Sublingual Caruncle: Anatomy, Salivary Ducts, and Stones

The sublingual caruncle is a small, raised mound of tissue on the floor of the mouth, one on each side of the frenulum (the thin fold of tissue under your tongue). Each caruncle serves as the exit point where saliva from the submandibular gland, and sometimes from the sublingual gland, flows into the mouth. Despite being only a few millimeters across, this structure sits at a surprisingly busy anatomical crossroads, and when something goes wrong with it, the consequences range from minor discomfort to significant swelling that can interfere with eating and speaking.

Where Exactly It Sits and What It Looks Like

If you lift your tongue and look in a mirror, the sublingual caruncle appears as a small, fleshy bump on either side of the lingual frenulum, right where the floor of the mouth meets the base of the tongue. It is pinkish or slightly redder than the surrounding tissue and often has a visible dimple or opening at its peak. That opening is the ostium of Wharton’s duct, the main drainage channel of the submandibular salivary gland. In some people, a second, smaller opening sits very close by, belonging to the Bartholin duct of the sublingual gland.

You can sometimes see saliva pooling or even spurting from the caruncle when you eat something sour or press gently beneath your jaw. The submandibular glands produce a large share of resting saliva, so most of the fluid that keeps your mouth moist between meals enters through these tiny paired mounds. The tissue itself is covered by oral mucosa and sits directly over a dense network of blood vessels and minor salivary tissue in the floor of the mouth.

The Ductal System That Drains Through It

One of the reasons the caruncle matters clinically is that it sits at the terminus of a ductal system with a surprising amount of anatomical variation. The submandibular gland’s Wharton duct is the primary channel, running forward from the gland along the floor of the mouth and exiting at the caruncle’s ostium. The sublingual gland, which sits closer to the front of the mouth, has a more complicated arrangement.

A detailed anatomical study that dissected sublingual gland specimens found four distinct drainage patterns:

Parallel but separate: The sublingual gland sends one Bartholin duct that runs alongside Wharton’s duct and opens at its own small orifice near, but not connected to, the Wharton duct opening. This was the most common pattern, found in about 36% of specimens.
Joining Wharton’s duct: The Bartholin duct empties into the midsection of Wharton’s duct, so both glands share a single exit point at the caruncle. This occurred in about 32% of cases.
Dual Bartholin ducts: The sublingual gland sends two separate ducts, one joining Wharton’s duct and the other opening independently nearby. This was rare, at about 7%.
Rivinus ducts only: The sublingual gland has no Bartholin duct at all and instead drains through many fine ducts (called Rivinus ducts) that open along the sublingual fold rather than at the caruncle. This pattern appeared in 25% of specimens.

The practical upshot is that in roughly 39% of people, the sublingual and submandibular ducts directly communicate with each other before reaching the caruncle.¹ This interconnection matters because disease in one gland can produce symptoms that appear to come from the other. A blocked sublingual duct, for example, can cause saliva to back up through a shared channel and swell the submandibular gland instead.

Histological examination in animal models has confirmed that both the major sublingual duct and the submandibular duct travel within the tissue of the sublingual caruncle itself, with the sublingual duct lining containing more mucus-producing goblet cells than the submandibular duct lining.² That difference in cell type reflects the fact that the sublingual gland produces thicker, more mucus-rich saliva, while the submandibular gland produces a thinner, more watery mixture.

Salivary Stones and the Caruncle

The most common problem people experience at the sublingual caruncle is obstruction by a salivary stone, known as a sialolith. These are calcified deposits that form inside the duct, and they have a strong preference for Wharton’s duct. The reason is partly mechanical: Wharton’s duct is long, it takes a winding upward path from the gland to the caruncle, and the saliva it carries is rich in calcium. All of those factors give minerals more opportunity to crystallize.

When a stone lodges near or at the caruncle, the classic presentation is sudden swelling beneath the jaw that worsens during meals, when saliva production spikes and has nowhere to go. The caruncle itself may look visibly swollen, red, and tender, and sometimes the stone is large enough to be felt or even seen as a hard lump at the duct opening. One published case described a 37-year-old woman whose sublingual caruncle was visibly bulging because a calculus had lodged right at the duct’s ostium, blocking saliva outflow and causing edema in the submandibular area.³

Stones that sit very close to the caruncle are actually the easiest to manage, because a clinician can sometimes push or milk them out through the duct opening with gentle pressure, or make a small incision in the floor of the mouth to extract them. Stones deeper in the duct require more involved approaches, including sialendoscopy (a tiny camera threaded into the duct) or, in stubborn cases, gland removal.

Stenosis at the Duct Opening

Not all obstructions at the caruncle are caused by stones. The duct opening itself can narrow, a condition called papillary stenosis. A study that classified stenoses found using sialendoscopy reported that nearly 59% of all submandibular duct stenoses were located right at the papilla, the caruncle’s duct opening. Most of these were short and high-grade, meaning significant narrowing over a short stretch of duct.⁴ The study distinguished inflammatory stenoses from fibrotic ones and from a third category caused by anatomical duct variations rather than disease. Inflammatory narrowing tended to be bilateral, affecting both sides, and shorter, while fibrotic stenosis was more often one-sided and longer.

The symptoms of papillary stenosis mimic those of a stone: meal-related swelling, discomfort under the jaw, and sometimes a discharge of thick or foul-tasting saliva when pressure is applied. The difference is that imaging may show no stone at all, which can be confusing for both the patient and the clinician until sialendoscopy reveals the narrowed opening.

