Sialadenitis

Imaging of

parotid anomalies in infants and children. Juvenile recurrent parotitis. Multiple foci of salivary secretions scattered in a normal sized gland, with some central calcification [white arrow] and without Stensen’s duct dilatation, on ultrasonography (a and b), axial fat sat T2-weighted image (c) and MR-sialography (d)

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Imaging of

the sublingual and submandibular spaces. Sialolithiasis with resultant sialadenitis. Axial contrast-enhanced CT images at the level of the submandibular gland demonstrate two well-circumscribed calcifications in the distal right submandibular duct (a, arrow). The right submandibular duct is dilated proximal to the stones (b, arrowhead). There is enlargement and enhancement of the right submandibular gland (*) compared to the normal left submandibular gland

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Sialadenitis refers to inflammation of the salivary glands. It may be acute or chronic and has a broad range of causes.

Clinical presentation

Patients may present with painful swelling of the concerned salivary gland, after eating (salivary colic). In bacterial sialadenitis, there may be a purulent discharge.

Pathology

Etiology

Sialadenitis can occur in various forms ranging from acute bacterial sialadenitis (acute suppurative sialadenitis) to acute viral sialadenitis to chronic sialadenitis.

Acute sialadenitis is most commonly caused by an ascending bacterial infection, with Staphylococcus aureus or Streptococcus viridans being the most common organisms . Sialolithiasis is often present (causing obstructive sialadenitis) and stones are found in ~85% of submandibular ducts and ~15% of parotid ducts . Other causes of acute sialadenitis include dehydration, immunosuppression, iatrogenic (drug-induced) and rarely haematogenous spread . Rarely sialadenitis may be secondary to an obstructive salivary duct carcinoma.

Epidemic parotitis is associated with the mumps virus, occurs mostly in children and is usually bilateral .

Associations

Other conditions related to sialadenitis include:

Sjogren syndrome: chronic sialadenitis
Mikulicz syndrome: chronic sialadenitis
post-radiation: post-irradiative sialadenitis
iodine-131 administration
HIV-associated sialadenitis or immune reconstitution inflammatory syndrome (IRIS), often presenting with bilateral parotid swelling .

Distribution

Due to calculi being a dominant etiological factor, the distribution of sialadenitis follows that of sialolithiasis and therefore the submandibular glands are the most commonly affected (approximately 85%) as the submandibular ducts have more of an upward course and the secreted saliva has a higher viscosity .

Radiographic features

Fluoroscopy

Sialography is contraindicated in acute sialadenitis because it can worsen the infection .

Ultrasound

In acute sialadenitis, the affected gland appears enlarged, hypoechoic and hyperemic on ultrasound .

In chronic infective forms, the affected gland appears atrophic and diffusely hypoechoic with irregular margins - the ultrasound appearances have been likened to that of a “cirrhotic” liver .

There may be evidence of sialectasis if recurrent.

CT

Acute sialadenitis:

enlarged salivary gland with abnormal attenuation, indistinct margin and vivid contrast enhancement with associated adjacent fat stranding and/or thickening of the deep cervical fasciathat is typically unilateral
dilated duct from sialolithiasis or stenosis
enlarged intra- or extra-glandular lymph nodes may also be seen but this is non-specific and can occur in other conditions such as malignancy
abscesses are hypodense fluid collections, which may or may not be loculated

MRI

The salivary gland(s) is often enlarged. The affected gland can range from well-defined to poorly defined. Signal characteristics in the majority of cases tend to be heterogeneous .

Signal characteristics include:

T1
- acute sialadenitis: low signal
- chronic sialadenitis: inhomogeneous low signal
T2
- acute sialadenitis: overall signal tends to be high
- chronic sialadenitis: overall signal may be low-to-intermediate due to fibrosis

Treatment and prognosis

Treatment is usually endoscopic or surgical stone removal . If stone removal is unsuccessful the duct and gland may need to be removed if symptoms do not resolve.

Differential diagnosis

Differential conditions to keep in mind include :