The most common developmental salivary gland disorder is salivary tissue in an ectopic location such as the nasopharynx or middle ear (salivary gland choristoma). Other potential developmental disorders include aplasia/agenesis, duplication, and cysts. Salivary gland ducts can be atretic, imperforate, ectatic, or duplicated.

Salivary gland agenesis is a rare anomaly. Lack of salivary gland development can be complete, or (more commonly) involve a single gland. There are various potential associated anomalies, such as absence of the lacrimal puncta. This disorder usually occurs with an autosomal dominant pattern of inheritance. Affected children suffer severe dryness of the mouth and are prone to secondary dental abnormalities.¹

Mandibulofacial dysostosis syndrome includes agenesis or hypoplasia of the parotid glands in conjunction with masseter muscle agenesis/hypoplasia, cleft palate, and microstomia. Other facial bone deformities also occur in these children. Mandibulofacial dysostosis syndrome has an autosomal dominant pattern of inheritance. The anomalies in this syndrome predominantly involve derivatives of the first and second branchial arches.

Parotid aplasia and ectopic salivary gland tissue can occur in the various oculo-auriculo-vertebral syndromes such as Goldenhar syndrome and hemifacial microsomia (see Figure 26-21 in Chapter 26).²

Lacrimo-auriculo-dento-digital syndrome is a rare autosomal dominant ectodermal dysplasia that includes aplastic/hypoplastic salivary and lacrimal glands/ducts, cup-shaped ears, defective hearing, hypodontia and enamel hypoplasia, and distal limb anomalies.

Viral

Acute viral infections of the salivary glands result in painful selling that is often bilateral. Acute viral sialadenitis due to mumps is the most common cause of salivary gland enlargement in children. Other viral pathogens include cytomegalovirus, influenza virus, and coxsackievirus. Diagnostic imaging evaluations are usually not required for these children unless there is an unusual clinical presentation or evidence of a complication. Cross-sectional imaging shows nonspecific salivary gland enlargement. On sonography, the edematous gland is hypoechoic. Color Doppler images frequently show prominent vascularity in the gland. There is usually an abnormal hyperintense character in T2-weighted MR sequences.³

Salivary gland enlargement is common in children with HIV infection. The gland enlargement is usually due to infiltration with CD8-positive lymphocytes. Lymphoepithelial cysts are less common than in adults.

Bacterial

Most suppurative infections of the salivary glands are due to Staphylococcus aureus, Streptococcus viridans, Streptococcus pneumoniae, or anaerobic bacteria. Children with these infections experience a rapid onset of symptoms that include pain, swelling, and redness. Either the parotid or submandibular glands may be affected; lingual gland involvement is rare. Acute bacterial sialadenitis occurs with an increased frequency in premature newborns, as well as chronically ill and dehydrated older children. Sonography and CT are sometimes useful for these children to confirm inflammation of the gland and to identify an abscess. The risk of an abscess is increased in patients with excretory duct obstruction (e.g., stone or fibrosis).⁴

The CT findings of acute bacterial sialadenitis are somewhat variable. A heterogeneous appearance of an enlarged gland is typical. On unenhanced images, edema and cellular infiltration result in increased attenuation (Figure 31-1). Unenhanced images are particularly helpful for the detection of calculi. Inflammatory hyperemia causes prominent contrast enhancement. Focal areas of inflammation or microabscesses may result in a heterogeneous pattern of enhancement (Figure 31-2). A larger abscess appears as a low-attenuation focus surrounded by a rim of prominently enhancing inflamed tissue. Adjacent soft tissue planes are often ill-defined, and regional lymphadenopathy is common.

Sonography of uncomplicated bacterial salivary gland infection demonstrates gland enlargement, hypoechogenicity, and parenchymal heterogeneity. There is hyperperfusion on Doppler evaluation. Enlargement of adjacent lymph nodes is common. An abscess appears as a hypoechoic or anechoic focus with posterior acoustic enhancement and irregular margins. There is often echogenic debris in the cavity. A mature abscess is surrounded by a hyperechoic and hypervascular rim.⁵

Salivary gland infection can occur in children with cat scratch disease. Cat scratch disease is a worldwide, nonepidemic infection caused by the Gram-negative bacillus Bartonella henselae. With salivary gland involvement, sonography demonstrates enlargement, often with hypoechoic areas within the gland. Concomitant cervical lymphadenitis is common.⁶

