What are the characteristic ultrasound findings of a ranula?

Ultrasound Findings of Ranula

Ranulas typically appear as well-defined, anechoic or hypoechoic cystic lesions in the floor of the mouth, with characteristic features that help differentiate them from other sublingual or submandibular lesions.

Types and Locations

• Ranulas are mucous extravasation or retention cysts derived from the sublingual or submandibular salivary glands 1
• Two main types exist:
  • Simple ranula: Limited to the floor of the mouth, presenting as a superficial cystic mass 1
  • Plunging (diving) ranula: Extends through facial planes, usually posterior to the mylohyoid muscle into the neck, presenting as a cervical mass 1, 2

Key Ultrasound Characteristics

• Ranulas appear as well-defined, thin-walled cystic lesions with the following features:
  • Anechoic or hypoechoic internal content 2
  • Homogeneous internal echoes 2
  • Posterior acoustic enhancement (typical of fluid-filled structures) 2
  • Absence of internal vascularity on color Doppler imaging 2

Specific Findings in Plunging Ranulas

• High-resolution ultrasound can effectively determine the extent of plunging ranulas 2
• Characteristic findings include:
  • Cystic collection in the submandibular space (identified in 96.7% of cases) 2
  • Defect in the mylohyoid muscle (demonstrated in 90-100% of cases) 2
  • Evidence of sublingual gland rupture or herniation 2
  • Extension through the mylohyoid muscle into the submandibular and cervical spaces 2

Diagnostic Value of Ultrasound

• Ultrasound is highly accurate in confirming the cystic nature of ranulas 2
• It can reliably differentiate ranulas from solid masses in the floor of the mouth 2
• Excellent correlation between ultrasound findings and surgical observations has been reported 2
• Ultrasound is particularly valuable for:
  • Assessing the status of the mylohyoid muscle 2
  • Evaluating the sublingual gland for rupture or herniation 2
  • Determining the extent of plunging ranulas 2

Differential Diagnosis Considerations

• Ultrasound helps differentiate ranulas from other cystic lesions in the neck and floor of mouth, including:
  • Thyroglossal duct cysts 1
  • Branchial cleft cysts 1
  • Cystic hygromas 1
  • Submandibular sialadenitis 1
  • Intramuscular hemangiomas 1

Clinical Correlation

• Ultrasound findings should be correlated with clinical presentation:
  • Painless, slow-growing, soft, and movable mass in the floor of the mouth 1
  • In plunging ranulas, a cervical mass may be the primary presentation 1, 3
  • Unusual presentations may include extension to the vallecula, which can be mistaken for a vallecular cyst 3

Recommendations for Imaging

• Ultrasound is recommended as the preferred initial examination for suspected ranulas due to:
  • Cost-effectiveness 2
  • Accessibility 2
  • Lack of radiation exposure (important as many patients are young, with a median age of 20 years) 2
  • High diagnostic accuracy 2
• For atypical presentations or when planning surgical intervention, MRI may provide additional information about the extent of the lesion 3