Salivary gland stones, medically termed sialoliths, are calcified masses that develop within the salivary glands or their ducts, obstructing the normal flow of saliva into the mouth. This condition, known as sialolithiasis, is the most frequent cause of swelling and pain in the major salivary glands. Sialoliths are mineral concretions, usually composed of calcium phosphate and hydroxyapatite. Understanding this condition involves recognizing its appearance, symptoms, and the medical approaches used to manage this common oral health concern.
Anatomy and Formation of Sialoliths
The human mouth contains three pairs of major salivary glands: the parotid, submandibular, and sublingual glands. Sialoliths occur most frequently (80% to 90% of cases) in the submandibular gland and its duct (Wharton’s duct). This prevalence is due to the duct’s long, upward flow path, which promotes salivary stagnation. The submandibular gland also produces thicker saliva that is naturally richer in calcium, further increasing the risk of stone formation.
Stone formation begins when mineral salts precipitate around a central organic core, or nidus, such as mucus or dead cells, retained within the ductal system. Calcium salts deposit in concentric layers, slowly building a calcified mass that can range from a few millimeters to several centimeters in size. Factors that reduce the production or flow of saliva, such as dehydration, certain medications, and smoking, increase the concentration of minerals, making stone formation more likely.
Identifying the Signs of a Blockage
The presence of a stone often goes unnoticed until it grows large enough to cause an obstruction. The classic sign is the sudden, intermittent experience of swelling and pain in the affected area, often felt under the jaw, beneath the tongue, or in the cheek.
The pain and swelling typically intensify just before or during mealtimes, a phenomenon known as “mealtime syndrome” or “salivary colic.” This occurs because food stimulation increases saliva production, but the stone prevents the saliva from draining into the mouth. The resulting back-up of saliva creates pressure, leading to throbbing pain that usually subsides within an hour or two as saliva production slows down. If the blockage is near the duct’s opening, a person might be able to feel a small, hard lump beneath the mucosa. Prolonged obstruction can lead to a secondary bacterial infection, characterized by redness, fever, and sometimes a foul taste from pus discharging into the mouth.
Medical Confirmation Through Imaging
Because sialoliths can be difficult to locate through a simple physical examination, medical professionals rely on specialized imaging to visualize the stone. Imaging confirms the stone’s size, location, and number, which directly guides the treatment plan.
Ultrasound is often the preferred initial diagnostic method because it is non-invasive, widely available, and does not use radiation. Ultrasound provides excellent visualization of soft tissues and easily detects stones, especially in the submandibular gland, while also showing any duct dilation.
Conventional X-rays can also be used to identify stones. However, their effectiveness is limited because up to 20% of submandibular stones may not be sufficiently calcified to appear opaque. For complex cases, deep stones, or suspected infection, a Computed Tomography (CT) scan offers superior sensitivity for detecting small or multiple calcifications.
A highly specialized technique is sialendoscopy, which involves inserting a tiny, flexible camera directly into the salivary duct. This provides clear visual confirmation of the stone and is often the definitive diagnostic tool, as it allows for direct visualization and immediate removal.
Approaches to Removal and Management
Management of salivary gland stones begins with conservative, non-invasive strategies aimed at encouraging the stone to pass naturally. Patients are advised to increase fluid intake for adequate hydration, which helps maintain a less concentrated salivary flow. Stimulating saliva production using sialogogues, such as sour candies or lemon drops, helps flush the duct with increased saliva volume. Gentle massage of the affected gland and applying moist heat can also help manually manipulate small stones out of the duct’s opening.
When conservative measures fail, or the stone is too large, interventional procedures become necessary. Sialendoscopy is a minimally invasive option that can both diagnose and treat the condition. Using the miniature endoscope, the doctor can directly grasp and remove smaller stones (typically less than 4 millimeters) using a wire basket or forceps. For larger or deeper stones, a combined approach, such as endoscopic-assisted transoral surgery, may be used, involving a small incision in the mouth. In rare cases of very large, recurrent stones or significant gland damage, surgical removal of the entire affected salivary gland is the last resort.