Define Ranula. Describe its clinical features, management and pathogenesis.

The Concept

A ranula is a mucous (retention/extravasation) cyst arising in the floor of the mouth from the sublingual salivary gland (or occasionally the submandibular duct). The name comes from the Latin for 'little frog' (rana), because the translucent swelling under the tongue resembles a frog's belly. It forms when a sublingual duct is obstructed or damaged and mucus collects or leaks into the surrounding tissue.

Clinical Features

The typical ranula is a soft, cystic, bluish, translucent swelling in the floor of the mouth to one side of the midline, lifting the tongue. It is usually painless but can interfere with speech and eating as it enlarges. An important variant is the 'plunging ranula', which extends downwards through (or around) the mylohyoid muscle to present as a swelling in the neck — so a neck swelling with an intra-oral component may be a plunging ranula.

Management

Treatment options are marsupialisation (deroofing the cyst and suturing its edges open) for simple lesions, or, because of a tendency to recur, excision of the ranula together with the sublingual gland for definitive cure, especially for recurrent or plunging ranulas.

Differential

The differential of a swelling in the floor of the mouth includes a sublingual dermoid, a submandibular duct stone with obstruction, and a plunging ranula presenting in the neck; the bluish translucent appearance and relation to the sublingual gland point to a ranula, confirmed at surgery.

Pathogenesis

The common (simple) ranula is a mucous extravasation cyst — saliva leaks from a damaged sublingual duct and pools, walled off by granulation tissue rather than a true epithelial lining. The plunging variety occurs when this collection herniates through or around the mylohyoid muscle into the neck. Understanding that the sublingual gland is the source explains why definitive treatment often involves removing that gland, not just the cyst, to prevent recurrence.

Management Decisions

Treatment is tailored to the type: a small simple ranula may be watched or marsupialised, but because marsupialisation has a high recurrence rate, definitive management of recurrent or plunging ranulas is excision of the ranula together with the sublingual gland. A plunging ranula presenting as a neck lump is confirmed on imaging (MRI) showing its connection through mylohyoid to the sublingual space, so that the neck swelling is correctly attributed and treated at its oral source.

The Bottom Line

In summary, the ranula is a sublingual mucous cyst — bluish and translucent in the floor of the mouth, or 'plunging' through mylohyoid into the neck — cured most reliably by excision together with the sublingual gland, marsupialisation being simpler but more prone to recurrence.

A plunging ranula extends below the mylohyoid into the neck.

• Ranula = mucous extravasation/retention cyst of the floor of the mouth from the sublingual gland.
• Soft, cystic, bluish, translucent swelling under the tongue ('little frog belly'); may impair speech/eating.
• 'Plunging ranula' extends through mylohyoid to present as a neck swelling.
• Treat by marsupialisation, or excision with the sublingual gland (definitive; for recurrent/plunging types).