Mucocele and Ranula

Etiology

Mucoceles occur when there is an injury to the minor salivary glands, which are scattered throughout the oral cavity. The most frequent involved minor salivary glands are those of the lower lip, which can be injured in a variety of ways. Among them, mechanical trauma is the most common in biting one's own lip during chewing.[5] Other means by which these glands can be injured include chronic inflammation/irritation (e.g., from heat and smoking), excretory duct fibrosis, trauma from intubation, and rarely from sialolithiasis of the minor salivary glands.[6]

The origin of ranulas is similar to that of mucoceles with trauma to the excretory duct of the major salivary glands as the leading cause and obstruction of the duct (sialolith or mucus plug) as the less common one. Other causes leading to ranulas formation include chronic inflammation (sarcoidosis and  Sjogren syndrome) or infection (HIV) with periductal scarring, ductal hypoplasia, ductal stenosis, ductal agenesis, and neoplasia.[7] Anatomic variation in the ductal system of the sublingual gland may increase the risk of development of a ranula. The risk appears to be increased when the Bartholin duct is connected to and empties into the Wharton duct.[8]

Epidemiology

The prevalence rate of mucoceles is 2.4 cases per 1000 persons, with the highest percentage (70%) occurring in those ranging from 3-20 years old.

Ranulas, on the other hand, have a frequency of 0.2 cases per 1000 persons. Like mucoceles, these lesions also have a predilection for teenagers and young adults.[4]

The inner aspect of the lower lip, often subjected to trauma such as lip biting, is a common site for the development of mucoceles. However, they can develop anywhere in the oral cavity. Other common sites for mucoceles development involve the soft palate, retromolar region, and the dorsum of the tongue. For ranulas, the floor of the mouth is the most common site to develop. Although sublingual glands give rise to most of the ranulas (90%), they may arise from the submandibular gland in rare cases.

No racial or sexual predilection has been reported for these lesions.

Pathophysiology

The primary pathology that lies behind the formation of mucoceles and ranulas is the disruption to the flow of secretions of salivary glands. Trauma is the most common cause, following which mucus extravasates and accumulates in the surrounding tissue. Another way that leads to the development of these lesions is the obstruction of the excretory duct of the salivary glands secondary to sialolith, periductal scarring or fibrosis, tumor.

History and Physical

Patients with mucoceles present with asymptomatic, painless swelling in their mouths.[9] These lesions develop suddenly and enlarge rapidly and become fluctuant. Many tend to involute spontaneously as the mucocele ruptures, and its content gets reabsorbed by the oral mucosa.[10][11] There may be a trauma to the face or mouth either in the form of oral surgery or tongue biting, but mostly no traumatic cause is identified. The course of these lesions ranges from 3 to 6 weeks, with some taking a few days to years to resolve in rare cases.

Patients with oral ranula mostly present with painless swelling in the floor of the mouth. This swelling can interfere with speech, swallowing, mastication, and even respiration as it displaces the tongue in an upward and medial direction. Sometimes, the tongue may put pressure on the lesion, interfering with the saliva outflow, thus leading to obstructive salivary gland signs and symptoms (pain when eating or chewing).

Cervical ranula, however, presents as an asymptomatic mass in the neck. There is usually a trauma to the floor of the mouth or dental surgical procedure leading to the lesion.

On physical examination, mucoceles appear as dome-shaped, non-tender, fluctuant, non-blanchable on applying pressure, and mobile swellings ranging from 0.1-4 cm in size. While superficial mucoceles have bluish to translucent hue, deep lesions have pinkish mucosal color.[12] Although mucoceles can form anywhere in the oral cavity, about 80% tend to form in lower labial mucosa with the floor of the mouth, ventral tongue, buccal mucosa, and palate as less common sites.

Oral ranulas, on the other hand, appear as large, cystic, translucent to blue swelling in the floor of the mouth resembling the belly of a frog.[13] Like mucoceles, they have a soft consistency and do not blanch on compression. Cervical ranulas or plunging ranulas present as an asymptomatic, mobile, fluctuant, and enlarging mass in the neck, having soft consistency. Like oral ranulas, they mostly occur unilaterally but may cross the midline.

