What is the workup for a suspected salivary gland stone?

Workup of Salivary Gland Stones

The initial diagnostic imaging of choice for suspected salivary gland stones should be ultrasound, followed by CT with intravenous contrast if ultrasound is inconclusive or if there are concerns about deep extension or bone involvement. 1, 2

Initial Diagnostic Approach

Ultrasound

• First-line imaging modality due to:
  • Non-invasive nature
  • No radiation exposure
  • High accessibility and low cost
  • Excellent visualization of superficial structures
  • Ability to detect stones with high sensitivity
  • Can be used to guide fine-needle aspiration if needed 1, 3

Ultrasound is particularly effective for:

• Submandibular gland stones (most common location - 84% of cases) 4
• Superficial lobe of parotid gland 1
• Real-time assessment of gland morphology
• Detection of ductal dilation proximal to obstruction
• Assessment of surrounding inflammatory changes

Limitations of Ultrasound

• Limited visualization of:
  • Deep lobe of parotid gland
  • Sublingual gland
  • Stones in the proximal duct system
  • Subtle ductal abnormalities 1, 3

Second-Line Diagnostic Modalities

CT with IV Contrast

When ultrasound is inconclusive or additional information is needed:

• Superior for detecting small or multiple calcifications
• Better visualization of deep structures
• Excellent for assessing bone involvement
• Can detect stones not visible on conventional radiography 1, 2

MRI with Contrast

Indicated when:

• Soft tissue detail is critical
• Perineural invasion is suspected
• Skull base involvement is a concern
• Patient cannot tolerate CT contrast 1

MRI with diffusion-weighted sequences provides better tissue characterization and can help distinguish between inflammatory and neoplastic processes 1.

Sialography

• Traditional gold standard for ductal anatomy visualization
• Digital subtraction sialography shows exact stone location and ductal stenoses
• Particularly useful when planning sialoendoscopy
• Contraindicated in acute infection
• Less commonly used now due to invasive nature 2

Advanced Diagnostic Options

Sialoendoscopy

• Both diagnostic and therapeutic
• Direct visualization of ductal system
• Allows for immediate intervention
• Particularly valuable for stones not detected by other imaging modalities
• High success rate when combined with other techniques (90-98%) 5

MR Sialography

• Non-invasive alternative to conventional sialography
• No contrast material required
• Can be performed during acute inflammation
• Evolving technique with improving resolution 2

Diagnostic Algorithm

1. Initial Assessment: Ultrasound of the affected salivary gland
2. If ultrasound is positive: Proceed with treatment planning based on stone size and location
3. If ultrasound is negative or inconclusive:
   • For suspected submandibular or parotid stones with possible bone involvement: CT with IV contrast
   • For suspected deep parotid or sublingual stones: MRI with contrast and diffusion sequences
4. For complex cases or when planning minimally invasive removal: Consider sialography or sialoendoscopy

Clinical Pearls and Pitfalls

• Salivary stones are most common in the submandibular gland (84%) followed by parotid (13%) 4
• Submandibular stones are typically located in Wharton's duct (90%), while parotid stones are often within the gland itself 4
• Multiple imaging modalities may be required for complete assessment
• Always consider the possibility of malignancy, especially in older patients with unilateral swelling
• Negative imaging does not completely exclude small stones, particularly in the minor salivary glands
• The goal of management should be stone removal with preservation of gland function whenever possible 5

By following this diagnostic approach, clinicians can accurately identify salivary stones, determine their exact location, and plan appropriate treatment while minimizing unnecessary radiation exposure or invasive procedures.