Ranula

A ranula is a mucous extravasation pseudocyst arising from the sublingual gland or, less commonly, a minor salivary gland within the floor of the mouth. It results from ductal disruption and extravasation of mucus into the surrounding soft tissue.

It is classified as simple (confined entirely within the floor of the mouth, above the mylohyoid muscle) or plunging (also termed diving).

In a plunging ranula, mucus extends through or around the mylohyoid muscle into the submandibular or, less commonly, more distant neck spaces. This produces a distinct neck swelling in addition to, or occasionally without, an obvious intraoral component.

This anatomical distinction directly informs the surgical approach.

Pathophysiology

• Disruption of the sublingual gland duct, from trauma, obstruction or an unclear, spontaneous cause, allows mucus to extravasate into the soft tissue of the floor of the mouth.
• The resulting collection lacks a true epithelial lining, which makes it a pseudocyst rather than a true cyst.
• The pattern of extravasation determines whether the swelling stays above the mylohyoid muscle (simple ranula) or extends through or around it into the neck (plunging ranula).

• A simple ranula presents as a soft, fluctuant, bluish, translucent swelling within the floor of the mouth, typically lateral to the midline (reflecting its sublingual gland origin).
• It is often likened in appearance to a frog's underbelly, from which the condition derives its name. It is generally painless unless secondarily infected or traumatised.
• A plunging ranula presents with a soft, fluctuant neck swelling, typically in the submandibular or upper cervical region. It may occur with or without a visible intraoral component.
• If the intraoral, sublingual component is not specifically identified on examination, it can be confused with other causes of neck swelling, particularly congenital neck masses.

• Diagnosis is generally clinical, based on the characteristic appearance and location.
• Ultrasound supports confirmation and characterisation of the extent of the lesion. Magnetic resonance imaging is used for more complex or plunging lesions, where precise delineation of the extent of extension is required for surgical planning.
• Imaging is particularly important for distinguishing a plunging ranula from other causes of neck swelling and for guiding the surgical approach.
• Aspiration, where performed, characteristically yields thick, mucoid fluid, which supports the diagnosis.
• Aspiration alone is not generally curative, given the high recurrence rate without addressing the underlying, disrupted sublingual gland.

• Marsupialisation (surgical unroofing of the lesion, allowing continued drainage while the surrounding tissue heals and epithelialises around the opening) is a treatment option.
• It carries a relatively high recurrence rate, particularly for larger or plunging lesions, because the underlying, disrupted sublingual gland remains the continuing source of mucus extravasation.
• Excision of the sublingual gland addresses the source directly. It is the definitive, most effective treatment with the lowest recurrence rate.
• Gland excision is generally the preferred approach, particularly for plunging ranula or for recurrent simple ranula after an initial, less definitive treatment.
• Plunging ranula requires careful surgical planning given the potential extent of the cervical component. Standard definitive surgery is sublingual gland excision, combined with drainage or excision of the cervical mucus collection where required.
• Regular follow up confirms resolution and monitors for recurrence. This is particularly important given the recognised recurrence risk with marsupialisation alone.