A ranula is a soft, fluid-filled cyst or swelling that appears beneath the tongue on the floor of the mouth. This lesion is benign (not cancerous) and develops when the flow of saliva is disrupted.
Anatomy of the Ranula: Location and Origin
The formation of a ranula is directly linked to the sublingual gland, the smallest of the three major pairs of salivary glands. This gland is situated in the floor of the mouth, beneath the tongue and above the mylohyoid muscle. It continuously produces predominately mucous saliva. The sublingual gland releases this saliva into the oral cavity through multiple small ducts known as the ducts of Rivinus.
The Physical Mechanisms of Formation
Ranulas develop due to a disruption in the normal pathway of saliva flow from the sublingual gland.
Mucus Extravasation
The most frequent cause is mucus extravasation, which occurs when a salivary duct ruptures, allowing mucus to leak into the adjacent soft tissue. This rupture is often spontaneous or the result of minor, unnoticed trauma, such as biting or injury during a dental procedure. The escaped mucus then triggers an inflammatory response, leading to the formation of a pseudocyst that lacks a true epithelial lining.
Mucus Retention
A less common mechanism is mucus retention, where the salivary duct becomes completely blocked or obstructed. This blockage, perhaps from a mucus plug, scarring, or a small stone (sialolith), causes saliva to back up within the duct and the gland itself. The pressure from the retained saliva causes the duct to swell and balloon, forming a true retention cyst that is lined with epithelial cells.
Two Categories of Ranula: Oral vs. Plunging
Ranulas are categorized into two types based on their physical location, determined by how the escaped mucus spreads through the surrounding anatomy.
Oral Ranula
The simpler and more common type is the Oral Ranula, which remains confined to the sublingual space above the mylohyoid muscle. These lesions typically appear as a translucent, bluish, dome-shaped swelling directly under the tongue. They are often asymptomatic unless they grow large enough to interfere with speech or swallowing.
Plunging Ranula
The second, more complex type is the Plunging Ranula, also known as a cervical or diving ranula, which extends downward into the neck region. This occurs when the escaped mucus dissects through a defect or natural opening in the mylohyoid muscle, traveling into the submandibular or cervical spaces. A plunging ranula presents as a soft, mobile, and often painless swelling in the upper neck, sometimes with no visible swelling remaining in the mouth.
Medical Interventions for Resolution
Treatment for a ranula is typically surgical, especially if the lesion is large, symptomatic, or recurrent.
Marsupialization
One common approach, particularly for smaller oral ranulas, is Marsupialization. This procedure involves incising the ranula and suturing the edges of the cyst lining to the oral mucosa, opening the cyst for continuous drainage. However, marsupialization has a relatively high recurrence rate, sometimes exceeding 40%, because the underlying source of the mucus remains intact.
Complete Excision
A more definitive treatment is the Complete Excision of the ranula along with the entire ipsilateral sublingual gland. Removing the gland eliminates the source of the mucus, which drastically reduces the risk of the ranula recurring to as low as 2%. This approach is often considered the standard of care for plunging ranulas due to their complexity and high likelihood of recurrence with less aggressive methods. While simple aspiration of the fluid is possible, it is not recommended as a standalone treatment due to recurrence rates often higher than 80%.