Introduction

Most patients presenting with obstructive symptoms of the submandibular gland (SMG) are afflicted with salivary stones rather than stenosis, and salivary gland stones are a more frequent cause of SMG obstruction than of parotid obstruction, in a ratio of 4 : 1. Traditionally, most stones in the proximal SMG and duct were treated with gland excision. Sialendoscopy has allowed for preservation of many of these glands. Functional radiologic studies have shown that these glands are functional after removal of salivary stones, even if they are of longstanding.

Presentation

Patients with stones of the SMG will generally have had the stones present for years. The consensus is that most stones grow at about 1 mm per year and our own experience with several patients, who elected not to have extraction, bears this out. Stones become symptomatic when they either block the free flow of saliva (obstructive, meal-time symptoms) or when they get infected. Both of these will present with unilateral SMG swelling and discomfort. Infected stones often develop a biofilm. While the development of infection with stones is relatively low, once it develops it can be hard to eradicate. On rare occasions, infection related to sialolithiasis can progress to abscess. Obstructive symptoms, on the other hand, may flare and abate over a period of years.

The medical history should include asking about diabetes, dehydration, and xerostomia/xerophthalmia associated with Sjögren syndrome, as all are associated with stone formation. Sjögren patients may have intraglandular calcifications on imaging and most of these are not intraductal stones, but they may also have obstructive symptoms from intraductal stones as well. A history of radiation is important because of the secondary salivary effects of either radioactive iodine or external beam radiotherapy, even though neither is associated with stone formation. Surgical history should include any prior salivary gland surgery.

Physical Exam

The exam should include a complete head and neck exam. The SMG papilla should be analyzed carefully. The SMG papilla can be the rate-limiting step in dilating the system for placement of the salivary endoscope. The authors therefore examine the papilla with the operating microscope in the office. In so doing, a notation in the chart is made of the exact location of the opening of the papilla while the patient is awake, hydrated, and salivating. If no saliva is present, the patient can be given a salivary stimulant; a hard candy will suffice. The opening is then described in the electronic record to facilitate intubation in the future. The ease of visualization of the papilla opening of the awake patient is one of the reasons that some practitioners perform the procedure under a local anesthetic, in the office. The entire duct should be palpated after visualization and the gland should be examined with bimanual palpation to feel for stones as well as neoplasms, which will occasionally present with a longer history mimicking an inflammatory etiology. The gland should be examined carefully and compared with the contralateral gland.

Patients with salivary gland pathology will often have abnormal characteristics of their saliva when viewed with the microscope. Patients with infection will have a very thick, purulent saliva; those with stones without infection will often have debris, and those with Sjögren and sialadenitis from I-131 will have very little saliva, and it is very thick.

Size, shape, orientation, and location of stones should be noted, as these factors determine options for retrieval. The normal width of the adult submandibular duct is 4 mm. Stones in the submandibular duct that are <4 mm in their maximum dimension are typically retrievable with a wire basket through an endoscope ( Fig. 17.1 ). Stones larger than this may still be retrievable with a basket if they meet the following criteria: the orientation of the long axis of the stone is along that of the duct; the shape of the stone is oval and smooth; and the diameter of the stone in the plane perpendicular to the duct is not >4 mm. In our series, the authors successfully retrieved SMG stones up to 9 mm in length along the duct, and oval-shaped stones up to 5.5 mm in width. Larger stones that were removed successfully with a wire basket were typically free floating upon irrigation of the duct (Video 17.1 ).

CT demonstrates a large stone removed with a wire basket. This patient’s CT demonstrates a right parotid stone that measured 0.9 mm along the duct and 0.3 mm wide and was successfully retrieved using a wire basket. Oval shape oriented along the length of the duct, free-flowing movement with irrigation, and a width no <4 mm were predictors for success.

The location of the stone also influences the surgical approach. Palpable anterior floor of mouth stones or stones at the papilla may be removed transorally in the office without the need for endoscopy. Stones located elsewhere along the duct or that are not palpable are better served with endoscopic localization and retrieval using endoscopic or combined techniques.

Indications for Surgery

Sialendoscopy should be offered in all patients with submandibular sialolithiasis who have obstructive symptoms and/or recurrent acute sialadenitis with or without abscess formation. Recurrent unexplained swelling of the SMG associated with meals is another indication. Asymptomatic patients with incidental sialoliths are offered endoscopy versus observation and counseled on the pros and cons of each. The pros of observation is the avoidance of surgical and anesthetic complications, and the cons include the future possibility of developing sialadenitis, neck abscess, and loss of the ability to retrieve the stone endoscopically as stone size increases over time. The only relative contraindication to interventional sialendoscopy is active sialadenitis due to an increased risk of ductal injury.

Surgical Planning

Obtaining informed consent for both sialendoscopy and a possible combination with an open approach is advised when endoscopic removal of a stone is anticipated to be challenging or not likely feasible. A combined procedure starts with endoscopic visualization and location of the stone followed by a standard external or intraoral approach to remove the stone, avoiding removal of the involved gland (see Chapter 18 ). Duct repair with stenting or marsupialization then follows (see Chapter 25 ). Stone fragmentation using a laser (see Chapter 22 ), stone fragmentation using pneumatic lithotripsy (see Chapter 23 ), and extracorporeal lithotripsy (see Chapter 24 ) are other approaches that can be considered for stones not amenable to endoscopic wire basket retrieval alone.

Sialendoscopy can be performed in the office setting or the operating room. In the authors’ practice, it is performed in the operating room, either under general anesthesia or with a combination of local anesthetic and sedation. When there is a known sialolith, general anesthesia is chosen, unless there is a patient comorbidity that precludes it.

Preoperative discussion with the anesthesia team should occur regarding the patient’s positioning, placement, fixation, route of insertion of the endotracheal tube, and absolute avoidance of anticholinergic/anti-sialagogue medication such as glycopyrrolate. The authors use oral intubation with the tube fixed to the opposite oral commissure for most patients undergoing endoscopy for SMG stones and find it provides adequate exposure to the anterior and posterior floor of the mouth. Nasal intubation offers a wider exposure of the oral cavity, but there is a risk of epistaxis, and is traditionally reserved for bilateral cases or for patients with a challenging access to the oral cavity (obese patients, large tongue, small mouth opening, tori, or large teeth). In patients with challenging oral access, typically two assistants are required, as external pressure on the SMG gland compressing it towards the floor of the mouth throughout the case is vital for success. Muscle relaxation is typically used for cases performed under general anesthesia for optimal intraoral access. A single intravenous dose of perioperative antibiotic to cover the oral flora is administered. The patient is positioned supine and the bed is rotated about 100 degrees, with a set-up similar to that of routine endoscopic sinus surgery. The right arm is tucked and the left armrest is positioned next to the bed to facilitate the surgeon and the assistant on opposite sides of the patient. Intraoral and extraoral Betadine prep is not felt to be necessary. The patient is draped with the neck and mouth exposed.