Stensen’s Duct, or the Parotid Duct, drains saliva from the parotid gland, the largest salivary gland, into the mouth. A clear channel is necessary for the proper flow of saliva, which is required for digestion and oral health. Dysfunction of this duct can lead to a backup of fluid, resulting in pain, swelling, and potential infection.
Anatomical Placement and Physiological Role
Stensen’s Duct begins at the parotid gland, located near the ear and extending toward the jaw. This relatively narrow tube measures approximately 7 centimeters (2.76 inches) in length. It runs horizontally across the outer surface of the masseter muscle in the cheek.
The duct turns inward, piercing the buccinator muscle, which forms the inner wall of the cheek. Stensen’s Duct opens into the oral cavity through the parotid papilla, a small elevation of tissue. This opening is located on the inner cheek surface, opposite the crown of the second upper molar tooth.
The duct transports the parotid gland’s saliva into the mouth. Parotid saliva is watery and rich in amylase, an enzyme that initiates starch digestion. Although output is small at rest, it increases significantly when stimulated by the sight, smell, or taste of food. A functioning duct ensures this enzyme-rich fluid reaches the mouth to aid in lubrication and the initial breakdown of food.
Sialolithiasis
Sialolithiasis is the formation of calcified masses, or stones, within the salivary gland or its ductal system. In Stensen’s Duct, these stones create a physical blockage preventing the free flow of saliva. Although the submandibular gland is the most common site, Stensen’s Duct is the second most common location for salivary stones.
The presence of a stone typically causes a cyclical pattern of pain and swelling in the cheek. This swelling is pronounced during or shortly after eating, known as “mealtime syndrome.” Eating stimulates the parotid gland to produce saliva, which backs up behind the obstruction, causing the gland to engorge and swell.
The stones are primarily composed of calcium phosphate, along with smaller amounts of magnesium and carbonate. Risk factors include dehydration, reduced food intake, and the use of certain medications, such as anticholinergics. These factors can lead to salivary stasis, creating an environment where salts precipitate and form a stone.
Conservative management encourages the stone to pass spontaneously by increasing salivary flow. Patients are encouraged to maintain good hydration and use sialogogues, such as sour candies or lemon wedges, to stimulate saliva production. Applying gentle massage to the affected gland may also help manipulate the stone toward the duct opening.
Related Infections and Narrowing
Stensen’s Duct is susceptible to infections and narrowing that compromise salivary flow. Sialadenitis, an infection of the parotid gland, frequently occurs when the duct is blocked, causing saliva to stagnate. This stagnant environment allows bacteria to multiply and ascend into the gland.
Symptoms of bacterial sialadenitis include pain, swelling, fever, and the drainage of pus from the duct’s opening. While blockage is a common trigger, viral infections like mumps can also cause acute parotitis, leading to generalized swelling and inflammation of the gland.
Strictures are segments of narrowing within the duct caused by the formation of fibrous tissue in the duct walls. This often results from trauma, chronic inflammation, or previous infections. When the duct narrows, saliva outflow is impaired, leading to recurrent swelling similar to that caused by stones.
Strictures are the second most common cause of chronic obstructive sialadenitis when stones are absent. The parotid duct system is prone to stricture formation due to its relatively superficial course and narrower baseline diameter. Chronic inflammation and underlying autoimmune diseases are also associated with these narrowings.
Diagnostic Techniques and Treatment Approaches
Diagnosis of Stensen’s Duct problems combines physical examination and advanced imaging. Palpation of the cheek can reveal an enlarged or tender gland, and visual inspection may show swelling near the duct’s opening. Non-invasive imaging techniques are used to confirm the presence and location of an obstruction.
Ultrasound visualizes the duct and gland, detecting stones and signs of inflammation. Computed Tomography (CT) scans and specialized Magnetic Resonance (MR) sialography offer detailed cross-sectional images. These techniques pinpoint the exact location and size of a stone or the extent of a ductal narrowing.
Sialendoscopy is the current standard for both diagnosis and minimally invasive treatment. This procedure uses a micro-endoscope, a narrow tube inserted directly into the duct opening. Sialendoscopy allows for direct visualization of the ductal system, enabling doctors to classify the obstruction as a stone, mucus plug, or fibrous stricture.
Sialendoscopy-guided treatment is gland-preserving and involves minimally invasive interventions. For small stones, tiny baskets or graspers retrieve the stone through the endoscope. For strictures, the endoscope guides the dilation of the narrowed segment, restoring normal saliva flow. Traditional open surgery, which carries a higher risk of nerve damage, is reserved for very large, deeply impacted stones or when minimally invasive methods fail.