Ranulas are a specific type of mucocele, a fluid-filled lesion that appears as a swelling on the floor of the mouth. The name comes from the Latin word rana (frog), as a large ranula can resemble the underbelly of a frog. This lesion originates most often from the sublingual gland and is filled with mucus that has leaked into the surrounding tissues. A common question is whether the body will reabsorb the fluid naturally or if medical intervention is necessary. This article examines the formation of these cysts and the likelihood of them disappearing without treatment.
Defining Ranulas and Their Causes
Ranulas are defined by their location in the sublingual space, where the sublingual salivary gland resides. The formation begins when the normal flow of saliva is disrupted, causing mucus to pool and accumulate.
The most common mechanism is mucus extravasation, where trauma causes a tear in the salivary duct. This rupture allows mucin to spill into the surrounding connective tissue, forming a collection known as a pseudocyst, which lacks a true epithelial lining. Less frequently, a ranula forms due to mucus retention when a salivary duct is partially obstructed by a foreign body or a mucus plug. In this case, the duct dilates, creating a true cyst lined with epithelial cells.
A ranula often presents as a soft, translucent, bluish swelling located to one side of the midline under the tongue. While usually painless, a large lesion can interfere with speech, swallowing, or the fitting of dentures. The size and location of the lesion determine its classification and prognosis.
When Ranulas Resolve on Their Own
Spontaneous resolution of a ranula is possible but remains an uncommon outcome for most lesions. Small, simple ranulas confined to the sublingual space have the highest chance of resolution, especially in infants with congenital lesions. The body may reabsorb the collected fluid, or the pseudocyst wall might rupture and drain on its own.
Even when a ranula resolves naturally, the underlying cause—the damaged or blocked salivary duct—often remains, leading to a high frequency of recurrence. For small, asymptomatic lesions, a period of watchful waiting may be appropriate for a few weeks to months. This observational period is not recommended for large or symptomatic lesions that interfere with eating or breathing.
A plunging ranula, also known as a cervical or diving ranula, extends downward into the neck through a defect in the mylohyoid muscle. These lesions present as a swelling in the neck rather than the floor of the mouth. Plunging ranulas almost never resolve without medical intervention because the continuous mucus accumulation demands active treatment for permanent resolution.
Surgical and Non-Surgical Treatment
When a ranula is persistent, large, or causes functional problems, active treatment is necessary to prevent continued mucus accumulation. Non-surgical options, such as needle aspiration, involve draining the fluid, but the recurrence rate is nearly 100% because the mucus source is not addressed. Sclerotherapy involves injecting a substance like OK-432 into the cyst to induce scarring. While some trials report success rates nearing 90%, sclerotherapy often requires multiple treatments and may not be suitable for large or plunging ranulas.
Surgical intervention provides the most reliable long-term solution, and the technique chosen depends on the ranula’s size and type. For simple oral ranulas, marsupialization is a common procedure. The cyst’s roof is removed, and the edges are sutured to the adjacent oral mucosa to create a pouch. This allows the contents to drain freely into the mouth, making the cyst less likely to re-accumulate fluid. However, simple marsupialization has a high recurrence rate, sometimes exceeding 60%, due to premature closure of the opening.
The most definitive treatment, particularly for plunging or recurrent oral ranulas, is the complete excision of the ipsilateral sublingual gland. Removing the sublingual gland, the mucus-producing source, drastically reduces the likelihood of the ranula returning. Reviews of surgical outcomes show that removing the ranula along with the entire sublingual gland results in the lowest recurrence rates, typically falling between 1.2% and 3.8%. This approach targets the root cause of the mucus extravasation, making it the preferred method for long-term resolution.