Initial Diagnostic Approach for Suspected Submandibular Gland Stone
Ultrasound is the first-line imaging modality for evaluating suspected submandibular gland stones, combined with intraoral inspection and bimanual palpation of the duct and gland. 1
Clinical Assessment First
Before any imaging, perform:
- Intraoral inspection to visualize the submandibular duct opening (Wharton's duct) for visible stones or purulent discharge 1
- Bimanual palpation with one finger in the floor of the mouth and the other externally under the jaw to feel for stones along the duct course 1
- Assessment during meals or with sialagogues, as pain typically worsens with eating when stones cause obstruction 2, 3
First-Line Imaging: Ultrasound
Ultrasound should be ordered as the initial imaging study because it is:
- Effective at detecting stones and determining their location 1, 4
- Safe with no radiation exposure 1
- Readily accessible and cost-effective 1
- Capable of showing duct dilation and gland inflammation 4, 5
The submandibular gland is affected in 80-90% of sialolithiasis cases, making this location highly amenable to ultrasound evaluation 2, 4.
When to Add Additional Imaging
Digital subtraction sialography remains valuable when:
- Ultrasound findings are equivocal 4
- Precise duct anatomy is needed for surgical planning, particularly if sialoendoscopy is being considered 4
- Multiple small stones are suspected 4
Non-contrast CT should be considered when:
- Multiple or very small calculi are suspected that ultrasound may miss 4
- The stone location needs precise anatomical definition before surgery 4
What NOT to Order Initially
Open-mouth radiographs (occlusal views) are not recommended as first-line imaging because:
- They have lower sensitivity than ultrasound for stone detection 4
- Up to 20% of submandibular stones may be radiolucent on plain films 4
- They provide limited information about duct anatomy and surrounding soft tissue inflammation 4
MRI is not appropriate for initial stone evaluation, as it is reserved for suspected tumors or complex soft tissue assessment 1
Clinical Pitfall
Most submandibular stones are 5-10 mm in size, but stones >10 mm are considered unusual and warrant documentation 2, 3, 6. The curved course of Wharton's duct and the more mucous nature of submandibular secretions predispose this gland to stone formation 2.