A ranula is a soft, fluid-filled swelling that forms in the floor of the mouth when saliva leaks out of a damaged or blocked salivary gland and pools in the surrounding tissue. It typically appears as a painless, bluish, translucent bump under the tongue, and its name comes from the Latin word “rana” (frog) because it resembles a frog’s belly. Ranulas originate from the sublingual gland in about 90% of cases, though they can occasionally involve the submandibular gland.
Simple vs. Plunging Ranulas
Ranulas fall into two categories based on how far they extend. A simple ranula stays confined to the sublingual space, the area directly beneath the tongue. It shows up as a round or oval, bluish swelling on the floor of the mouth that you can see when you open wide or lift your tongue. Most people notice it as a soft, painless lump that slowly grows over time.
A plunging ranula is less common and more complex. Instead of staying under the tongue, the collected saliva pushes past the mylohyoid muscle (the muscular floor that separates your mouth from your neck) and extends downward into the neck. This can happen through a natural gap in the muscle or around its back edge. The result is a painless swelling on the side of the neck that doesn’t move when you swallow. Most plunging ranulas still have a visible bluish component under the tongue, which helps distinguish them from other neck masses. A South Auckland population study found plunging ranulas occur at an annual rate of roughly 2.4 per 100,000 people, with slightly higher rates in males.
What Causes a Ranula
The underlying problem is disrupted saliva flow. The most common trigger is trauma to the sublingual gland or its ducts, whether from an accidental bite, dental work, or another injury. When a duct is damaged, saliva escapes into the tissue instead of draining normally into the mouth. This leaked mucus accumulates and forms a pocket called a pseudocyst, meaning it lacks the true lining of a standard cyst.
Blockages can also be the culprit. A salivary stone, scar tissue around a duct, or even a tumor can obstruct the outflow of saliva and cause it to back up. Some people have anatomical variations in their duct system that make them more prone to developing a ranula. Specifically, when one of the sublingual ducts connects to and empties into the main submandibular duct, the risk appears to increase.
What a Ranula Looks and Feels Like
A typical ranula presents as a gradually enlarging, dome-shaped swelling on one side of the floor of the mouth. It has a characteristic bluish, translucent appearance because the thin tissue covering it allows the trapped mucus to show through. On touch, it feels soft, fluctuant (like pressing a water balloon), and painless. The swelling is usually well-defined with clear borders.
In many cases, a ranula causes no symptoms beyond the visible lump. Smaller ones may go unnoticed for a while. Larger ones can push the tongue upward or to one side, and in some cases may interfere with eating or speaking, though many patients report no difficulty with either. Plunging ranulas add a painless, compressible mass on the front or side of the neck that can be more cosmetically noticeable than functionally problematic.
How Ranulas Are Diagnosed
Simple ranulas are often diagnosed on physical examination alone. The bluish, translucent swelling on the floor of the mouth is distinctive enough that additional testing isn’t always necessary. A doctor or dentist can typically identify one by its appearance and location.
Imaging becomes more important for plunging ranulas or when the diagnosis is uncertain. Ultrasound is the first-line imaging tool, useful for assessing the size and extent of the fluid collection. CT scans and MRI provide more detailed views when the ranula is large, recurrent, or extends deep into the neck. MRI is particularly helpful for ruling out other possibilities like vascular malformations. In some cases, a diagnostic puncture of the lesion is performed to confirm the contents are mucus.
Conditions That Look Similar
Several other conditions can mimic a ranula. Dermoid cysts, which are slow-growing developmental masses, can appear in the floor of the mouth but tend to feel firmer. Lymphatic malformations (lymphangiomas) can also present as soft, fluid-filled swellings in the same area. Salivary stones cause swelling too, but they usually produce pain, especially during meals when saliva production increases. A blocked or infected salivary gland can create swelling that overlaps with ranula symptoms. Because plunging ranulas present as neck masses, they can initially be confused with thyroglossal duct cysts, branchial cleft cysts, or even lymph node enlargement.
Treatment Options and Recurrence Rates
Treatment depends on the type and size of the ranula, and recurrence is the central challenge. Simpler approaches are less invasive but come back more often, while more definitive surgery has the best long-term success.
Incision and drainage (simply cutting the ranula open and letting the fluid out) is the least invasive option, but it has a recurrence rate around 70%. The pseudocyst wall and the underlying gland remain intact, so saliva simply accumulates again.
Marsupialization, where the ranula is opened and its edges are stitched to the surrounding tissue to create a permanent drainage pathway, sounds like a reasonable middle ground. In practice, it fails 53% to as high as 89% of the time. This has led most specialists to move away from it as a standalone treatment.
The most effective approach is removal of the sublingual gland itself, sometimes combined with excision of the pseudocyst. When the gland is removed through an intraoral approach along with drainage of the cyst, recurrence drops to essentially 0% in reviewed case series. This makes sense: eliminating the source of the leaking saliva prevents the problem from recurring. For plunging ranulas, removing the gland through the mouth while draining the neck component has a recurrence rate under 4%.
For patients who want to avoid surgery or who have medical reasons that make it risky, sclerotherapy is an alternative. This involves injecting a substance into the pseudocyst that causes it to shrink and scar down. In a study of 21 patients with plunging ranulas treated with sclerotherapy, about a third achieved complete resolution and another 19% saw more than 90% shrinkage. The final recurrence rate after the last injection was 14%, making it a reasonable option when surgery isn’t preferred.
Risks of Surgical Treatment
Because the sublingual gland sits close to important nerves, surgery carries some risk. The lingual nerve, which provides sensation and taste to the front two-thirds of the tongue, runs directly through the surgical area. Damage to this nerve can cause numbness, tingling, or altered sensation on the affected side of the tongue. While this complication is recognized and reported in the surgical literature, experienced surgeons take care to identify and protect the nerve during the procedure. The submandibular duct also passes nearby and needs to be preserved to maintain normal saliva drainage from the remaining glands.
Recovery from sublingual gland removal is generally straightforward. The surgery is performed through the mouth, so there are no external scars. Swelling and mild discomfort in the floor of the mouth are expected for several days. Losing one sublingual gland does not cause noticeable dry mouth, since the body has multiple salivary glands that compensate.