Ranula – Clinical presentation, diagnosis and management

Ranula is an uncommon clinical condition characterized by a translucent, blue cystic swelling in the floor of the mouth, arising due to accumulation of extravasated mucus from the sublingual salivary glands.

The term ranula arises from the Latin word rana, meaning frog as the condition resembles the underbelly of a frog. Hippocrates was the first to describe ranulas and he thought they were secondary to inflammation. Paré considered that ranulas may represent the descent of brain or pituitary matter, and W. Boyd described ranula as a dilatation of the duct of the submandibular gland.

The estimated prevalence of this condition is about 0.2 cases per 1,000 persons, but it is the most common pathologic lesion associated with the sublingual glands. A slight female predominance is mentioned in the literature. Ranula may be congenital or acquired and on rare occasions maybe even found in newborns. Ranula tends to present usually in the young age group, most often in the first, second, or third decade with a peak incidence in the second decade of life.

Types of ranula

• Sublingual / Intraoral type: This is the most common type which presents as an intraoral sublingual swelling.
• Plunging type: The second commonest is the “Plunging ranula” occurring when extravasation of mucus occurs beyond the confines of the floor of mouth through mylohyoid muscle into the upper neck or submental region.
• Mixed / Sublingual plunging type: These groups having both cervical and oral components.

Etiopathology

The exact etiology of this condition is unknown. It is considered that distal obstruction to sublingual salivary gland leads to increased tension inside the excretory ducts. This will lead to rupture of the acini which is followed by extravasation and salivary accumulation into the surrounding tissue. This extravasated mucous causes granulomatous reaction (mucus escape reaction/MER) leading to the formation of a pseudocyst that lacks epithelial lining.

Congenital ranulas may arise secondary to an imperforate salivary duct or ostial adhesion. These are quite rare and have been known to spontaneously resolve. Infantile ranula is thought to arise from developmental defects or birth trauma.

Less than 10% of ranulas are retention cyst (epithelial-lined) when the rupture of acinis won’t happen as in partial obstruction of sublingual duct.

Congenital dehiscence in the mylohyoid muscle has been suggested as an etiology for plunging ranula. Presence of an ectopic sublingual salivary gland is considered in case of plunging ranula without an oral component.

Clinical presentation of ranula

The characteristic feature of ranula is a smooth cystic swelling under the tongue, usually to one side. It is often transparent or bluish in appearance with overlying small blood vessels. In a deeper ranula, there will be a greater thickness of tissue separating the lesion from the oral cavity and the blue translucent appearance may not be a feature.

Usually, the condition is asymptomatic. But large swellings may push the tongue backward and affect speech, mastication, respiration, and swallowing due to the upward and medial displacement of the tongue.

Diagnosis and differentials

The diagnosis of ranula is mainly on a clinical basis. The diagnostic features of ranula are

• Mostly seen in young children and adolescents.
• Swelling in the floor of mouth, which may be painful.
• Mostly unilateral, on one side of frenulum.
• Spherical in shape with size varies from 1 – 5 cm in diameter
• Color is pale blue with characteristics semi-transparent appearance.
• The surface is smooth and the mucous membrane is mobile over the swelling.
• Tenderness is absent
• Fluctuation test is positive
• Transillumination test is positive
• Cervical lymph nodes are not enlarged.
• May or may not have extension into the neck.

The differential diagnosis for ranula are masses and swellings in the floor of the mouth and submandibular space region. These include, but not limited to, cystic hygroma, dermoid and epidermoid cysts, thyroglossal duct cysts, branchial cleft cysts, lipomas, abscess, and malignant neoplasia.

Investigations

Imaging studies are done in ranula mainly to know the extension of swelling prior to surgery or when the diagnosis is unclear. They include

• Ultrasonography (USG): Ultrasonography is usually inconclusive to study sublingual glands due to their location. Uncomplicated ranulas appear as a thin-walled cystic lesion, and can be imaged both from the skin or trans-orally with a small probe. If infected the walls are thicker and the fluid content more echogenic. In case of plunging ranula, USG can confirm the cystic nature of the lesion and the mylohyoid muscle integrity.
• Computed tomography (CT): On CT, the simple ranula is usually a roughly ovoid-shaped cyst with a homogeneous central attenuation region of 10 to 20 HU. A characteristic “tail sign” may be present in case of plunging ranula extending into the sublingual space.
• Magnetic resonance imaging (MRI): is the most sensitive imaging study to evaluate the sublingual gland and its pathologic states. On MR imaging, the ranula’s characteristic appearance is usually dominated by its high water content. Thus, it has a low T1-weighted, an intermediate proton density, and high T2-weighted signal intensity.

Sialochemistry of the ranula aspirate will reveal high amylase and protein contents consistent with secretions from the mucinous acini in the sublingual gland.

Histopathology: A ranula consists of a central cystic space containing mucin and a pseudocyst wall composed of loose, vascularized connective tissues with absent of epithelial tissues. Obtaining a specimen for pathological examination is essential squamous cell carcinoma arising in the cyst wall of a ranula and papillary cystadenocarcinoma of the sublingual gland presenting as a ranula have been reported in the literature.

Treatment of ranula

Many congenital ranulas resolve on their own and do not require surgical intervention. These children can be kept under observation until they are asymptomatic.

Various treatment modalities for ranula are described in the literature like simple aspiration, surgical excision via an intraoral or cervical approach, marsupialization or attempts at inducing fibrosis and scarring with varying recurrence rates.

