Analysis of causes for non-stone parotid obstructions

Parotid obstructions can cause repeated swelling of the glands. Previously, duct stones were thought to be the main cause of obstructions, but salivary gland endoscopy examinations have revealed the absence of stones or foreign bodies in the duct system of the parotid glands with obstructive symptoms. Diseases of the parotid gland with obstructive symptoms include chronic recurrent parotitis, non-stone chronic obstructive parotitis, Sjögren′s syndrome, IgG4-related parotitis and radiation-induced parotitis. The mechanism of obstructions is unknown, and the disease course is prolonged. In this paper, based on a brief analysis of duct stenosis, distortion and mucus emboli, which may lead to parotid obstructions, a new perspective is emphasized: the duct system of the parotid and flowing saliva constitute a microflow field. Based on the principle of fluid mechanics, the flow of saliva in the flow field can be affected by the confluence, diameter changes, and twist of the ducts. This outcome results in changes in the low velocity zone, backflow, counterflow and turbulence; affects saliva flow and normal discharge; and causes symptoms of parotid obstruction. An analysis of the possible mechanisms of parotid obstruction using two variables, duct anatomy and saliva traits, helps explain the causes of nonstone parotid obstructions.