behind the ear lobe and then down into the neck.

How can stones be prevented?

If swellings are caused by sludging or stricture and there are no particular stones, the problem can be helped by dilating (stretching) the duct opening, regular massage of the gland, drinking plenty of fluids, improving dental hygiene and quitting smoking.