Sialography

Sialography is the imaging of the salivary glands, most commonly the parotid gland. The salivary ducts are conventionally examined fluoroscopically with high sensitivity, though cross-sectional imaging with CT or MR sialography havehas also been described.

Indications

• suspected sialolithiasis or salivary duct obstruction
• suspected sialadenitis: to identify ductal strictures or
• suspected sialectasis in chronic inflammatory disorders and autoimmune diseases

Types of sialography

There are three types:

• conventional/fluoroscopic sialography (with or without digital subtraction)
• CT sialography (ultrafast technique)
• MR sialography

In most cases, ultrasound (with sialography, if neededrequired) is an appropriate imaging pathwaymodality for the investigation of ductal pathology. UltrasoundIn cases of sialolithiasis, ultrasound of the parotid glands is a useful adjunct, readily available, noninvasive, and cheaperinexpensive option, in cases of sialolithiasis.

Procedure

Technique of conventional sialography

• control images are taken with the patient supine to assess for radio-opaque calculi
  • lateral oblique and anteroposterior views
  • using tongue depressors for submandibular
• the patient may be asked to suck on a lemon or secretory stimulant for 2-3 minutes before sialography
  • to make the salivary duct opening conspicuous for cannulation
• symptomatic parotid or submandibular duct cannulated
  • 21 gauge catheter for Stensen's duct
    • located adjacent to the crown of the second upper molar in the buccal mucosa
  • 24 or 27 gauge for Wharton's duct
    • at the base of the frenulum of the tongue
• up to 2 mL of water soluble-soluble contrast is instilled
• care should be taken not to introduce air into the salivary ducts
  • , as it can simulatemimic a ductal calculus
  on sialography

Advantages

• higher spatial resolution for superior diagnostic elucidation ( when(when the procedure is successfully achieved) with accurate delineation of second- and third order-order branches.
• enables therapeutic approach in sialoendoscopy for removal of sialithssialoliths, retrograde displacement of sialithssialoliths to relieve acute obstruction, and to dilate strictures.

Disadvantages

• invasive procedure
• substantial failure rate of procedure (especially submandibular sialography) due to cannulation problems, lack of skill, lack of patient compliance, pain, etc
• radiation exposure
• contrast media exposure with risk of allergic reaction.

Technique of CT sialography

The procedure is essentially the same as a conventional sialogram, after which the patient is positioned in a CT in neutral supine position and multiplanar. Multiplanar data acquisition allows for 3D reconstruction. Also intravenousIntravenous contrast material can be administered for better soft tissue assessmentevaluation, especially for parotid masses. In the 1970s and 80s1980s, when this technique was first introduced, slower CT scans called for delayed ductal emptying, for which atropine was given.

Advantages

• assessementassessment of glands other glandsthan the parotids is possible
• better diagnosis of parenchymal pathology, excellent visualisation of the deep lobe, and better substractionsubtraction options
• no special positioning required

Disadvantages

• intravenous atropine is required to minimise run-off of contrast and impair ductal clearance, in some cases
• radiation exposure
• invasive procedure

Technique of MR sialography

MRI sialography is a fairly sensitive and reliable method of evaluating the salivary glands. Fast acquisition heavyheavily T2 weighted sequences (e.g. RARE, CISS, FISP, as used in MRCP and MR urography) brighten intraluminal fluid and display ductal morphology adequately with no requirementneed to inject contrast ininto the ducts. MR contrast administered intravenously is a useful adjunct.

Advantages

• rapid acquistionacquisition
• non-invasive
• assessementassessment of other glands possible
• excellent delineation of parenchymal pathology
• no special positioning required
• because no cannulation is required, the risk of airbubblesair bubbles simulating intraductal calculi is minimised

Disadvantages

• general MRI contraindications, e.g. pacemakers, implants, claustophobia claustrophobia
• dental fillings, implants, bridges, etc can cause image impairment
• only first- and second order-order branches can be delineated.

See also

• sialolithiasis
• sialadenitis
• sialectasis