parotid gland- normal
for normal anatomy and scanning protocol
scan plane
the parotid will be seen wrapping around the angle of the mandible up to the tragus of the ear. an extension of the gland or accessory parotid lies medially on the cheek and is the landmark for the parotid duct.
an accessory parotid gland can sometimes be seen just medial to the main parotid gland. this is the scan plane to visualise it.
normal parotid gland.
note the high attenuation which is secondary to normal fatty infiltration of the parotid. if, as in this case you cannot visualise the deep margin, use a lower frequency transducer. even a curvilinear may be required.
the attenuation of the parotid may obscure the deep border. use a lower frequency probe to check for any deep lesions.
the arrow shows the clear deep border that is not visible on the prior image.
normal parotid gland.
note the high attenuation which is secondary to normal fatty infiltration of the parotid. if, as in this case you cannot visualise the deep margin, use a lower frequency transducer. even a curvilinear may be required.
a normal lymph-node embedded within the parotid gland.
the parotid gland is far more attenuative than the submandibular gland and may contain embedded lymphnodes. the submandibular gland forms earlier embryologically and should never contain other tissue.
normal ultrasound of the accessory parotid. this is the best landmark to identify the parotid (stensen) duct.
the blue arrows indicate the approximate position of the parotid duct as it exits the parotid in the cheek, prior to diving towards it’s ampulla.
normal ultrasound of the accessory parotid still joined to the main body of the parotid gland by an isthmus.
the blue arrows indicate the approximate position of the parotid duct as it exits the parotid in the cheek, prior to diving towards it’s ampulla.
highlighted anatomy.
scan protocol
role of ultrasound
intraglandular and extraglandular lesions to be localised and differentiated.
to identify the cause of:
- a lump in the gland/neck. the patient can sometimes palpate a stone under the mandible.the stone can block the duct causing infection and swelling.
- pain
- mumps
- illness, including mouth or dental infections
- mouth dryness
- abnormality on previous xrays, ct or sialogram
- guidance of injection, aspiration or biopsy
limitations
- facial hair (will require a lot of gel)
- bulky parotid (may require a curvilinear probe to penetrate to the deep border)
- the distal most duct and ampulla cannot be seen in the normal patient. to visualise the ampulla in an obstructed duct try asking the patient to distend their cheek with a mouthful of water. the water will outline the ampulla.
patient preparation
- low collared shirt
- may have to remove jewellery
- towel across the chest/shoulders
- lie the patient so their head is at the top of pillow and neck extended.
- a pillow or towel can be placed under the shoulders
equipment setup
- use of a high resolution 7-14mhz linear transducer. you may need to use a lower frequency or curved linear probe (5-7mhz) to visualise the deep portion of the submandibular or parotid glands.
- good colour / power / doppler capabilities when assessing vessels or vascularity of a structure.
- be prepared to change frequency output of probe (or change probes) to adequately assess both superficial and deeper structures.
common pathology
- parotitis
- cysts
- adenoma
- adenocarcinoma
- calculus
- sialectasis
embedded lymph nodes are common and a normal finding. ensure the lymph nodes are morphologically normal. primary lymphoma of the parotid is rare. metastatic spread to the parotid and submandibular glands may occur.
scanning technique
- tip the patient’s head back for better access.
- assess the gland’s echogenicity. it should be hypoechoic with a homogeneous echotexture compared to the surrounding tissue, similar to a muscle’s echogenicity.
- due to it’s fat content, the parotid will be more attenuative than the submandibular gland.
- compare both sides if necessary.
- scan the entirety of the gland from midline to lateral several times to assess :
- the size
- for increased vascularity
- any abnormality in the surrounding anatomy including the lymph nodes.
- duct dilatation (use colour doppler so you do not mistake a vessel to be a dilated duct)
- the parotid duct runs from the deep gland to the ampulla adjacent to the upper 2nd molar tooth.
- the duct starts from the level of the ear-lobe and courses across the cheek via the accessory parotid gland. the duct generally will not be visible unless dilated.
- the kuttner lymph node is a normal, prominent lymph node between the parotid and submandibular gland.
basic hardcopy imaging
a salivary gland series should include the following minimum images:
- submandibular gland, long & trans
- submandibular duct
- parotid gland, long & trans
- accessory parotid gland
- right side of the neck and lymph nodes
- left side of the neck and lymph nodes
- document the normal anatomy. any pathology found in 2 planes, including measurements and any vascularity