Stones composed of calcium salts often obstruct salivary glands, causing pain, swelling, and sometimes infection. Diagnosis is made clinically or with CT, ultrasonography, or sialography. Treatment involves stone expression with saliva stimulants, manual manipulation, a probe, or surgery.
The major salivary glands are the paired parotid, submandibular, and sublingual glands. Stones in the salivary glands are most common among adults. Eighty percent of stones originate in the submandibular glands and obstruct the Wharton duct. Most of the rest originate in the parotid glands and block the Stensen duct. Only about 1% originate in the sublingual glands. Multiple stones occur in about 25% of patients.
Most salivary stones are composed of calcium phosphate with small amounts of magnesium and carbonate. Patients with gout may have uric acid stones. Stone formation requires a nidus on which salts can precipitate during salivary stasis. Stasis occurs in patients who are debilitated, dehydrated, have reduced food intake, or take anticholinergics. Persisting or recurrent stones predispose to infection of the involved gland (sialadenitis).
Obstructing stones cause glandular swelling and pain, particularly after eating, which stimulates saliva flow. Symptoms may subside after a few hours. Relief may coincide with a gush of saliva. Some stones cause intermittent or no symptoms.
If a stone is lodged distally, it may be visible or palpable at the duct’s outlet.
If a stone is not apparent on examination, the patient can be given a sialagogue (eg, lemon juice, hard candy, or some other substance that triggers saliva flow). Reproduction of symptoms is almost always diagnostic of a stone.
CT, ultrasonography, and sialography are highly sensitive and are used if clinical diagnosis is equivocal. Contrast sialography may be done through a catheter inserted into the duct and can differentiate between stone, stenosis, and tumor. This technique is occasionally therapeutic. Because 90% of submandibular calculi are radiopaque and 90% of parotid calculi are radiolucent, plain x-rays are not always accurate. Ultrasonography is being used increasingly and has reported sensitivities for all (radiopaque and radiolucent) stones of about 60 to 95% and specificities between 85 and 100%. The role of MRI is evolving; reported sensitivities and specificities are > 90% and it appears to image small stones and distal ducts more sensitively than ultrasonography or contrast sialography.
Analgesics, hydration, and massage can relieve symptoms.
Antistaphylococcal antibiotics can be used to prevent acute sialadenitis if started early.
Stones may pass spontaneously or when salivary flow is stimulated by sialagogues; patients are encouraged to suck a lemon wedge or sour candy every 2 to 3 h. Stones right at the duct orifice can sometimes be expressed manually by squeezing with the fingertips. Dilation of the duct with a small probe may facilitate expulsion.
Surgical removal of stones succeeds if other methods fail. Stones at or near the orifice of the duct may be removed transorally, whereas those in the hilum of the gland often require complete excision of the salivary gland. Stones up to 5 mm in size may be removed endoscopically.