Sonography of the salivary glands

Due to their superficial position, the parotid, the submandibular, and the sublingual glands can be imaged with high-resolution transducers. In acute inflammatory diseases sonography can differentiate between obstructive or non-obstructive sialoadenitis. Abscess formations may be detected and the maturation of the colliquation may be controlled. Abscesses may be punctured under US guidance. In Sj?gren's syndrome the sonographic changes correlate with the histological destruction, and in acute forms hypervascularization is found in color Doppler. In fibrotic cases the stimulation-induced hyperemia is impaired. In sialoadenosis inflammatory and tumorous lesions can be ruled out by sonography. Tumors of the salivary glands can be visualized with high sensitivity. Like other imaging methods the specificity in assessment of the histology of a tumor is low. Multilocular lesions, such as sarcoidosis, lymphoma, metastases, or cystadenolymphoma, are discussed. In deep located, malignant tumors or when the tumor cannot be delineated completely, MR or CT are obligatory to delineate the tumor. Sonography enables the diagnosis of cysts or ranulae. The accuracy of sonography in assessment of sialolithiasis is approximately 90%. Non-opaque stones can be visualized, too; however, small stones of less than 2 mm are difficult to detect since the posterior shadow may be missing. The concrements can be differentiated into intraductal or intraglandular stones. Indirect signs, such as ductal dilatations or inflammatory changes, may be found. Pseudotumorous lesions, such as hypertrophy of the masseter muscle, tuberculosis, sarcoidosis, or lymphoepithelial lesions in AIDS, are discussed. In children the main differential diagnosis of salivary gland pathologies are addressed. In many diseases sonography is the first-line imaging modality in assessment of salivary glands.     

Sonography of the thyroid and parathyroid glands

Sonography is the first line modality for assessment of thyroid and parathyroid pathologies. Sonographic and color Doppler patterns of diffuse and focal pathologies of the thyroid are presented in this article. The accuracy of sonography in the localization of enlarged parathyroid glands is also discussed. The limitations of sonography in specifying focal thyroid diseases and the problems in localizing ectopic parathyroid adenoma are addressed.     

Sonography of the adrenal glands: normal glands and small masses

To evaluate sonographic imaging of the normal adrenal glands, anterior transverse and longitudinal scans were made on 200 patients who had no evidence of adrenal disease. In 78 additional patients who were suspected of having adrenal masses, anterior and posterior transverse and longitudinal scanning and longitudinal oblique scanning were done. Anterior transverse scanning proved to be the best single method of scanning the adrenal gland and small adrenal masses. The normal adrenal gland which is 3-6 mm thick and adrenal masses as small as 1.3 cm can be delineated. Although the frequency of visualizing normal adrenal glands (78.5% on the right and 44% on the left) with sonography is not as high as with CT, masses are more readily detected than the normal glands. The accuracy for detecting adrenal masses is very high, with a false-negative rate of only 3%. Sonography can be a useful screening test for many patients who are suspected of having adrenal masses. However, for obese patients the image is degraded and a higher false-positive rate (3.5%) is obtained. CT provides better resolution for such patients.     

Ultrasonography of the salivary glands

Sonography and computed tomography play complementary roles in imaging mass lesions in the salivary glands and their surroundings. Ninety per cent of parotid tumors originate from the superficial lobe, and we consider sonography to be the method of choice for imaging these lesions. The sensitivity of high-resolution sonography in detecting intraparotid tumors approaches 100 per cent, and ultrasound is therefore an excellent method to evaluate patients with parotid swelling. It may provide clinically useful information by precisely outlining the tumor borders or by detecting multiple or bilateral lesions. We restrict our use of CT to tumors that appear to extend beyond the borders of the parotid gland with possible invasion of surrounding soft tissues or bone. CT is also the method of choice for differentiating lesions of the deep lobe from parapharyngeal tumors and for staging carcinomas. Although ultrasound supplemented with computed tomography should replace conventional sialography in the work-up of parotid neoplasms, sialography remains the method of choice for evaluating patients with chronic sialadenitis, autoimmune diseases, and sialolithiasis. The role of sonography in these conditions is limited to ruling out a parotid neoplasm, assessing the extent of abscess formation, or assisting in localizing calculi in selected patients.     

MR of the salivary glands

MR has become the examination of choice for imaging salivary gland neoplasms. The improved soft tissue contrast of MR represents a significant improvement over CT, particularly for extension outside the gland. The appearance of various tumors and inflammatory processes is described.     

