Scanning Method: Continuous longitudinal and transverse scanning of the parotid gland region is performed with patient supine (posterior part of the face, inferior to the zygomatic arch, anterior and inferior to the external auditory meatus, anterior to the mastoid process, superficial to the masseter muscle, posterior to the ramus and angle of mandible); jugular lymph nodes should also be examined at the same time.
Section Structure :Anterior border of the parotid gland is clear, echogenicity of the parotid parenchyma is homogenous with the echogenic dense higher than the adjacent soft tissue. Posterior and lateral borders are usually unclear because of the attenu ation of the parotid parenchyma. The longitudi nal section of the parotid gland is of pyramid shape. Superficial and profound lobe cannot be differentiated from the image. The normal parotid duct cannot be shown in the image.
Measurement Method and Normal Value: On ultrasound, the parotid gland measures approximately 40 to 60 mm in length along its long axis, although variations may occur depending on age, sex, and body habitus. The gland appears as an elongated, somewhat triangular or wedge-shaped structure in longitudinal scans, with homogeneous echotexture that is slightly hyperechoic compared to adjacent muscle.
Normal Size Range of the Parotid Gland by Age: The parotid gland demonstrates age-related variations in size and echotexture. In general, the gland grows rapidly in early childhood, reaches stable adult dimensions in adolescence, and may show fatty infiltration or atrophy in elderly individuals.
| Age Group | Normal Longitudinal Length (cm) | Normal Thickness (cm) | Remarks |
|---|---|---|---|
| Infants (0–1 yr) | 2.0 – 3.0 | 0.8 – 1.2 | Rapid growth; echotexture relatively hypoechoic. |
| Children (2–10 yrs) | 3.0 – 4.0 | 1.0 – 1.5 | Progressive enlargement; homogeneous echotexture. |
| Adolescents (11–18 yrs) | 4.0 – 5.0 | 1.2 – 1.8 | Adult size reached; echotexture brighter than muscle. |
| Adults (19–60 yrs) | 4.0 – 6.0 | 1.5 – 2.0 | Stable dimensions; homogeneous, lobulated appearance. |
| Elderly (>60 yrs) | 3.5 – 5.5 | 1.2 – 1.8 | May show fatty infiltration, atrophy, or heterogeneity. |
Note: Anterior-posterior length cannot be measured because of the blurred margin. Profound group of the parotid lymph nodes is located in the parotid parenchyma and should not be misdiagnosed as focal lesion of the parotid gland.
Measurement Technique: For accurate assessment, the linear transducer is aligned parallel to the long axis of the gland, extending from the preauricular region down to the mandibular angle. The maximal length is measured from the superior to the inferior margin, ensuring the probe orientation is correct to avoid underestimation.
Clinical Importance: Assessing the longitudinal length of the parotid gland is important in cases of suspected gland enlargement (parotitis, sialadenosis, neoplastic lesions) or atrophy. A comparison with the contralateral gland is essential to evaluate asymmetry. Increased longitudinal dimension often correlates with acute or chronic inflammatory swelling, while focal enlargement may suggest space-occupying lesions.
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