Head and Neck ImagingSialolithiasis
salivary calculus (stone). Sialolithiasis is probably the most frequent salivary gland pathology beyond the second decade of life. It is most commonly seen in the
submandibular gland and duct (about 80% of cases), followed by the
parotid gland and duct; sialolithiasis is rare in the
sublingual gland. Most stones are solitary, but multiple stones may be present. Sialolithiasis is the most frequent cause of recurrent
sialadenitis. The higher frequency in the submandibular gland is related to the pH of saliva (alkaline in the submandibular gland, acidic in the parotid gland), to the viscosity of saliva (more mucous in the submandibular gland) and to anatomical factors (uphill course of
Whartons duct).
Submandibular sialolithiasis is most often situated near the orifice of Wharton's duct or at the bend of the duct passing behind the mylohyoid muscle. Parotid stones are usually seen in the distal part of Stensens duct. The typical symptoms of sialolithiasis are pain and swelling with eating; this may occur at every meal, or only once in a while. Superinfection causes fever and cellulitis. Sometimes a painless mass, simulating tumour may be present. Sialolithiasis may be asymptomatic and discovered by chance.
The radiological evaluation includes plain radiography, ultrasound, conventional sialography and CT. Large, well-calcified stones can usually be recognized on a plain radiographic study. Smaller or faintly calcified stones are more likely to be detected using CT (Fig.1). Ultrasound is an appropriate noninvasive technique for detecting sialoliathiasis, including non-calcified concretions. Sialography gives a detailed visualisation of the ductal morphology, permitting the diagnosis of opaque and nonopaque stones (Fig.2) and also allowing identification of ductal strictures. Recently, the potential value of MR-sialography has been demonstrated.
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Plain (a) and contrast-enhanced (b) axial CT image of parotid glands. A small calcified stone (arrowhead) is seen at the orifice of the left Stensen's duct. Diffuse enhancement of the left parotid gland: sialadenitis.
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Sialolithiasis, Fig.1 (a) | | Sialolithiasis, Fig.1 (b) | | Sialolithiasis, Fig.2 |