Radiology Sialography and Salivary Glands Quiz

Salivary Glands

• Salivary glands are responsible for producing saliva
• The parotid gland is the largest major salivary gland.
• It is purely serous in nature.
• The parotid gland produces 30% of total saliva.
• Its main part is wedge-like, and it has a small deep part.
• The parotid (Stensen) duct is associated with the parotid gland.

Parotid Salivary Glands

• Lymphatic drainage begins within the parotid gland.
• Lymph then drains into preauricular or parotid lymph nodes.
• These nodes ultimately drain to the deep cervical chain.

Major Salivary Glands

• The parotid gland
• The submandibular gland
• The sublingual gland

Minor Salivary Glands

• Numerous, present in buccal, labial, palatal mucosa, tongue and floor of mouth.
• Mucous and secret continuously.
• Locations include palatine glands, sublingual glands, labial glands.

Submandibular Salivary Glands

• Mixed (mostly serous).
• Located between the mandible, mylohyoid muscle, and hyoid bone (occupying the submandibular fossa).
• Drains into the mouth via Wharton's duct.
• The duct has a forward and upward travel path.
• Produces 60% of saliva.

Sublingual Salivary Glands

• Under the tongue, below the floor.
• Produces 5% of saliva.
• Contains 10-20 small ducts; these open into the submandibular duct or directly into the floor directly.

Imaging of Salivary Glands

• Plain radiography is used to visualize stones and bone lesions.
• Sialography visualizes ductal structure, gland function, and obstructions.
• CT (computed tomography) assesses bone and soft tissue lesions.
• MRI (magnetic resonance imaging) is excellent for soft tissue masses.
• Scintigraphy (radioisotope imaging) assesses gland function.
• Ultra-sonography (US) is used to find soft tissues and vascular lesions.

Plain Radiography

• Illustrates sialoliths (stones).
• Shows bony involvement to rule out salivary gland diseases, and shows bony changes causing peri-auricular swelling.

Sialography

• Contrast agent introduced into the duct system.
• Scout view (PA or lateral oblique) determines exposure parameters, and is used to demonstrate radiopaque calculi and to detect extra-glandular and bone diseases.
• Materials needed for sialography include a lemon, contrast agent, a cannula, syringe, dilation, and wire.

Parotid Sialography

• Methods to perform sialography include orifice dilation, cannulation, media injection, lateral oblique, and PA views.

Sialography Technique

• Post-evacuation radiographs involve unstimulated and stimulated imaging.

Contraindications of Sialography

• Sensitivity to contrast agents.
• Acute sialadenitis.
• Obstruction in the distal 1/3 of duct.

Sialographic Interpretation

• Detailed knowledge of normal salivary gland radiographic appearance.
• Duct course and diameter, branching patterns, and uniform/gradual filling/emptying are analysed.
• Pathologic conditions are evaluated.

Normal Sialographic Appearance (Parotid)

• Main duct measures 1-2mm in diameter.
• Filling is uniform throughout the gland.
• Branching is gradual and in the style of a tree in winter.

Normal Sialographic Appearance (Submandibular)

• Main duct measures 3-4mm in diameter.
• Filling is uniform.
• Branching gradually, but is smaller than in the parotid.
• Shows a bush-like winter appearance.

Pathological Sialographic Appearance

• Sialolithiasis (salivary calculi) blockage in ducts or glands.
• Bacterial sialadenitis: acute or chronic bacterial infection of the terminal acini.
• Sialodochitis: inflammation in the duct system.
• Sialectasia: dilation of the salivary ducts.
• Sialosis (sialadenosis): non-neoplastic, non-inflammatory enlargement.

Sialographic Evidence of Salivary Gland Diseases

• Sialolithiasis: shows radiopaque or filling defects.
• Sialodochitis: shows segmental constriction and retained contrast agent.
• Sialadenitis: shows dilation of terminal ducts and retained contrast agent.
• Tumor: shows large filling defects, compression, or displacement.

Pathological Sialographic Appearance (detailed)

• Calculi (sialolithiasis) shows filling defects and ductal dilation.
• Retained contrast on emptying can also be seen in cases of sialolithiasis.
• The submandibular duct is commonly affected, and will show symptoms of sialolithiasis.

Submandibular Sialography

• Variations in methods include lateral views with subtraction, and lateral views of mandible.

Sialaduchitis

• Inflammation of the ductal system of SGs.
• Shows segmented sacculations and strictures of main duct (SAUSAGE appearance).
• Associated calculi or ductal stenosis may also be present

Sialectasia

• Seen by evaluating dilation of salivary ducts

Autoimmune Diseases

• Mikulicz's disease: bilateral hypertrophy of lacrimal and parotid salivary glands with no additional symptoms.
• Sjögren's syndrome: xerophthalmia (keratoconjunctivitis sicca), xerostomia (sicca syndrome) may be 1° or 2°; the latter occurs when associated with systemic CT disease such as Rheumatoid Arthritis, SLE, etc. benign lymphoepithelial lesions (BLELs) may form.