Recurrent Parotitis of Childhood

Recurrent parotitis of childhood (juvenile recurrent parotitis; recurrent acute parotitis) is an inflammatory condition of the parotid glands that can occur with or without an associated infection. Streptococcus viridans is an occasional cause. The clinical features include intermittent episodes of pain, fever, and parotid gland swelling. Frequently, there is no evidence of an underlying illness. The findings are usually unilateral; when bilateral, the symptoms tend to more pronounced on one side. The episodes tend to initiate between the ages of 2 and 5 years, and persist until the teens. The intervals between episodes vary from weeks to months to years. Recurrent parotitis occurs more frequently in males, and is sometimes associated with a history of prior mumps parotitis.^7,8

Sialography of patients with recurrent parotitis is sometimes normal, or shows sialectasis. Punctate pools of contrast may accumulate within the gland (Figure 31-3). The main duct empties appropriately and there is no evidence of a stricture. Sonography shows parotid gland enlargement, usually bilateral. Multiple hypoechoic foci, approximately 2 to 4 mm in diameter, are present in the parenchyma; these represent the manifestations of peripheral sialectasis and adjacent lymphocytic infiltration (Figure 31-4). CT and MR show an enlarged, somewhat heterogenous gland, without ductal dilation (Figure 31-5). There is prominent contrast enhancement during episodes of acute inflammation.^9,10

Autoimmune Disease

Salivary gland inflammation (sialadenitis), most often involving the parotid glands, can occur in association with autoimmune diseases such as systemic lupus erythematosus. The findings are usually bilateral. Patients may complain of a dry mouth and dry eyes. Early in the course, parotid gland sonography is usually normal. Eventually, the glands become enlarged and there may be diffuse hypoechoic areas, multiple cysts, or abnormal lobulation of the gland margins. Inflammation results in salivary gland enlargement on CT and homogeneous increase in the attenuation values. Scattered foci of diminished enhancement are sometimes present on images obtained following contrast administration.

Salivary gland involvement can occur with Sjögren syndrome. In children, this condition is more common in boys than in girls. Approximately 30% of patients with Sjögren syndrome have clinical manifestations of salivary gland involvement. The major pathological features in the salivary glands are lymphocytic and plasma cell infiltration and gland destruction. Sialography demonstrates duct destruction and irregularity. Classically, the imaging pattern includes pruned truncated ducts and punctate or small globular contrast collections peripherally. There is relative sparing of the central ductal system. Extravasation of contrast material occasionally occurs. The salivary glands may be enlarged and have a multinodular appearance on cross-sectional imaging studies. The typical sonographic features are parenchymal hyperperfusion and the presence of multiple small, oval, hypoechoic foci.⁵

The term sialectasis refers to dilation of the salivary ducts. Punctate sialectasis indicates saccular dilation of small ducts within the gland. Sialodochiectasis refers to dilation of the large ducts. The most common causes of punctate sialectasis in children are inflammatory conditions, including autoimmune diseases. Sialectasis can also occur as a complication of congenital ductal abnormalities or ductal obstruction by a stone, stricture, or mucous plug. The predominant clinical manifestations are those of pain and gland swelling, often with an intermittent pattern. Overt signs of infection are lacking.¹¹

Imaging studies demonstrate a heterogeneous character of the involved salivary gland. Sialography is the most accurate technique for demonstrating the small peripheral periductal fluid-filled cavities. In the absence of obstruction, the major duct is often normal. Peripheral ductal irregularity and pruning are common (Figure 31-6). The detection of an underlying stricture, stone, or mass is an important function for imaging studies in patients with sialectasis. Noninvasive depiction of the major ducts is possible with MRI. CT is particularly useful for detection of an obstructing stone. With sonography, sialectasis results in a diffusely heterogeneous echotexture of the gland. A calculus appears as a hyperechoic focus with acoustic shadowing, often within a dilated duct.

Sialolithiasis is uncommon in children. The submandibular glands are the most common sites. Patients with cystic fibrosis are prone to sialolithiasis. Ductal obstruction by a sialolith or a stricture related to a passed stone can cause recurrent swelling (often exacerbated by eating) or bacterial infection. Standard radiographs allow visualization of many radiopaque salivary stones, but superimposition of osseous structures can interfere with visualization of some stones by this technique (Figure 31-7). CT is sensitive for the detection of calcified stones (Figure 31-8). With sonography, a stone appears as an echogenic focus that has acoustic shadowing. MR shows a sialolith as a hypointense focus within the lumen of a dilated duct. MR may also demonstrate manifestations of sialadenitis caused by the obstructing stone. With acute inflammation, the gland is enlarged and has low signal intensity on T1-weighted images and high signal on fat-suppressed T2-weighted images. With long-standing involvement, gland atrophy can occur.^12,13