Investigation of salivary gland disease

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CHAPTER 6 Investigation of salivary gland disease

Vivian E. Rushton

Contents

Introduction
Sialography

image Indications/contraindications
Complementary and competing investigations

image Ultrasonography
image Computed tomography (CT)
image Magnetic resonance (MR)
image Radioisotope imaging (sialoscintigraphy)
image Conclusion
Preoperative assessment of the patient and room preparation
Plain intraoral films for identifying calcified sialoliths
The basic equipment to perform sialography
The standard procedure
Variation of the standard technique

image Hydrostatic sialography
image Subtraction radiography
image Basket retrieval of mobile calculi
image Balloon dilatation of strictures
Aftercare
Image interpretation

image Obstructive sialadenitis
image Autoimmune sialadenitis
image Trauma and post-trauma evaluation
image Presence of tumor
References
Further reading

Introduction

Salivary gland tissue has been shown to display a wide diversity of pathology encompassing inflammatory, obstructive, infectious, neoplastic and systemic disease. Inflammatory and obstructive disease within salivary gland tissue accounts for the majority of patients seeking treatment for their symptoms whereas the incidence of salivary gland tumors is extremely low.

This pathology division is reflected in the radiological techniques employed when imaging patients with salivary gland disease. For those patients presenting with inflammatory disease, plain film radiography, either alone or in combination with contrast studies and/or ultrasonography, often comprises ‘first-line’ imaging. These techniques provide the high resolution images with which to detail the presence of salivary calculi and allow the clinician to document accurately any significant changes within the ductal architecture of the gland. For those patients in whom a mass lesion is suspected then computed tomography (CT) and magnetic resonance imaging (MRI) are the imaging modalities of choice.

The presenting symptoms of the patient are often very useful in determining the type of abnormality present. Typical symptoms of inflammatory disease are swelling of the salivary gland allied with mealtimes and the sight and smell of food followed by a gradual reduction of the swelling having eaten. The latter is highly suggestive of either obstruction by a calculus or an inflammatory induced ductal stricture which indirectly compromises salivary flow. In some cases, the patient may additionally complain of pain, a bad taste and pus may or may not be evident at the duct orifice. These symptoms and signs are indicative of current inflammatory disease. Finally, a number of patients may present with a dry mouth, the causes of which are wide ranging.

The aim of this chapter is to provide details of the most common radiographic techniques with which to image salivary gland pathology, whilst also providing the reader with an overview of each of the other competing investigations and the rationale for their use.

Sialography

The technique employs the use of contrast media to delineate the fine anatomy of the salivary gland ductal system. Patient symptoms will range from pain, which may be acute or chronic in its presentation, to a generalized recurrent or discrete swelling which is often present at mealtimes. Some patients are referred with a dry mouth which relates to a myriad of clinical conditions including autoimmune diseases, drug therapy and previous radiotherapy.

Indications

• Possible obstruction within the salivary duct system. Sialography should only be carried out after a plain radiographic examination to exclude or confirm the presence of either calcified or non-calcified sialoliths (i.e. calculi) or the presence of foreign bodies
• An evaluation of the extent of irreversible ductal damage
• To enable the differentiation between a variety of disease entities, i.e. chronic sialadenitis, Sjögren’s disease, sialosis etc
• An evaluation of fistulae, ductal trauma and ductal strictures

Contraindications

• A calculus close to the duct orifice
• Sialography should not be performed if the salivary gland is infected
• Sialography is best avoided in cases of known iodine hypersensitivity

The presence of an acute inflammatory episode would be confirmed clinically by the presence of pain and swelling of the salivary gland. Similarly, a chronically inflected salivary gland with pus emanating from the salivary duct orifice would also contraindicate sialography until the infection had been controlled by appropriate antibiotic therapy.

Complementary and competing investigations

Ultrasonography

Newer ultrasound equipment exhibits high spatial resolution. This factor, combined with the relative superficial anatomical position of the salivary gland tissue relative to the ultrasound probe, allows the operator to obtain high definition images. Similarly, the superficial topography of the salivary gland tissue also permits fine-needle aspiration biopsy and core biopsy techniques to be performed with relative ease for both the patient and the operator (Bialek et al., 2006).

The technique has become commonplace in clinical practice when assessing generalized swellings or the presence of a mass within the salivary glands.

Advantages of the technique

• Non-invasive
• Does not involve the use of ionizing radiation
• Can differentiate between intra- and extra-glandular lesions
• Use of color Doppler enables identification of vessels
• More sensitive than CT in identifying small lesions
• Can identify calculi >2 mm
• Enables fine-needle aspiration biopsy of lesions to be undertaken (Bradley, 1993)

Disadvantages of the technique

• Difficulties encountered in identifying lesions confined primarily to the deep lobe of the parotid gland
• Margins of deep lobe lesions may be difficult to identify in their entirety. Needs additional investigation using CT and/or MRI to evaluate fully the extent of the lesion

Computed tomography (CT)

The technique can be used to diagnose swellings both associated with the salivary glands themselves and those structures extrinsic to the glands.

Advantages of the technique

• Allows three-dimensional imaging
• Allows the identification of calcified sialoliths
• Enables the clinician to determine the extent of the disease
• Allows differentiation between cellulitis and abscess formation
• Allows differentiation between pathology in particular compartments in the suprahyoid neck, i.e. between the parotid and masticator space
• Determines the nature of the margins and the content of the lesion
• Determines whether the lesion is intra- or extra-capsular
• Has high sensitivity for the detection of salivary gland tumors
• CT sialography allows better delineation of the major duct architecture
• IV contrast highlights pathology

Disadvantages of the technique

• Fine anatomy of intra-glandular ducts is not well imaged
• Provides no information on salivary gland function
• Stenson’s duct seen only if markedly dilated
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