How reliable is sonography in the assessment of sialolithiasis?

OBJECTIVE

The purpose of this study was to determine the value of sonography for the diagnosis of salivary gland calculi.

SUBJECTS AND

METHODS

In this study, 82 salivary glands in 79 consecutively registered patients with acute or recurrent parotid or submandibular gland swelling were examined with 7.5-12 MHz linear probes. All sonographic examinations were performed by two experienced radiologists without knowledge of the final diagnosis. The reference standard was digital sialography and sialendoscopy with or without surgery for 54 salivary glands and digital sialography alone for 28 glands.

RESULTS

Sialolithiasis was present in 44 glands and was absent in 38 glands as confirmed by the final diagnosis. The overall sensitivity, specificity, accuracy, and positive and negative predictive values of sonography in the detection of calculi were 77%, 95%, 85%, 94%, and 78%, respectively. False-negative sonographic findings were associated with calculi with a diameter less than 3 mm in nondilated or dilated salivary ducts; most calculi with a diameter of 3 mm or greater were correctly identified. False-positive findings were caused by ductal stenosis with wall fibrosis, which was erroneously interpreted as lithiasis.

CONCLUSION

Because of its limited sensitivity and limited negative predictive value, sonography does not allow reliable exclusion of small salivary gland calculi. Therefore, further diagnostic investigations are recommended to detect calculi in patients with normal sonographic findings and suspected lithiasis.