Longitudinal Scan of the Submandibular Gland

Definition — Longitudinal Scan of the Submandibular Gland: An ultrasound technique where the transducer is aligned parallel to the long axis of the submandibular gland, usually placed in the submandibular region below the mandible. This view demonstrates the gland as an elongated, elliptical structure with homogeneous echotexture, slightly hyperechoic relative to adjacent muscles. Wharton’s duct may be visualized as a thin hypoechoic tubular structure extending anteriorly. The longitudinal scan also depicts surrounding anatomical landmarks including the mylohyoid and digastric muscles, mandibular border (echogenic with acoustic shadowing), adjacent vessels (facial artery/vein), and regional lymph nodes when present.

Scanning mathod: The patient takes a supine position and extends the neck adequately. Probe Placement Place the linear high-frequency transducer in the submandibular region, just below the angle of the mandible, oriented parallel to the long axis of the gland (sagittal orientation). The probe marker should point anteriorly toward the patient’s chin. Gentle angulation superiorly and inferiorly allows full visualization of the gland, Wharton’s duct, and adjacent anatomical structures. Minimal pressure is advised to avoid compressing the gland or duct.

Section Structure: Submandibular gland is oval shaped with clear borders. The parenchymal echo character is the same to that of the parotid gland; echo density is higher than adjacent soft tissue and without pos terior attenuation. Facial artery sometimes can be shown in the gland. The normal submandibular duct cannot be shown in the image.
1. Subcutaneous fatt
2. LN- Lymph Node
3. SMG- Submandibular Gland
4. FA- Facial Artery

Measuring mathod and normal value: Longitudinal diameter and thickness can be mea sured on this section. The mean longitudinal diameter and thickness are 30mm and 1.5 mm and there is no significant difference between male and female.

Parameter	Measuring Method	Normal Value
Length (Long Axis)	Measured in longitudinal (sagittal) scan from anterior to posterior poles	30 – 40 mm
Width (Transverse)	Measured in transverse scan at widest portion	10 – 15 mm
Thickness (AP Dimension)	Measured anteroposteriorly in longitudinal scan	7 – 10 mm
Volume	Calculated using formula: Length × Width × Thickness × 0.52	~ 6 – 8 cm³ (adults)

Age Group	Length (mm)	Width (mm)	Thickness (mm)	Volume (cm³)
Neonates / Infants	10 – 20	5 – 8	3 – 5	~ 0.3 – 0.8
Children (2 – 10 yrs)	20 – 30	8 – 10	4 – 6	~ 1 – 3
Adolescents (11 – 18 yrs)	25 – 35	9 – 12	5 – 7	~ 3 – 5
Adults (≥ 19 yrs)	30 – 40	10 – 15	7 – 10	~ 6 – 8
Elderly (> 65 yrs)	28 – 38	9 – 13	6 – 9	~ 5 – 7 (may decrease due to fatty atrophy)

Common Pathologic Findings — Submandibular Gland:

1. Sialadenitis (Inflammation)
• Acute: Enlarged, hypoechoic gland, increased vascularity (Doppler).
• Chronic: Heterogeneous echotexture, reduced vascularity, atrophic changes.

2. Sialolithiasis (Ductal Calculi)
• Echogenic focus within Wharton’s duct or gland parenchyma.
• Posterior acoustic shadowing; ductal dilatation proximal to stone.

3. Neoplastic Lesions
• Benign: Pleomorphic adenoma (well-defined, hypoechoic, homogeneous).
• Malignant: Irregular, poorly defined, heterogeneous, possible infiltration of adjacent tissue.

4. Cysts
• Anechoic, well-defined lesion with posterior acoustic enhancement.
• May be congenital (ductal cysts) or acquired (post-inflammatory).

5. Abscess
• Hypoechoic/complex fluid collection, irregular walls, increased peripheral vascularity.
• Often associated with cellulitis or sialadenitis.

6. Lymphadenopathy
• Reactive: Oval nodes with preserved fatty hilum.
• Suspicious: Round nodes, loss of hilum, peripheral/chaotic vascularity.

7. Autoimmune Disorders
• (e.g., Sjögren’s syndrome) — Enlarged, heterogeneous gland with multiple small hypoechoic areas (“salt and pepper” or “honeycomb” pattern).

8. Trauma / Post-surgical Changes
• Heterogeneous echotexture, scar tissue, or hematoma depending on stage.