The occurrence of stones within the salivary glands (sialolithiasis) involves the submandibular and parotid glands with the majority (up to 90%) in the submandibular gland. Usually stones are radiopaque, composed of calcium phosphate, are solitary and can be asymptomatic. Up to 22% will have multiple calculi. Bilateral stones may occur but are rare (2%). The propensity for occurrence in the submandibular gland is thought to be due to the nature of its secretions, which are thicker, and more mucous. Additionally, greater alkalinity and concentration of hydroxyapatite and phosphatase are contributing factors. The anatomy of Wharton's duct contributes to stone formation, as it assumes an uphill course and its orifice is smaller than the overall ductal caliber. 85% of stones occur within Wharton's duct with 30% located near the ostium. Despite the prescence of stones, the flow of saliva can continue unabated due to the duct's generous caliber and the potential for pseudodiverticula to form. Obstructing stones may result in gland atrophy and/or abscess and predispose to stricture formation. The only systemic disease known to cause sialolithiasis is gout, with uric acid stones being generated. Sjogren's is more commonly associated with sialadenitis. Non contrast CT is the test of choice for radiologic evaluation although up 80% of stones can be seen on plain films. Stones may be massaged out of Wharton's duct. If this is unsuccessful, transoral ductotomy or gland and duct excision may be necessary. Extracorporeal shock wave lithotripsy has been used with mixed success.
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