Ranula excision

Salivary gland abnormalities can manifest as intraoral or cervical masses or both. A ranula is a cystic lesion that arises from the sublingual gland and is among the most common intraoral salivary gland masses. The term ranula is derived from the Latin word rana, meaning frog. Reminiscent of a frog’s underbelly, a ranula classically appears as a translucent swelling in the floor of the mouth.

The sublingual gland is the smallest and the only unencapsulated major salivary gland. As a paired almond-shaped structure, each gland is bound by the floor of the mouth mucosa superiorly, mylohyoid muscle inferiorly, mandible laterally, genioglossus muscle medially, and submandibular gland posteriorly. There are no posterior fascial limits to the sublingual glands; thus, lesions that arise from the gland can exit and spread to the submandibular and the parapharyngeal spaces.

Each gland is drained by 5-15 minor excretory ducts (Rivinus ducts) that carry saliva into the oral cavity through small mucosal folds in the floor of the mouth (plica sublingualis). At times, the ducts can coalesce into a larger duct (Bartholin duct) that drains directly into the submandibular duct and out through the sublingual caruncle. Branches of the lingual and the facial arteries supply the sublingual glands. The sublingual glands produce a constant flow of saliva that is highly proteinaceous in consistency, and they yield 10% of the oral cavity’s total saliva output.

A ranula can either be simple or plunging based on the location of the cyst relative to the mylohyoid muscle, with a simple ranula being confined above the mylohyoid and a plunging ranula extending inferior to the muscle. Plunging ranulas are thought to arise secondary to either (1) congenital dehiscence of the mylohyoid muscle that allows herniation of a part of the sublingual gland or the pseudocyst sac into the submandibular space or (2) posterior extension between the mylohyoid and the hyoglossus muscles where there is no fascial boundary.

A ranula is the result of sublingual duct obstruction or disruption. Intraoral ranulas are usually the result of salivary duct obstruction with resultant formation of a mucous retention cyst. Plunging ranulas are typically caused by a collection of mucus that extravasates into adjacent tissue, inducing an inflammatory response that walls off the mucus collection. Thus, as a pseudocyst, it lacks a true epithelial lining. Mucus is thought to collect and escape secondary to sublingual duct obstruction, duct injury, or ruptured acini, which in turn develops because of mucosal inflammation, immunologic abnormalities, sialolith, congenital abnormalities, direct trauma, and rarely, tumor.

Histopathologic examination of a plunging ranula demonstrates a mucin-containing pseudocyst surrounded by a wall made up of vascularized fibroconnective tissue, resembling granulation tissue with a predominance of histiocytes (macrophages). There is an absence of epithelial tissue in the wall. Biopsy of the cystic wall at the time of sublingual gland excision is recommended to confirm the diagnosis.

Ranulas occur most commonly in the second and third decades of life, though there are reports of cases across age groups ranging from 3-61 years. There is a slight female to male predominance of 1.3:1. Classically, simple ranulas present as fluctuant swellings in the floor of the mouth that cause discomfort or speech difficulty. The size or position is unaffected by chewing, eating, or swallowing. Plunging ranulas present as fluctuant cystic neck masses, most commonly in the submandibular space, though they have been described in the ipsilateral or the bilateral parapharyngeal and retropharyngeal spaces and even in the lower neck and the mediastinum. Plunging ranulas can present without an obvious intraoral component in at least 20% of cases. Risk factors for ranula development include prior salivary gland infection, trauma, or surgery in the submandibular space.

Indications for surgical excision include airway compromise, rarely present, or speech and swallowing complaints, recurrent infection, or secondary impaired function of the submandibular gland. Active infection and comorbidities that increase general anesthesia risks are relative contraindications to elective excision.

A complete history and physical examination is the cornerstone of the evaluation of intraoral and cervical masses. Ranulas can be evaluated by inspection and palpation of the floor of the mouth for a fluctuant swelling, often with a bluish hue.

Imaging can be used as an adjunct in diagnosis and surgical planning. Computed tomography and magnetic resonance imaging (MRI) with contrast agent can help distinguish ranulas from other lesions of the floor of the mouth. The differential diagnosis for an intraoral ranula includes foregut duplication cysts, lymphatic malformations, and dermoids. The differential diagnosis of a plunging ranula is broader and includes thyroglossal duct cyst, branchial cleft cyst, epidermoid cyst, laryngocele and lymphatic or vascular malformations, and solid neck masses such as lipomas, dermoids, submandibular gland neoplasms, and lymphadenopathy. On MRI, ranulas appear bright with well-defined borders on T2-weighted images. Imaging can also be used to delineate the relationship of the ranula to adjacent structures, particularly in the case of plunging ranulas.

Various surgical and medical options have been reported for the treatment of ranulas, including OK-432 (or bleomycin) sclerotherapy, incision and drainage, marsupialization, and cyst excision with or without sublingual gland removal via intraoral, transcervical, or dual approaches. Recurrence rates are variable but are in excess of 50% for any surgery in which the sublingual gland is not excised. The recurrence rate can be as high as 70% with incision and drainage of the cyst alone and 53% with marsupialization, during which the cyst is deroofed with cautery or laser and the cavity is kept open for drainage by suturing the cut edges together. Irrespective of complete cyst wall excision, excision of the sublingual gland yields a recurrence rate of less than 2%. Sclerotherapy, with the streptococcal preparation OK-432, has emerged as a possible nonsurgical option, but it induces fever and pain in half of patients and may require repeat injections.

