The salivary glands

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The salivary glands

Salivary gland disorders

Disorders of the major salivary glands are relatively common, with a large spectrum of underlying diseases. This has led to a variety of classifications. However, the presenting symptoms and complaints allow a broad division into six main categories:

• Acute intermittent generalized swelling of a gland, often related to meals

• Acute generalized swelling of one or more glands

• Chronic generalized swelling, often involving more than one gland

• Discrete swelling within or adjacent to a gland

• Excess salivation.

The important causes of these complaints are summarized in Table 32.1.

Table 32.1

A summary of the main salivary gland complaints and their causes

Salivary gland complaint	Cause
Acute intermittent generalized swelling	Obstructive disorders including: Sialolithiasis – salivary stones Stricture or stenosis of the duct, usually secondary to surgery, stones or infection Recurrent parotitis of childhood

Acute generalized swelling

Infection, either:

Viral, e.g. mumps

Bacterial-ascending sialadenitis

Chronic generalized swelling

Sjögren’s syndrome, either primary or secondary

Chronic infection

Cystic fibrosis

Discrete swelling

Intrinsic tumour, benign or malignant

Extrinsic tumour

Overlying lymph nodes

Dry mouth

Sjögren’s syndrome

Post-radiation damage

Mouth breathing

Functional disorders, including:

Drugs, such as tricyclic antidepressants

Neuroses, particularly chronic anxiety states

Excess salivation

Psychological (false ptyalism)

Reflex, e.g. due to local stimulation

Heavy metal poisoning

Investigations

Several investigations can be used on the salivary glands, the most appropriate often being decided by the patient’s presenting symptoms. The main investigations include:

• Plain radiography

• Sialography

• Magnetic resonance (MR)

• Radioisotope imaging

• Computed tomography (CT)

• Flow rate studies

Plain radiography

The most common disorder of the major salivary glands is obstruction caused either by salivary stones (calculi) or stricture of the ducts. A large proportion of salivary calculi are radiopaque (approximately 40–60% in the parotid and 80% in the submandibular glands) so patients presenting with obstructive symptoms of acute intermittent swelling require routine radiographs to determine the presence and position of the stone(s), as shown in Fig. 32.1.

Fig. 32.1 A Lower 90° occlusal showing a large radiopaque calculus (arrowed) in the right submandibular duct. B Part of a panoramic radiograph showing another calculus (arrowed) in the left submandibular gland. C Rotated AP with the left cheek blown out to ensure the calculus (arrowed) is not superimposed on the underlying bones.

The radiographic projections used commonly for the parotid and submandibular glands are summarized in Table 32.2.

Table 32.2

A summary of the commonly used radiographic projections for the parotid and submandibular glands

Salivary gland	Radiographic projections used
Parotid	Panoramic radiograph Oblique lateral Rotated PA or AP with cheek blown out Intraoral view of the cheek

Submandibular

Panoramic radiograph

Oblique lateral

Lower 90° occlusal (to show the duct)

Lower oblique occlusal (to show the gland)

True lateral skull with the tongue depressed

Rotated AP (below mandible)

Sialography

Sialography can be defined as the radiographic demonstration of the major salivary glands by introducing a radiopaque contrast medium into their ductal system. It is also very effective for the diagnosis of obstruction whether caused by stones or strictures. It is widely used and is probably still the most common specialized salivary gland investigation.

The procedure is divided into three phases.

• The preoperative phase

• The filling phase

• The emptying phase.

Preoperative phase

This involves taking preoperative (scout) radiographs, if not already taken, before the introduction of the contrast medium, for the following reasons:

• To note the position and/or presence of any radiopaque obstruction

• To assess the position of shadows cast by normal anatomical structures that may overlie the gland, such as the hyoid bone

• To assess the exposure factors.

Filling phase

The relevant duct orifice needs to be found clinically, probed and dilated, and then cannulated. This is shown in Fig. 32.2. together with a diagram of the normal anatomy of the major salivary glands and ducts. The contrast medium can then be introduced.

Fig. 32.2 A Diagram showing the normal anatomy of the parotid and submandibular salivary glands, ducts and duct orifices. B Clinical photographs showing these duct orifices (arrowed), being dilated and cannulated.

Three main techniques are available for introducing the contrast medium, as described later. When this is complete, the filling phase radiographs are taken, ideally at least two different views at right angles to one another.

Emptying phase

The cannula is removed and the patient allowed to rinse out. The use of lemon juice at this stage to aid excretion of the contrast medium is often advocated but is seldom necessary. After 1 and 5 minutes, the emptying phase radiographs are taken, usually oblique laterals. These films can be used as a crude assessment of function.

Contrast media used

The types of contrast media (see Ch. 18) suitable for sialography are all iodine-based, and include:

• Ionic aqueous solutions, including:

– Diatrizoate (Urografin^®)

– Metrizoate (Triosil^®)

• Non-ionic aqueous solutions, including:

– Iohexol (Omnipaque^®)

• Oil-based solutions, including:

– Iodized oil, e.g. Lipiodol^® (iodized poppy seed oil)

– Water-insoluble organic iodine compounds, e.g. Pantopaque^®.

Most radiology departments use aqueous solutions. Their relative advantages and disadvantages are summarized in Table 32.3.

Table 32.3

A summary of the advantages and disadvantages of oil-based and aqueous contrast media

Contrast	Advantages	Disadvantages
Oil-based	Densely radiopaque, thus shows good contrast High viscosity, thus slows excretion from the gland

Extravasated contrast may remain in the soft tissues for many months, and may produce a foreign body reaction

High viscosity means considerable pressure needed to introduce the contrast, calculi may be forced down the main duct

Aqueous

Low viscosity, thus easily introduced

Easily and rapidly removed from the gland

Easily absorbed and excreted if extravasated

Less radiopaque, less easy to see in fine ducts

Excretion from the gland is very rapid unless used in a closed system

Note: Since the contrast medium is not being introduced into the bloodstream, there is no need to use the safer, but more expensive, non-ionic contrast media discussed in Chapter 18.

Main indications

The main clinical indications for sialography include:

• To determine the presence and/or position of calculi or other blockages, whatever their radiodensity

• To assess the extent of ductal and glandular destruction secondary to an obstruction

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