Salivary gland infections

Salivary gland pathology will present in the primary care setting and is relatively common. The major salivary glands are parotid, submandibular and sublingual glands. Note there are also minor salivary glands on the mucosa of the lips, tongue and pharynx.
Generally, any diseases of the salivary glands will result in the patient complaining of swelling, pain or dry mouth. With regards to the anatomy of salivary glands, as there are nervous structures traversing them, salivary gland pathology may result in paraesthesia or nerve weakness if there is nerve involvement.

The most common diseases involving salivary glands are:
1) Infections resulting in sialadenitis
2) Obstructions – sialolithiasis, stenosis or strictures of the ducts
3) Inflammation due to autoimmune conditions
4) Salivary gland tumours [1][2]

Figure 1. Anatomy of salivary glands [3]

Infections

Ascending sialadenitis

A single gland or multiple glands can be infected; the parotid gland is commonly affected. The prevailing aetiology is ascending infection arising due to bacterial contamination of the duct and therefore the gland in a retrograde fashion. The offending organisms are S.aureus, streptococcal species and Haemophilus influenza. Patients who have existing medical conditions or post-operative patients may be more at risk of this [1].

Clinical features
1) Acute onset pain and swelling often after eating (meal time symptoms)
2) Oedema
3) Enlarged and tender gland
4) Overlying skin is erythematous
5) Pus discharging from duct orifice
Treatment
2) Encourage patients to drink lots of water
3) Natural sialagogues e.g. lemon
4) Massage affected gland
5) Broad spectrum antibiotics e.g. co-amoxiclav (check with local trust protocol)
6) Ultrasound may be required to investigate any underlying salivary gland pathology especially in recurrent cases
7) Follow-up in outpatient clinic based on trust protocol
7) In those with underlying medical conditions, optimisation by the GP may be indicated e.g. improved diabetic control

Figure 2. Pus observed from parotid duct [4]

Note on occasion these patients can become systemically unwell and may develop an abscess which requires incision and drainage of the abscess under GA. If this occurs, the principles of treatment are similar to how you would manage a severe orofacial infection. This requires a discussion with your seniors.

Mumps

If multiple glands are affected this is likely to be viral in nature e.g. mumps due to paramyxovirus. Mumps has been reported to be the most common cause of non-suppurative sialadenitis therefore especially in the younger patient this should always be considered as part of your differentials. You should enquire as to vaccination status specifically MMR vaccine. Diagnosis is by viral serology centered on identifying salivary mumps IgM [2]. It is important to identify if mumps is the underlying condition as management varies and it is a notifiable disease.

Clinical features
1) Parotitis – localized pain and oedema
2) Otalgia
3) Fever
4) Systemic upset
5) Pain on eating
Treatment
1) Hydration
2) Pain control
3) Massage swollen glands
4) General supportive measures

HIV

Manifestations involving salivary glands can include bilateral swelling of the parotid glands, dry mouth and may precede a confirmed diagnosis of HIV.
This is formally referred to as diffuse infiltrative lymphocytosis syndrome (DILS). Clinically it will present with enlargement of the glands and xerostomia. There may also be neural involvement due to the intimate relationship between the facial nerve and the parotid gland presenting as facial palsy. Ultrasound imaging is recommended [6]. If suspected, formal HIV testing is required after discussion with the patient.

Obstructions

Obstruction most commonly affects the submandibular gland followed by the parotid gland. Infection almost always follows on from obstruction. Obstruction can generally be categorised as secondarily due to salivary calculi (also known as stones/sialolith) or duct strictures.
Sialoliths can increase in size over time, and during periods of dehydration it is widely thought they deposit themselves within the duct architecture and grow further in size. However once they get to the point where they can obstruct the duct, saliva starts to get trapped and this builds up within the ductal and gland architecture.
The result is swelling of the gland and persistent obstruction which increases the likelihood of an infection presenting similarly to sialadenitis. Subsequently patients experience what is referred to as "meal time syndrome" in which the thought of food stimulates salivary flow however due to the inability to express saliva through the ducts, saliva pools and causes swelling/pain.
A stricture is a narrowing of the duct which results in decreased salivary flow. As a result, the lack of salivary flow causes it to build up within the gland causing swelling. The literature suggests this is more common in the parotid gland rather than the submandibular gland [1][2].

Figure 4. Stone within sublingual duct [7]

Figure 5. Stricture point within Stenson's duct [8]

Tips for examining these patients
1) Is there eversion of the earlobe? (Indicative of a parotid swelling)
2) Swelling underneath the angle (parotid) and body of mandible (submandibular)
3) Inflammation around duct orifice intra-orally or evidence of protruding stone
4) Massage the gland to determine if there is salivary flow or pus from duct orifice
5) Palpate the cheek or along the path of the duct – sialoliths large enough may be palpable
Investigations
1) Ultrasound
2) Lower occlusal - can demonstrate sialoliths in the submandibular gland
3) Sialogram
4) CT/MRI
Management
Conservative management is preferred due to proximity of vital structures and nerves to commonly affected glands. Surgical management involves removal of the stone or the entire gland. However removing the gland is problematic as there is a risk of damage to the marginal mandibular, lingual and facial nerve.
Surgical management involves open or closed procedures. There is scope for surgical management under LA which involves removing a sialolith or dilating a narrowed duct. Techniques involve “Dormia baskets (for grasping and extracting stones), balloon catheters (for dilating strictures) and salivary endoscopes (for visualising and irrigating the duct system, dilating strictures and directing stone removal [2].”