Simple oral ranulas are excised through an intraoral approach. Plunging ranulas can be excised through an intraoral or a cervical approach. Excision of the ipsilateral sublingual gland is important through either approach to prevent recurrence. Complete excision of the pseudocyst wall is not necessary, as it represents an inflammatory response to the extravasated mucus and should resorb once the inciting mucus is removed. Moreover, care should be taken with extensive dissection, which can risk unnecessary injury to the nearby lingual nerve and the submandibular duct.

The patient is positioned supine on the operating table. Administration of general anesthesia via a nasotracheal tube is recommended. If endotracheal intubation is performed, the tube should be taped to the contralateral side. An intraoperative dose of intravenous antibiotics can be given.

A Jennings mouth gag or dental bite block is placed to allow visualization. A 2-0 silk suture through the tongue tip allows for gentle tongue retraction (Figure 1). Alternatively, a sweetheart retractor can be used. A lacrimal probe cannulates the submandibular duct to prevent inadvertent injury and to aid with duct identification. Local anesthesia using 0.5% lidocaine with 1:200,000 epinephrine is injected into the mucosa overlying the sublingual gland.

An elliptical incision is made through the floor of the mouth mucosa overlying the ranula using monopolar cautery with a needle tip or #15 blade scalpel (Figure 2). The floor of the mouth mucosa is left in continuity over the ranula to aid with retraction and prevent disruption of the wall. Sutures or Ragnell retractors are placed on each side of the mucosal flaps to aid in retraction. Using blunt dissection, the medial boundary of the cyst is delineated (Figure 3). Careful dissection is necessary in this area to avoid injury to the nearby lingual nerve and the submandibular duct. The lingual nerve enters the floor of the mouth between the hyoglossus muscle and deep lobe of the submandibular gland and then travels from lateral to medial toward the tip of the tongue. During its route toward the tongue tip, the lingual nerve passes inferior to the submandibular duct, which is an important relationship to remember. Once the medial border of the ranula is freed, dissection proceeds laterally toward the sublingual gland of origin. The ranula is bluntly dissected off the underlying mylohyoid muscle. Depending on the size of the cyst, the cyst can be excised completely along with the sublingual gland, or its contents can be evacuated in cases of large ranulas in which excision can risk injury to adjacent structures. The vascular pedicle to the sublingual gland is located medially and posteriorly and is the last one to be ligated.

Once the cyst and the sublingual gland are delivered, the wound is irrigated copiously and closed loosely using interrupted 4-0 VICRYL or chromic sutures (Figure 4).

A cervical incision can be performed for plunging ranulas in which the cyst cannot be accessed intraorally or in the case of a large cyst. This is done via a similar approach as a submandibular gland excision to access the submandibular space. For the external approach, it is important to avoid using paralytic agents so that monitoring of the marginal mandibular branch of the facial nerve and the hypoglossal nerve can be performed.

An incision using a #15 blade scalpel is made through the skin, subcutaneous tissue, and platysma, at least 2 fingerbreadths below the angle of the mandible, to decrease the risk of injury to the marginal mandibular branch of the facial nerve (Figure 5). Subplatysmal flaps are elevated, and the fascia overlying the submandibular gland (superficial layer of the deep cervical fascia) is exposed (Figure 6). Dissection is carried onto the submandibular gland and the facial vein is identified, cross-clamped, and divided. The facial vein and the submandibular fascia are dissected off the submandibular gland, thereby protecting the marginal mandibular branch of the facial nerve (Figure 7). The facial artery is also identified over the posterior border of the gland and is ligated. The submandibular gland is dissected free from the ranula and retracted anteriorly or resected, depending on access to the ranula. The hypoglossal nerve is identified deep to the submandibular gland and is carefully preserved. The mylohyoid muscle is then retracted anteromedially, and the lingual nerve is identified and preserved. The cervical component of the ranula is then bluntly dissected off the underlying hyoglossus and genioglossus muscles. The ranula tract often parallels the submandibular duct, which is traced superiorly through the mylohyoid. Using intraoral palpation, the sublingual gland is displaced inferiorly into the neck and resected in continuity through the cervical approach. The wound is copiously irrigated and a Penrose drain is placed in the cavity, exiting from the side of the incision, to be removed on postoperative day 1 or 2, depending on output (Figure 8). The wound is closed in layers using 4-0 VICRYL sutures to reapproximate the platysma and deep dermal layers. The skin is closed with 5-0 PROLENE or fast gut sutures.

An intraoperative dose of intravenous antibiotics is standard at our institution. Additional postoperative antibiotics are optional. With a transoral approach, postoperative oral hygiene is recommended with routine mouth rinses after meals. The patient can resume a regular diet.

Complications associated with sublingual gland excision include postoperative edema, hematoma, infection, recurrence, and injury to adjacent structures, notably to the lingual nerve and the submandibular duct. Recurrent ranulas can form particularly if the sublingual gland is not excised. Injury to adjacent structures include trauma to the submandibular duct, which can become stenotic or leak, resulting in sialoadenitis. Injury to the lingual nerve results in ipsilateral tongue paresthesia, which is often transient, lasting up to 6 months, but can be permanent.

Ranulas are mucin-containing pseudocystic lesions that develop in the floor of the mouth, in the neck, or both because of obstructed flow or injury to the sublingual gland ducts or acini. They manifest as painless, fluctuant masses in these areas. Workup relies on a complete history and physical examination to distinguish these lesions from other cystic abnormalities. Computed tomography or MRI with contrast agent can be useful adjuncts for diagnosis. Surgical excision remains the mainstay for management. The most important factor influencing the success of surgical management is removal of the responsible sublingual gland.