Evaluation

The diagnosis of mucocele and oral ranula is mainly based on the clinical picture. Although imaging studies are not generally indicated for the evaluation of mucoceles and oral ranulas, they can undoubtedly help in excluding other differential diagnoses, determining the cause (e.g., calculi) as well as the extent of the swellings, thus aiding in surgery.[5]

• Ultrasonography: In expert hands, high-resolution ultrasonography can detect calculi, abscesses, and cysts, and can even correctly assess up to 90% of benign versus malignant tumors. Vascular lesions, however, require color doppler imaging for their evaluation.
• CT and MRI: They are seldomly required, except if there is a large plunging or cervical ranula that has breached through a defect in the mylohyoid muscle. Also, they aid in determining the extent of the swelling, which is crucial to know before proceeding to the surgery.[1]
• Biopsy: It is required to differentiate between the benign and the malignant disease.

Treatment / Management

Mucoceles and ranulas tend to resolve spontaneously. But if they are symptomatic, persistent, and are not self-resolving, multiple treatment approaches can be considered, which are discussed below.

• Mucoceles                1. Surgical Excision: Surgical excision of the mucocele along with the associated minor salivary gland, is preferred when the lesion is persistent, recurrent, or symptomatic. After adequate removal, the chances of recurrence are reasonably low.2. Aspiration: It is not considered as an appropriate therapy for mucoceles as the recurrence rate is quite higher. Instead, it is preferred to eliminate other entities before surgical excision.3. Marsupialization: It is performed when the lesion is more extensive as it prevents the significant loss of the tissue and also decreases the risk of complications occurring as a result of surgical excision. However, if it fails, then surgical removal of the lesion is performed. Micromarsupialization of lesions smaller than 1 cm in diameter has been reported in pediatric patients with variable success in which a suture is taken through the dome of the lesion, allowing re-epithelialization of the injured duct and improving the secretory flow of the minor salivary gland.[14]4. Laser Ablation, Cryosurgery, and Electrocautery: They are mostly performed for the superficial mucoceles.[1][15]
(A1)

• Ranulas1. Surgical Excision: Both oral and cervical ranulas can be treated effectively with this approach involving the removal of the lesion along with the associated major salivary gland with insignificant recurrence rates.2. Marsupialization: Some providers prefer it before embarking on surgical removal. The whole pseudocyst is packed with gauze for 7-10 days. This allows re-epithelialization of the cavity and also seals off the leakage site. Besides, it also provokes a foreign body reaction causing fibrosis and atrophy of the offending acini. If marsupialization fails to eliminate the disease, then surgical excision is the next treatment of choice. 3. Laser Ablation, Cryosurgery, and Electrocautery: These have also been employed for the treatment of smaller ranulas either alone or before the marsupialization.4. Intralesional Injection of a Sclerosant Agent: Although considered experimental, intracystic injection of the streptococcal preparation, OK-432, has been reported to treat the disease with variable success rates.[16][17]
(B2)

Differential Diagnosis

Mucoceles and ranulas occurring beneath the tongue may mimic a lot of other entities and must be differentiated. The broad list of differential diagnosis of these lesions is as follows.

• Hemangioma
• Lymphangioma
• Dermoid cyst
• Benign or malignant salivary gland neoplasm
• Lipoma
• Abscess
• Venous lake
• Fibroma
• Benign mesenchymal neoplasm

Prognosis

Overall the prognosis for mucoceles and ranulas is quite good. Mostly, these lesions present as painless and asymptomatic swellings in the oral cavity with no associated morbidity or mortality. However, some large lesions may interfere with the speech, mastication, deglutition, or even with the respiration depending on the location. With complete excision of the lesion along with the offending gland, the recurrence rate is significantly low. In contrast, other procedures, including marsupialization and aspiration of the cyst, are associated with a higher recurrence rate. In recent pediatric studies, the recurrence rates range from 6%-8% following surgery.[18][19]

Complications

Complications of mucoceles and ranulas include:

1. Infection
2. Rupture and reformation
3. Dysphagia in case of large ranula

Possible surgical complications include the following:

Intraoperative

1. Hemorrhage
2. Wharton duct damage leading to stenosis, and obstructive sialadenitis
3. Injury to the lingual nerve causing temporary or permanent paresthesia
4. Facial nerve marginal mandibular branch damage-causing paresthesia

Postoperative

1. Hematoma
2. Infection
3. Dehiscence of the wound

About half of the plunging or cervical ranulas arise as a result of the failure to excise oral ranulas completely. These plunging ranulas may enlarge and result in a respiratory compromise or acute mediastinitis, a life-threatening complication.