[Ultrasound diagnostics in Sjögren's syndrome]

Ultrasound of the salivary glands is a specific examination for detecting pathology of salivary glands in the diagnosis of Sjögren's syndrome. It is easy to learn, rapidly performed, non-invasive and inexpensive. Other imaging techniques, such as sialography and scintigraphy, are currently only rarely performed. For the examination, linear ultrasound probes with frequencies between 7 and 12 MHz are recommended. Such probes are already widely available to the rheumatologist performing musculoskeletal ultrasound. The parotid and submandibular glands are bilaterally scanned both in longitudinal and transverse planes as a standard.Normal salivary glands have uniformly hyperechoic and homogeneous tissue. They can be clearly delineated from the surrounding muscles and soft tissue and appear similar to the thyroid gland. The salivary glands are typically hypoechoic and inhomogeneous in Sjögren's syndrome. Focal or diffuse hypoechoic or anechoic foci are found in the glands. The submandibular glands may become atrophic (sagittal diameter <8 mm). Particularly in disease flares, the parotid glands may become enlarged (sagittal diameter >20 mm). The sensitivity for the diagnosis is 60 to 90% and the specificity is over 90%.Doppler sonography does not further improve the diagnostic accuracy. Sonography has thus become an important tool in the diagnosis of Sjögren's syndrome.