Sialoliths, or salivary stones, are the most common disease of the salivary glands in middle-aged patients. More than 80 percent of salivary sialoliths occur in the submandibular duct or gland, six percent to 15 percent occur in the parotid gland, and about two percent are in the sublingual and minor salivary glands. (J Craniofacial Surg 2006;17:549.)
The exact etiology of sialolith formation remains unknown, but it is thought that the more alkaline, viscous, mucus-rich saliva, which contains a higher percentage of calcium phosphates, in addition to the long and sinuous position of Wharton's duct, contributes to stasis, making the submandibular salivary system more prone to the development of sialoliths than the parotid gland. (Otolaryngol Clin NA 1999;32:795 and J Contemp Dent Pract 2005;3:127.)
It is known that systemic diseases (gout, Sjögrens), medications (anticholinergics, antisialogogues), local trauma, head and neck radiotherapy (Oral Dis 2002;8:77), being elderly (J Contemp Dent Prac 2005;6:127), and renal impairment (J Am Dent Assoc 1986;113:612) also can predispose patients to sialolith formation. It is estimated that sialolithiasis affects 12 of every 1000 patients in the adult population (Lancet 1992;339:1333), with men affected twice as often as women. (Schow SR, et al. Diagnosis and management of salivary gland disorders. In: Peterson LJ, et al, eds. Contemporary Oral and Maxillofacial Surgery. New York: Mosby, 1988:495.)
Most salivary calculi are small, usually less than 1 cm, but megaliths or giant calculi have been reported. (J Craniofacial Surg 2006;17:549.) They are composed of mineralized debris that accumulates within the duct lumen including calcium phosphate, carbon, and trace amounts of magnesium, potassium, and ammonium. (Micron and Microscopica Acta 1983;14:219.) Salivary calculi grow by deposition at an estimated rate of 1 mm to 1.5 mm per year. (Br J Oral Maxillofac Surg 2003;41:414.) In the submandibular duct, multiple salivary stones are rare. (J Laryngol Otol 1985;99:1313.)
Sialoliths are most the common cause of acute and chronic infections of salivary glands. The resulting salivary stasis from stone formation allows bacterial ascent into the gland and then increases the risk of bacterial colonization and acute salivary gland infection. (Otolaryngol Clin NA 1999;32:795.) Because stones are more common in Wharton's duct, so are acute bacterial infections of the submandibular gland versus the parotid. (Rev Infect Dis 1990;12:591.)
Some sialoliths may be asymptomatic and identified incidentally during jaw imaging. Approximately 30 percent of the time, submandibular sialolithiasis presents with painless swelling, but the classic symptoms are secondary to duct obstruction and include pain and swelling of the involved gland during eating when saliva production is at its maximum and salivary flow is forced against a fixed obstruction. Subsequent gradual reduction of the swelling can occur, but as salivary flow is stimulated, painful symptoms can recur. (Lancet 1992;339:1333.) Patients may have waxing and waning symptoms of episodic swelling and discomfort, or may have more persistent symptoms as salivary fluid accumulates within the duct.
Occasionally stones can be palpated with digital examination; they feel like hard small pebbles. Less commonly, they are seen as granular masses at the gland duct entrance. To identify the degree of obstruction, the emergency physician can try to squeeze saliva from the gland to see if it is blocked. Severe obstruction of the gland is shown by exquisite tenderness, intraoral and/or extraoral swelling, and the absence of saliva on palpation. (Dent Clin NA 2005;49:241.)
The differential diagnosis of salivary calculi includes infections (bacterial and viral), inflammatory conditions (Sjögren's, sarcoidosis, radiotherapy reaction), and masses (neoplastic and nonneoplastic).
Diagnostic imaging to identify presumed salivary calculi include conventional radiography, sialography, and ultrasonography. But currently, high-resolution noncontrast computerized tomography scanning is the imaging modality of choice for the evaluation of salivary stones. This is because many calcified sialoliths are not detected by conventional radiography until they are 60 percent to 70 percent calcified (Otolaryngol Clin NA 1999;32:793), with at least 20 percent of submandibular and 50 percent of parotid stones not identifiable on intraoral and panoramic radiography.
In sialography, dye is injected into the duct, and it can demonstrate obstruction as a filling defect in the duct and duct stenosis. It cannot, however, demonstrate small secretion plugs or secretion plaques, and it is contraindicated in acute infection or in patients with a significant contrast allergy. Ultrasonography identifies calculus as white echogenic structures with glandular inflammatory changes of the salivary gland, but it is unable to diagnose any other etiology of gland swelling.
Small caliber endoscopy was developed to treat obstructive disorders of the salivary gland duct system. (Oral Surg, Oral Med, Oral Pathol, Oral Radiol, Endodon 1997;84:578.) It is both diagnostic and therapeutic, and has the benefit of differentiating between obstructive inflammatory conditions and calculi. Despite most sialoliths being composed of calcium elements, they are not associated with systemic calcium abnormalities, so a serum calcium level is not needed.
Sialoendoscopy, fluoroscopy-guided wire basket extraction, lithotripsy, and surgical removal are other options when expectant management fails or is inappropriate. The decision about which technique to utilize depends on stone size, location, and procedure availability. The stone will stay in the gland until it is removed. Typically stones less than 2 mm in diameter can be treated without surgical intervention. A conservative approach, including oral analgesia, hydration, local warm heat therapy, massage to “milk” out the stone, sialogogues (i.e., tart hard candies) to promote ductal secretions, and discontinuation of anticholenergic medications when possible are recommended. In most cases, removing the stone will relieve pain except when an associated infection exists. Antibiotics covering oral flora for gland superinfection are recommended. Severe obstruction usually requires surgical intervention, especially when the obstruction is close to the gland. (Dent Clin NA 2005;49:241.)
This patient was found to have a 6 mm right submandibular stone that was surgically removed at the bedside by an otolaryngologist using local anesthesia. He tolerated the procedure well, and was discharged home.