The parotid glands are small exocrine glands located superficial and around the ramus of the jaw, which are rarely affected by diseases of any kind. Occasionally, however, the radiologist is asked to examine them (usually in the setting of pain or swelling).

In children, the main cause for painful enlargement of the parotid is an entity called viral parotitis, usually caused by Mumps. This paramyxoviral disease is spread by droplets or direct contact, and its prevalence has drastically decreased since vaccination started in the 1970's, being more common in underdeveloped countries. The children may present with viral symptoms like fever, dry cough, and body pain, but a dominant feature may be the viral parotitis, which appears on US as heterogenicity of the parenchyma with hyperemia.

Differential diagnosis of an enlarged parotid gland includes acute bacterial parotitis, HIV parotitis, parotitis related to tuberculosis, Mickulicz disease, Sjögren disease, sialolithiasis, chronic recurrent parotitis, sarcoidosis, and benign and malignant tumors.