Endoscopy of the salivary glands

The author has developed an original method of exploration of the salivary glands: ultrafine fibroscopy. After briefly describing the equipment, the method and the indications, he demonstrates how it is now possible to extract stones via the natural passages using a miniaturized basket catheter, avoiding the need for more extensive surgery.     

Assessment of post-radiotherapy salivary glands

Salivary glands are usually irradiated during radiotherapy for head and neck cancers, which can lead to radiation-induced damage. Radiation-induced xerostomia (oral dryness) is the most common post-radiotherapy complication for head and neck cancer patients and can reduce the patient's quality of life. Accurate and efficient salivary gland assessment methods provide a better understanding of the cause and degree of xerostomia, and may help in patient management. At present, there are different methods for the assessment of salivary gland hypofunction; however, none of them are considered to be standard procedure. This article reviews the value of common methods in the assessment of post-radiotherapy salivary glands.     

Study of the salivary glands in 1990

Radiologic examination of the salivary glands can provide clinically useful information that may help to establish the diagnosis and indicate appropriate therapy. US and conventional sialography remain the standard methods of examination for inflammatory diseases and superficial parotid masses. However, CT and MR have allowed a new means of examination of parotid lesions, or of lesions around the parotid gland. MR appears to be the procedure of choice to investigate adenoid cystic carcinoma, recurrence and tumors expanding into the pterygopharyngal space or the sub-tonsillar space. Stenon duct endoscopy is a new imaging and therapeutic procedure to be introduced into the therapeutic strategy in these patients.     

Computed tomography of the submandibular salivary glands

Computed tomography offers a convenient method for the evaluation of the submandibular salivary glands and their surroundings. Normal measurements were established based on 38 normal subjects. The visualization of the ductal system in the gland and the relationship of the gland to the platysma muscle were recorded. The CT scans of 12 patients with a tongue base carcinoma and 4 patients with a verified obstruction of the submandibular duct were also reviewed to establish how the glands are affected by extrinsic lesions. The normal glands measured 28 x 18 mm (+/- 5 mm) in the axial plane. Two patients with unilateral hypoplasia of the gland were found in the normal group. Visualization of the intraglandular duct is not a specific finding since it was observed in more than 25 per cent of the normal group. Displacement and bulging of the platysma muscle by the submandibular gland can be a sign of glandular enlargement. It was also seen in 9 out of 12 patients with carcinoma of the base of the tongue.     

Comparison of methods of imaging the salivary glands

Surgery on the salivary glands can be a considerable surgical challenge because of their complex and delicate structure. To avoid damage to the facial nerve, and because pleomorphic adenomas are the most common space-occupying lesions of the parotid glands, a formal parotidectomy is often undertaken. To plan the surgical approach better and to avoid unnecessary surgery in some patients, the search for the ultimate imaging technique for the salivary glands continues. A few recent reports comparing various imaging techniques for the salivary glands are discussed in this review.     

Calcifications simulating sialolithiasis of the major salivary glands

Calcifications found in routine and normal radiographs of the oral and facial region may turn out to be an interesting diagnosis. Although most of the radiopacities may be sialoliths, other differential diagnoses must not be exempted, such as calcified lymph nodes, phleboliths and other vascular calcifications, tuberculosis of lymph nodes or of the salivary gland itself. Several cases are presented which simulated pathological calcifications of the orofacial region and were diagnosed primarily as sialoliths, but further examinations revealed other pathology. These cases together with several suggested diagnostic modalities are discussed in this paper.     

Diffusion-weighted echoplanar MR imaging of the salivary glands

OBJECTIVE: We determined the apparent diffusion coefficients of normal and dysfunctional salivary glands. SUBJECTS AND METHODS: A diffusion-weighted single-shot spin-echo type of echoplanar MR imaging was performed on the parotid or submandibular glands, or both, in 36 healthy subjects, 20 patients with Sj?gren's syndrome, and six patients with sialoadenitis. The apparent diffusion coefficient of the salivary gland was calculated using two b factors (b = 500 and 1,000 sec/mm(2)). RESULTS: The apparent diffusion coefficient was lower in the parotid glands (0.28 x 10(-3) mm(2)/sec) than that of the submandibular glands (0.37 x 10(-3) mm(2)/sec). The apparent diffusion coefficient was increased in sialoadenitis, whereas it decreased with abscess formation. The apparent diffusion coefficients of the parotid glands in patients with Sj?gren's syndrome correlated with the salivary flow rates but not with the sialographic gradings of the glands. We also found a correlation of the decreases in apparent diffusion coefficients with the severity of gland damage as assessed on T1-weighted MR images. CONCLUSION: Diffusion-weighted echoplanar MR imaging may reveal diseased states of the salivary glands.