When Dental Work Causes Trouble

One cause of papillary stenosis that often goes unrecognized is chronic irritation from dental prostheses. Because the sublingual caruncle sits on the floor of the mouth very close to the lower gum line, dentures and implant-supported prosthetics can press against or repeatedly rub the duct opening.

A retrospective study of nine patients with papillary stenosis found that in every case, sialendoscopy ruled out stones and inflammatory disease, leaving the mandibular dental prosthesis as the only identifiable cause. The stenosis was severe enough that the endoscope could not initially be inserted at all.⁵ A separate analysis of a larger database of 352 patients with submandibular gland obstruction identified three patients in whom implant-retained lower dentures appeared to be responsible. In all three cases, the sublingual caruncle was in close physical contact with the implant hardware or the bar connecting implants.⁶

If you have lower dental implants or a removable denture and experience recurrent swelling beneath the jaw during meals, it is worth asking your dentist or oral surgeon whether the prosthesis might be impinging on the caruncle. Adjusting the prosthesis to relieve pressure on the floor of the mouth can resolve the problem without any procedure on the duct itself.

Inflammation Beyond Stones and Mechanical Causes

Chronic inflammatory conditions can also affect the duct system at the caruncle. One unusual example is eosinophilic sialodochitis, a rare allergy-associated disease in which eosinophils (a type of white blood cell involved in allergic reactions) infiltrate the lining of the salivary duct, causing recurrent swelling and thick mucus discharge. A reported case involved a 58-year-old woman who experienced two years of recurrent submandibular gland swelling and throat itching before the condition progressed to chronic obstructive sialadenitis with actual stone formation.⁷ Cases like this show that prolonged ductal inflammation near the caruncle can itself set the stage for stones to develop later, creating a cycle of obstruction.

Congenital Problems With the Caruncle

Occasionally, the duct opening at the caruncle never forms properly. Infants or young children may be born with an imperforate sublingual caruncle, meaning the duct is present beneath the surface but has no exit through the mucosa. Saliva accumulates and forms a cyst on the floor of the mouth, which can interfere with feeding and sometimes with breathing if large enough. A systematic review of this condition found that a relatively simple procedure, excising the membrane covering the blocked caruncle (a sialodochostomy), with decompression of the cyst, was effective treatment.⁸ The procedure creates a new opening through which the duct can drain normally. Because the underlying gland and duct are structurally sound, outcomes tend to be good once the obstruction is relieved.

How Imaging Helps Identify Caruncle Problems

When a clinician suspects a stone, stricture, or other abnormality at the caruncle, the two main imaging options are ultrasound and sialography (injecting contrast material into the duct and then imaging it). A comparative study of 157 patients found that three-dimensional cone beam CT sialography detected ductal lesions in 113 patients, compared with 86 detected by ultrasound alone, giving the CT method higher sensitivity (0.85 versus 0.65). For stones specifically, both methods performed reasonably well, but CT sialography still held an edge in sensitivity (0.80 versus 0.75) and negative predictive value (0.88 versus 0.78).⁹

In practice, ultrasound is usually the first step because it is quick, painless, and widely available. If results are inconclusive, CT sialography or direct sialendoscopy (threading a miniature camera into the duct via the caruncle) can provide a clearer picture. Sialendoscopy has the added advantage of being both diagnostic and therapeutic: a stone or stricture found during the procedure can sometimes be treated in the same session.

The Caruncle as an Immune Monitoring Site

The sublingual caruncle is not just a passive drain for saliva. The saliva that exits here carries immune molecules, particularly secretory IgA antibodies, that reflect what is happening deeper in the body’s mucosal immune system. Researchers investigating whether saliva could serve as a stand-in for intestinal immune responses found a strong correlation between IgA antibody levels in sublingual and submandibular secretions and those in intestinal samples. About 93% of study participants showed a more than twofold increase in IgA antibodies against a challenge bacterium in their sublingual/submandibular saliva, compared with only 67% who showed a comparable response in parotid saliva. Using intestinal secretion as the reference standard, the sublingual/submandibular saliva had a sensitivity of 96% for detecting an immune response.¹⁰

This has implications for vaccine research and monitoring. If saliva collected from the caruncle area can reliably mirror gut immune responses, it could offer a painless, noninvasive alternative to intestinal biopsies or blood draws when evaluating mucosal vaccines. The research is still evolving, but it positions the sublingual caruncle as a surprisingly useful clinical window into mucosal immunity.

The History Behind the Names

The anatomical names associated with the caruncle carry centuries of backstory. Wharton’s duct is named after Thomas Wharton, the English physician who described the submandibular duct in the 1650s. Bartholin’s duct, the main duct of the sublingual gland, is named after Caspar Bartholin the Younger, a Danish anatomist working a few decades later. A historical review of these discoveries noted that religious, political, and philosophical factors of the Renaissance era shaped how these structures were understood and named, sometimes with competing claims of priority between anatomists in different countries.¹¹ The word “caruncle” itself comes from the Latin caruncula, a diminutive of caro (flesh), meaning a small fleshy prominence. The same root gives its name to other small fleshy structures in the body, such as the lacrimal caruncle at the inner corner of the eye.

The naming convention has stuck, and modern anatomy texts still refer to the sublingual caruncle as the standard landmark for identifying the submandibular duct’s exit. For dentists and oral surgeons, the caruncle is one of the first structures checked during a routine oral examination, and tenderness or swelling there immediately raises suspicion for salivary gland disease.