Inflammation

Some autoimmune conditions have salivary gland involvement such as Sjogrens, IgG4 disease, sarcoidosis.
Sjogrens for example is an autoimmune condition in which there is lymphocytic infiltration of the exocrine glands, mainly the salivary and lacrimal glands. The result is reduced salivary flow and tear production and there may be accompanying salivary gland enlargement [2].

Mucocoeles and ranula’s

Mucocoeles are manifestations of obstructions of minor salivary glands. They appear as a blister with clear fluid. They are not known to be painful but can irritate patients depending on their location. Patients may often catch the mucocoele with their teeth further traumatizing it and causing swelling. They can recur from time to time and can be surgically excised under LA on an outpatient basis.
A ranula is an extravasation cyst – a collection of saliva beneath the mucosa. They are larger in terms of the observable swelling and can have a blue tinge. There is often a history of trauma in the area. Traditionally, the treatment is excision of the sublingual gland on the affected site. However, there are a range of treatments available such as marsupialization.

Figure 6. Clinical image of a Ranula [9]

Salivary gland tumours

The highest prevalence of salivary tumours in terms of location is parotid > submandibular > minor salivary glands. However the incidence of malignancy increases in the smaller salivary glands.
It can be difficult to distinguish between what may be a benign or malignant tumour based on presentation. Benign tumours tend to slowly grow over time and are painless. Conversely clinical signs such as pain, facial palsy or paraesthesia should be red flags.
Special investigations that are usually called upon are US guided FNA, ultrasound, MRI and CT [1][2].

Pleomorphic adenoma

This is the most common salivary tumour and occurs most of the time within the superficial portion of the parotid gland.
It generally feels firm and is mobile. Recommended treatment is surgical removal however thorough surgical planning is required pre-operatively. An US guided FNA is performed and the proximity of the facial nerve to the tissues needs to be investigated [1][2].

Warthin's tumour

Typically presents in the tail of the parotid gland in men > 50 years old. It is the second most common salivary tumour. Documented associations are with smoking and irradiation. This tumour commonly presents as an asymptomatic, slow growing and on palpation can feel mobile and rubbery [1][2].
Treatment modality of choice is a partial parotidectomy.

Other malignant tumours

As mentioned previously, malignant tumours are more likely to be found in the smaller glands. They tend to have epithelial origins and present as a hard, fixed mass.
Mucoepidermoid carcinomas are the most common malignancy in the parotid gland and minor salivary glands; these are often found in the palate.
Adenoid cystic tumours are more commonly found in the submandibular gland. They are slow-growing and are notorious for perineural spread.
Sublingual tumours can present in a variety of ways such has hard masses with overlying ulceration and/or obstruction of the duct [1][2].

If in doubt after your examination or if something looks suspicious, do not hesitate to involve a senior.

When to escalate

1) Cellulitis
2) Sepsis
3) Inadequate intake
4) Spreading infection - think of your cervicofascial spaces
5) Facial palsy
6) Repeated salivary gland infections

References

[1] Brown J. Salivary gland diseases: Presentation and investigation. Prim Dent J [Internet]. 2018;7(1):48-57. Available from: https://journals.sagepub.com/doi/pdf/10.1308/205016818822610280
[2] Wilson K, Meier J, Ward P. Salivary Gland Disorders [Internet]. Aafp.org. 2020 [cited 14 June 2020]. Available from: https://www.aafp.org/afp/2014/0601/p882.html
[3] Salivary Glands and Radiographic Examination [Internet]. Radtechonduty.com. 2020. Available from: http://www.radtechonduty.com/2014/04/salivary-glands-and-radiographic-examination.html
[4] Jadhav, S., Jadhav, A., Thopte, S., Marathe, S., Vhathakar, P., Chivte, P., & Jamkhande, A. (2015). Sjögren's Syndrome: A Case Study. Journal of international oral health : JIOH, 7(3), 72–74.
[5] Image from: https://pancreas.imedpub.com/acute-pancreatitis-from-mumps-reinfection-in-adulthood-case-report.php (Web page unavailable)
[6] Abdurakhmanov A, Zandman-Goddard G. HIV Spectrum and Autoimmune Diseases. Infection and Autoimmunity. 2015;:371-392.
[7] Image from: http://www.srmjrds.in/article.asp?issn=0976-433X;year=2015;volume=6;issue=1;spage=69;epage=72;aulast=Kasat;type=3 (Web Page unavailable)
[8] Salivary Gland Strictures - Professor Mark McGurk [Internet]. Salivary-gland.co.uk. 2020. Available from: http://www.salivary-gland.co.uk/salstrictures.htm
[9] Ranula - The Medical Notes [Internet]. The Medical Notes. 2020. Available from: https://www.themedicalnotes.com/surgery/general-surgery/ranula/