“Sial” refers to saliva, “aden” refers to a gland, and “itis” is inflammation, so acute sialadenitis is the sudden inflammation of any of the salivary glands, the major ones being the parotid, submandibular and sublingual gland.
Sialadenitis usually affects a single parotid gland rather than both, and is most common among individuals in their 50s and 60s but can happen at any age, even in a newborn.
Acute sialadenitis is most often caused by the bacteria Staphylococcus aureus, but may also be caused by Streptococcus viridans, or by Haemophilus influenzae, as well as viruses like mumps and HIV.
When it’s a bacterial infection, it often starts up after a salivary duct is plugged up by a salivary stone.
Salivary glands secrete saliva through tiny ducts in the mouth, to help lubricate the inside of the mouth and also moisten and soften food.
The antibacterial properties of saliva and the quick flow through the salivary duct both help to prevent infections from developing.
But there are various factors that reduce the rate of salivary flow, like dehydration, illness, and certain medications. These factors can allow deposits to settle in the walls of the salivary duct, physically blocking the path and further slowing down the flow of saliva.
This can allow tiny areas of stagnation where more deposits of calcium, phosphorous, and other electrolytes can precipitate out, ultimately forming small concretions called microsialoliths, or tiny salivary stones.
Over time, these can grow into sialoliths which are larger salivary stones.