Submandibular Sialolith

A 34-year-old man presented with a 2-year history of intermittent painful swelling below the angle of the right mandible. There had never been an indication of infection, and the symptoms worsened after eating.

Physical examination revealed a large, firm, nonmobile, minimally tender mass beneath the right side of the mandible. A lateral skull radiograph (Figure 1) was obtained before a computed tomography (CT) of the area.

Based on the symptoms and the results of imaging studies, the man received a diagnosis of sialolith, specifically a submandibular sialolith.

Discussion. Submandibular sialoliths are more common than parotid sialoliths and tend to be radiopaque more often than parotid sialoliths.¹ A sialolith is formed around a nidus of retained material such as thickened mucus, or debris such as calcium phosphate and hydroxyapatite. Most submandibular stones are composed of calcium phosphate and hydroxyapatite. Patients with a history of gout, diabetes mellitus, hypertension, cystic fibrosis, xerostomia, or dehydration also have a propensity to form stones.^1,2

Anatomically, the Wharton duct is long and narrow (5 cm long and 1.5 mm in diameter) and thus is a difficult passageway for a stone of any size to traverse. Sialoliths may occur at any age, and there is a predilection in men.²

Symptoms wax and wane as the stones enlarge and further compress the duct. With a partial obstruction, pain and swelling in the area occur after meals and tend to resolve quickly; a full obstruction leads to chronic enlargement of the gland and possibly acute suppurative sialadenitis or stricture.² If submandibular stones are large enough, they may be palpable in the anterior two-thirds of the duct.^1-3

Skull or dental radiographs often reveal the presence of a submandibular sialolith, but up to 20% of such stones are radiolucent. Up to 60% of parotid sialoliths are radiolucent.¹ Thin-slice CT scanning of the area often reveal sialoliths, is up to 10 times more accurate than plain radiographs, and offers excellent detail as to the exact location of the stone. Thus CT scans are the preferred imaging method.³ Figures 2 and 3 are CT scans of a different patient, demonstrating several small submandibular stones.

Conservative treatment of sialolith consists of hydration, application of moist heat, massaging or milking the gland, the use of sialogogues to promote ductal secretions, discontinuation of anticholinergic medications, pain relief via nonsteroidal anti-inflammatory drugs and, if sialadenitis is present, antistaphylococcal antibiotics.³

It is possible to remove small stones via massaging the gland, or using serially graded lacrimal probes for stones under 2 mm in diameter; in the case of very large sialoliths as seen in our patient, surgical intervention is required to remove the stone. Surgical intervention includes such techniques as laser lithotripsy with or without sialoendoscopy, sialoendoscopy alone, direct removal via the transoral approach, or, in cases of stones that are unable to be removed via these methods, transcervical excision. Transcervical excision does present the risk of damage to the lingual and hypoglossal nerves.^2,3 Recurrence of submandibular stones is about 20%.²

Differential diagnosis. A ranula is a retention cyst that occurs on the floor of the mouth and is a cystic dilation of either a sublingual gland or the submandibular duct. Patients experience fullness and pain in the location of the ranula, and physical examination reveals a smooth, soft swelling at the anterior floor of the mouth. Ranulas tend to gradually enlarge, and may spontaneously rupture and then reoccur: the size of the cyst may vary. These lesions are radiolucent on plain radiographs but are seen on CT scans. Treatment is surgical marsupialization.¹

Submandibular tumors should be considered when a patient has enlargement of the gland without periods of decreased swelling, nonresponsiveness to conservative treatment, and facial nerve dysfunction, and when physical examination shows a firm, fixed mass. CT scans of the area will help delineate a tumor from a sialolith, and a fine-needle biopsy will allow the otolaryngologist-surgeon to determine the best treatment method.³ 

References:

1. Woodson GE. Salivary gland disorders. In: Woodson GE, ed. Ear, Nose and Throat Disorders in Primary Care. Philadelphia, PA: WB Saunders; 2001:141-156.
2. Butt FY-S. Benign diseases of the salivary glands. In: Lalwani A, ed. Current Diagnosis and Treatment in Otolaryngology—Head and Neck Surgery. 3rd ed. New York, NY: McGraw Hill/Lange; 2012:317-332.
3. Fazio SB, Emerick K. Salivary gland stones. UpToDate. http://www.uptodate.com/contents/salivary-gland-stones. Accessed April 18, 2016.