Sialolithiasis, commonly known as salivary gland stones, is a condition where calcified masses form within the salivary glands or their draining ducts, obstructing the flow of saliva into the mouth. These blockages, called calculi, are most frequently found in the submandibular glands, located beneath the jaw, accounting for 80% to 90% of all cases. Though less common, stones can also develop in the parotid glands near the ears or the sublingual glands under the tongue. The formation of these hard deposits is the most frequent cause of inflammatory salivary gland disease.
The Mechanism of Stone Formation
The physical process of stone formation begins with saliva, which is naturally rich in mineral salts, primarily calcium phosphate and hydroxyapatite. For a stone to form, the saliva must become supersaturated, meaning the concentration of these salts exceeds their ability to remain dissolved. This saturation makes crystallization possible.
The actual formation of the stone, called a sialolith, requires a microscopic core or nidus. This core often consists of organic debris, such as shed epithelial cells, thickened mucus, or bacteria. Once a nidus is established, mineral deposits begin to precipitate and layer onto this structure.
The stone grows through a slow, intermittent process of mineral deposition, resulting in a calcified mass with concentric layers. An increase in the alkalinity (higher pH) of saliva decreases the solubility of calcium salts, encouraging crystallization. Stones can vary widely in size, from less than one millimeter to several centimeters.
Primary Contributing Factors
Conditions that lead to stagnation or concentration of saliva are the primary factors encouraging stone formation. Dehydration is a common cause because low fluid intake reduces the salivary flow rate and increases the concentration of mineral salts. This concentrated fluid is more prone to reaching the supersaturation levels required for crystallization.
Certain medications can significantly reduce saliva production, a condition called xerostomia or dry mouth, which is a major risk factor. Drugs with anticholinergic effects, such as some antihistamines, antidepressants, and medications for bladder control, decrease salivary flow and increase stone risk. Diuretics and some blood pressure medications also contribute by causing fluid loss, leading to dehydration.
Reduced salivary flow from other causes, such as Sjögren’s syndrome or radiation therapy, also promotes stagnation and stone formation. Inflammation or trauma to the salivary duct can provide an organic nidus for mineral deposition, initiating calcification. Less commonly, systemic conditions like Gout may lead to salivary stones composed of uric acid crystals rather than calcium salts.
Recognizing the Signs and Symptoms
The most noticeable signs of a salivary gland stone occur when the stone partially or completely obstructs the duct. The characteristic symptom is pain and swelling of the affected gland that worsens during or immediately after eating. This happens because food stimulation causes the gland to produce saliva, which then backs up behind the blockage, causing pressure and discomfort.
This pain is often described as a sudden, sharp ache that can last for one to two hours before subsiding as saliva flow lessens. The symptoms are frequently intermittent; they may come and go as the stone shifts position or as saliva flow temporarily overcomes the partial obstruction. Swelling and pain are most often felt under the jaw or, less commonly, near the ear, depending on the affected gland.
If the blockage persists, the stagnant saliva can lead to a bacterial infection of the gland, known as sialadenitis. Signs that an infection has developed include fever, persistent swelling, redness over the gland, and possibly a foul taste in the mouth due to pus drainage. Any development of these more severe symptoms requires prompt medical attention.
Prevention and Management Strategies
Simple lifestyle adjustments can help prevent stone formation by ensuring consistent saliva flow and reducing concentration. Staying well-hydrated is a primary preventative measure, as drinking plenty of water keeps the saliva thin and less concentrated. Consistent hydration reduces the likelihood of supersaturation.
Stimulating saliva production can help flush out small stones or prevent stagnation. Sucking on sialogogues, such as sugar-free sour candies or lemon slices, increases saliva flow, which can sometimes naturally expel a stone. Applying gentle massage to the affected gland, sweeping the fingers forward toward the duct opening, can also encourage the stone to move.
Applying moist heat, such as a warm compress, to the swollen gland can help alleviate discomfort and relax the surrounding tissues. Over-the-counter pain relievers can manage tenderness and inflammation. However, if pain is severe, swelling is persistent, or a fever develops, these are signs of a potential infection or complete blockage, and a medical professional should be consulted immediately for evaluation and possible stone removal.