Sjögren's Syndrome

• Shows retention of contrast media inside gland indicating non-functioning gland

Autoimmune Sialadenitis

• Demonstrates punctate and spherical contrast agent collections that remain in gland after sialogogue.
• Later, larger pools of contrast (cavitary sialectases) will accumulate.

Mass Effect (Ball in Hand Appearance)

• Smoothly displaced duct around the mass (indicating mass in parotid gland).
• Sialography is of limited value in diagnosing intraglandular masses.

MRI

• Uses strong magnetic fields (typically 1.5 Tesla, converting 10,000 gauss). This is stronger than the Earth's magnetic field (0.5 Gauss).

Normal MRI Appearance (Parotid Gland)

• T1-weighted scans show intermediate-to-high signal intensity.
• T2-weighted scans show low-to-intermediate signal intensity.

Normal MRI Appearance (Submandibular Gland)

• T1-weighted scans show slightly lower signal intensity.
• T2-weighted scans show slightly higher signal intensity.

Coronal MRI

• Shows the nasopharynx, oropharynx, tongue, masseter, medial and lateral pterygoid muscles.
• It includes the mandibular ramus, parotid gland, and the submandibular gland.

Sagittal MRI

• Head of mandibular condyle and parotid gland can be seen in this view.

Axial MRI

• Mandibular condyle, maxillary sinus, external auditory canal, parotid gland, and external carotid artery can be observed in this view.

Cyst (Axial MRI)

• Images indicate the presence of cyst within a parotid area.

Axial CT

• Scans of parotid and submandibular glands show radiographic signs of pathologies.

Axial CT with Contrast

• Shows structures and anatomical features to help with diagnosis, such as mandible, sublingual gland, etc..

Parotid Hemangioma

• A hemangioma in the parotid gland can be observed radiographically.

Warthin's Tumor

• Axial and coronal sections show evidence of Warthin's tumor.

Pnuemo Parotid

• Images show air in the parotid duct and gland.
• Presence of air in ducts and gland.

Scintigraphy (Radioisotope Imaging)

• Assess saliva excretion, parotid gland, submandibular gland, and thyroid function.
• Measurements are taken at 0-5 min, 6-15 min, 16-20 min and 21-25 min; and acid (or stimulatory substances) are often involved and timed for these measurements.

Single-Photon Emission CT (SPECT)

• Images with CT, from 4 different views.

Ultrasound (US)

• Used to visually observe gland structure and tissues.

Inflammatory Salivary Gland Diseases

• Acute (e.g. Mumps)
• Chronic (e.g. Sjögren's syndrome)
• Sialolith, trauma, infection, space-occupying lesions

Non-inflammatory Salivary Gland Diseases

• Metabolic & secretory abnormalities
• Malnutrition
• Neurological disorders

Space-occupying masses

• Cysts
• Neoplastic: Benign and Malignant

DDx of SG tumor

• 80% of salivary gland tumors are in parotid. 70-80% in superficial lobe
• Most are benign or low-grade
• Incidence of benign SG tumors increases with gland size
• Pleomorphic adenoma accounts for 75% of SG tumors
• 80% of pleomorphic adenomas in the parotid, 4% in submand, 1% in sublingual and 10% in minor glands
• Hemangioma is most common during infancy and childhood.

Pleomorphic Adenoma

• Sharp, circumscribed, homogeneous, low-signal oval mass in posterior medial parotid gland in T1 weighted MRI axial view.

DDx of Enlargements in the Parotid Area (Unilateral)

• Bacterial sialadenitis
• Sialodochitis
• Cysts
• Benign neoplasms
• Malignant neoplasms
• Intraglandular lymph nodes
• Masseter muscle hypertrophy
• Lesions in adjacent osseous structures

DDx of Enlargements in the Parotid Area (Bilateral)

• Bacterial sialadenitis
• Viral sialadenitis (mumps)
• Autoimmune diseases (Sjögren's Synd., Mikulicz, BLELs)
• Warthin's tumor
• Alcoholic hypertrophy
• Medication-induced conditions (iodine, heavy metals)
• HIV-associated multicentric cysts
• Masseter muscle hyperplasia
• Accessory salivary glands
• TMJ-related lesions
• Radiation therapy

DDx of Enlargements in the Submandibular Area (Unilateral)

• Bacterial sialadenitis
• Sialodochitis
• Fibrosis
• Cysts
• Benign neoplasms
• Malignant neoplasms
• AV malformation

DDx of Enlargements in the Submandibular Area (Bilateral)

• Bacterial sialadenitis
• Autoimmune sialadenitis
• Lymphadenitis
• Brachial cleft cysts
• Submandibular space infection

Mumps

• Most common cause of acute painful parotid swelling in children.
• Caused by paromyxovirus.
• Flu-like symptoms followed by bilateral painful parotid swelling.
• Resolves spontaneously in 5-10 days.
• Can be unilateral in some cases.
• Sometimes affects submandibular glands.