Final answer:
The most likely cause of the symptoms described is acute bacterial sialadenitis, which is characterized by inflammation and infection of the salivary gland.
Step-by-step explanation:
The most likely cause of a patient with pain, fever, and unilateral parotid swelling following a general anesthetic is acute bacterial sialadenitis.
This condition is characterized by the inflammation and infection of the salivary gland, which can be caused by bacteria entering the gland through the salivary duct. General anesthesia can sometimes result in reduced salivary flow, which can increase the risk of bacterial infection in the gland. Symptoms of acute bacterial sialadenitis include pain, swelling, and fever.
It is important for the patient to seek medical attention for a proper diagnosis and appropriate treatment.