The information – submandibular calculi

The patient’s unmet needs (PUNs)

A 40-year-old man attends the emergency surgery complaining of a swelling on his jaw. This has appeared over the last few weeks on and off, mainly when he’s eating, though it’s now taking longer to subside. Examination reveals a diffuse and slightly tender swelling of his right submandibular gland. According to the patient it is often a lot larger. The rest of the examination – including an inspection of the oral cavity – is normal. You explain that you think he has a submandibular duct stone. ‘Why have I got this, what can I do to get rid of it, will I need an operation?’ he asks. ‘And what do I do if the swelling doesn’t go down – it gets very painful?’

The doctor’s educational needs (DENs)

What causes these stones and how common are they?

Post-mortem studies show salivary calculi to be present in 1.2% of the population but that admission with symptoms occurs in only 3,658 patients each year in the UK. Over 90% of salivary calculi occur in the submandibular gland – the remaining occurring in the parotid gland. It is rare for either the sublingual or minor salivary glands to be affected.

Stones have both organic (glycoproteins, mucopolysaccharides and cellular debris) and inorganic components (calcium phosphate and carbonates). Submandibular stones contain more calcium than parotid calculi and therefore are more likely to appear radiopaque.

Most stones occur at the sites of where the duct kinks (submandibular and Parotid glands) – close to the hilum of the submandibular gland – where the duct bends around the free end of the mylohyoid muscle and the anterior border of the masseter muscle, respectively.

It is thought stones form through obstruction of the gland, reduced salivary flow rates, dehydration, changes in salivary pH associated with oropharyngeal sepsis and calcification around foreign bodies, desquamated epithelial cells and microorganisms in the duct.

Do they ever resolve on their own?

If the obstruction of the submandibular duct is related to mucus plugs rather than stones then they can resolve. The incidence of mucus plugs is unknown but if the symptoms are transient and cleared rapidly with no stone on imaging, then it is  likely that mucus plugs are the cause.

Once formed, stones do remain but can be quiescent. They may be released out into the mouth if small enough or may become asymptomatic if the stone drops back into the hilum of the gland.

A chronically inflamed gland may be fibrosed and atrophy to become non-functional and then therefore can remain asymptomatic.

At what point should the patient be referred?

Patients should be referred if the first episode is very severe or if recurrent lower grade symptoms do not resolve after three weeks. Also, if the history is not classical, or if the diagnosis is uncertain, then referral is advised.

Is advice designed to improve the salivary flow likely to make matters worse or better?

This is controversial. One approach is to advise good hydration and analgesia. If the symptoms had been severe then I would avoid using citrus drinks in an attempt to flush it out as this is more likely to cause greater pain.

If you suspect smaller stones, or mucus plugs from past history or on clinical examination and imaging, then sharp tasting drinks are useful. Massaging the gland from posterior to anterior can be helpful, not only to push the calculi forwards but to disperse the accumulated saliva.

Antibiotics are not indicated in acute obstructive episodes as it is a purely mechanical blockage with subsequent inflammation, and not an infection. If symptoms persist over a few days, with pus discharging from the duct, and if the patient is systemically unwell or immunocompromised then oral or intravenous antibiotics are indicated.

What specific advice should the GP give the patient pending definitive treatment?

If symptoms are acute or chronic then advise the patient to keep well hydrated. Analgesia as needed, and they should avoid sharp tasting foods (unless the patient has a history of passing small stones).

If symptoms are subacute then referral to the specialist outpatients department is advisable. Depending on your local services this can be an Oral and Maxillofacial surgeon or an ENT department.

Does increasingly persistent and tender swelling suggest infection? How should the GP treat this?

Yes, if prolonged swelling occurs then start conservative measures and place the patient on co-amoxiclav 625mg tds or clindamycin 300mg qds. An urgent referral to a specialist is also needed.

What action should be taken if the obstruction appears to have become complete, as evidenced by painful, unresolving swelling?

If the acute swelling is persistent and painful then conservative measures as before are advised. Milking the gland regularly is too painful to consider. Small stones may pass spontaneously.

The patients may require admission into hospital for further assessment with imaging if pain and swelling are severe.

How will the oral surgeon manage this problem? How likely is it that the patient will require surgery?

In the acute setting as in this case study, the patient may need admitting for pain relief and rehydration. Gentle palpation of the duct and the gland is essential to identify the position of the stone. If the calculus is palpable and accessible then it is likely that surgery is indicated. Most often the stone, if small, may be close to or at the submandibular duct punctum.

Rarely the patient presents with an abscess infection secondary to obstructive pathology or a suppurative sialadenitis. This will require admission and resuscitation and surgical incision and drainage.

Further investigations are often useful. Commonly a high resolution ultrasound scan performed by a specialised clinician will show an enlarged gland and dilated proximal duct, and a hyper echoic stone with a narrow empty distal duct. During the acute stage a sialogram is relatively contraindicated.

Plain X-ray may show the stones in the submandibular duct or lateral oblique view showing the stones in the gland.

Newer techniques include magnetic resonance sialograms . This is non-invasive, without contrast and shows stones as filling defects with high signal saliva in the ducts and glands.

If possible the stone can be released with a small LA infiltration over the area. An incision over the mucosa and duct will release the stone which, if extruded, allows the proximally blocked saliva to be released and immediate relief from symptoms. At that point milking the gland and citrus drinks can be helpful to flush out the gland. If there are multiple stones then this will help extrude them.

If the stone is proximal, near to or in the hilum of the gland, they can drop back and the symptoms can settle.

Traditionally, if there have been repeated symptoms then the gland and stone can be removed under a general anaesthetic.

With improved techniques and instruments there are radiologically- or endoscopically-assisted stone retrievals from the duct or hilum. A wire basket or forceps can be used to remove it.

Other non-surgical methods have been tried, specifically extracorporeal short wave lithotripsy (ESWL) to break up the stones as in cases of renal calculi, but this is offered only in a few centres. It is mostly used for smaller fixed parotid stones.

Fig.1 - An axial CT scan of the floor of mouth showing a row of six stones along the left submandibular duct

Fig.2 - A sialogram of the left submandibular gland showing dilated ducts(black) and filling defects along the duct to the gland

Mr Mahesh Kumar is a consultant oral and maxillofacial surgeon at Hillingdon, Ealing and Northwick Park Hospitals and =honorary consultant at Charing Cross London.

www.maxillofacialsurgeons.org.uk

Further reading

1. McGurk M, Escudier MP, Brown JE. Modern management of salivary calculi. British Journal of Surgery, 2005; 92 (1): 107-112

2. Katz P, Fritsch MH. Salivary stones: innovative techniques in diagnosis and treatment. Current Opinion in Otolaryngology & Head and Neck Surgery, 2003; 11 (3): 173-178

3. McGurk M, Coombes J. Controversies in the management of salivary gland disease. 2^nd Edition, Oxford University Press.