• Simple aspiration or drainage of ranula: This results in a high recurrence rate (81-100%). Zhi et al recommend a graduated approach for the treatment of ranula in children, beginning with aspiration with marsupialization reserved for recurrences. If the ranula still recurs after these procedures, then excision of ipsilateral sublingual gland and ranula is recommended.
• Marsupialisation: Simple marsupialization is associated with recurrence rates ranging from 14% to 67%. Yuca et al. considers marsupialization as the suitable and effective primary method for treating pediatric oral ranulas. Ipsilateral sublingual gland excision can be combined in recurrent cases. Baurmash et al have shown that after marsupialization, firmly packing ranula cavity with gauze left in place for 7 to 10 days will provide better success rates.
• Ranula excision: Both simple and plunging ranula needs to be excised, together with cyst wall. Plunging ranula may need an external (cervical) approach for excision. The recurrence rate after ranula excision is reported to be 12-58%.
• Sublingual gland excision with ranula evacuation: This treatment modality is proposed by Zhao for both oral and plunging ranulas, was associated with a 1% risk of recurrence.
• Sublingual gland plus ranula excision: Many surgeons consider excision of the sublingual gland with ranula as the definitive treatment associated with the least risk of recurrence. The lingual nerve is at risk of injury during this procedure and care must be taken to identify and preserve the nerve during dissection.
• Submandibular and sublingual gland excision plus ranula excision: 23% of head and neck surgeons prefer to treat a plunging ranula with excision of the ranula along with the removal of the sublingual and submandibular gland. Transient tongue hypesthesia is reported as a complication of this method.
• CO2 Laser: The CO2 laser has been used with a limited number of patients with good success to remove the cyst and scar the gland enough to decrease the risk for recurrence.
• Radiation Therapy: In very few patients who cannot tolerate surgery, radiation therapy can be considered as a viable alternative. Low doses of 20–25 gray with shielding of the opposite side parotid gland is effective and won’t cause Xerostomia (dry mouth). The risk of radiation-induced malignancy is real but small.
• Sclerotherapy: There exists a few case reports with the injection of OK-432 sclerosant as a treatment to cause fibrosis and scarring of the lesion. The sclerosant used is a mixture of a low virulence strain of Streptococcus pyogenes incubated with benzylpenicillin. The therapy is associated with similar recurrence rate to surgical excision but without the risk of damage to the lingual nerve. Multiple injections may be needed depending on the size of ranula and concentration of the sclerosant for complete resolution.
• Oral administration of Nickel Gluconate-Mercurius Heel-Potentised Swine Organ Preparations D10/D30/D200: Garofalo et al have administered this homotoxicological agent orally for a minimum of 6 weeks and a maximum of 6 months in 18 children. The author believes that these drugs act synergistically on foreign body inflammation, triggered by extravasated mucus and stimulate pseudocyst reabsorption, glandular repairing and physiological function according to classical homeopathy principles.
• EXIT Procedures: In lesions diagnosed antenatally where the oral mass can be life-threatening, Kolker et al described the ex utero intrapartum treatment (the EXIT technique).

Patel et al from the University of North Carolina recommends that

• first-line treatment for oral ranulas is marsupialization, although the recurrence rate is higher.
• definitive treatment yielding the lowest recurrence and complication rates for both oral and plunging ranulas is the removal of the ipsilateral sublingual gland with the evacuation of the ranula.
• excising of ranulas is unnecessary because they are not true cysts.
• attempts to excise the ranula in conjunction with the sublingual gland likely places the lingual nerve and submandibular duct at even more risk due to more invasive dissection. 
• cervical approach for plunging ranulas is not warranted because ranula excision is unnecessary and the submandibular gland has no causal relationship to ranula formation. This even places marginal mandibular and hypoglossal nerves at unnecessary risk.

References

1. Kokong D, Iduh A, Chukwu I, Mugu J, Nuhu S, Augustine S. Ranula: current concept of pathophysiologic basis and surgical management options. World journal of surgery. 2017 Jun 1;41(6):1476-81.
2. Nguyen BN, Malone BN, Sidman JD, Roby BB. Excision of sublingual gland as treatment for ranulas in pediatric patients. International journal of pediatric otorhinolaryngology. 2017 Jun 1;97:154-6.
3. Patel MR, Deal AM, Shockley WW. Oral and plunging ranulas: What is the most effective treatment?. The Laryngoscope. 2009 Aug 1;119(8):1501-9.
4. Woo JS, Hwang SJ, Lee HM. Recurrent plunging ranula treated with OK-432. Eur Arch Otorhinolaryngol 2003;260:226-8.  Back to cited text no. 18Woo JS, Hwang SJ, Lee HM. Recurrent plunging ranula treated with OK-432. Eur Arch Otorhinolaryngol 2003;260:226-8.
5. Rho MH, Kim DW, Kwon JS, Lee SW, Sung YS, Song YK, et al. OK-432 sclerotherapy of plunging ranula in 21 patients: It can be a substitute for surgery. AJNR Am J Neuroradiol 2006;27:1090-5.
6. Garofalo S, Briganti V, Cavallaro S, Pepe E, Prete M, Suteu L, et al. Nickel Gluconate-Mercurius Heel-Potentised Swine Organ Preparations: A new therapeutical approach for the primary treatment of pediatric ranula and intraoral mucocele. Int J Pediatr Otorhinolaryngol 2007;71:247-55.