Introduction

Sialendoscopy involves the use of miniature endoscopes that are introduced into the main salivary ducts of the parotid or submandibular glands. Salivary duct endoscopy was first described in 1990 by Katz [1]. The equipment for sialendoscopy has continued to be modified and improved, enhancing minimally invasive approaches to the salivary duct [2]. Sialendoscopy can be performed for both diagnostic and therapeutic purposes including to evaluate the main salivary ducts for sources of salivary flow obstruction and to help manage salivary duct stones, stenosis, mucus plugs, or strictures. In the pediatric population, sialendoscopy is most commonly used to help in patients with sialadenitis and to avoid more invasive treatments such as sialadenectomy [3].

Potential appropriate patients for consideration for sialendoscopy include those presenting with recurrent sialadenitis. These patients typically describe recurrent pain or swelling of the major salivary glands which can be exacerbated during eating. Some patients will note foul-tasting discharge in the mouth. Acute sialadenitis is typically managed with hydration, gland massage, sialogogues, and oral or intravenous antibiotics. Acute infection is a relative contraindication for sialendoscopy.

The most common pathologies treated with sialendoscopy in the pediatric population are recurrent sialadenitis with or without stones. The aim of this review is to discuss evaluation, workup, indications, and outcomes for sialendoscopy in children.

Patient Evaluation

Careful selection of patients who may benefit from sialendoscopy is key to successful outcomes. During evaluation, a complete history is taken to assess disease severity including symptom frequency and duration and number of courses of antibiotic therapy. A family history of autoimmune disease may lead to referral to an immunologist for further workup to rule out such disease processes as Sjogren’s syndrome.

Clinical exam includes a thorough evaluation of the head and neck with palpation of the glands, assessment of salivary flow from Wharton’s and Stensen’s ducts, and bimanual palpation for palpable salivary duct stones.

Imaging is also an important part of the evaluation of a child presenting with recurrent sialadenitis. Ultrasound is the imaging modality of choice for the pediatric population, since it avoids radiation and can be performed without sedation [4]. Sialolithiasis in the parotid or submandibular ducts will appear as hyperechoic lesions with posterior shadow. Sialoliths smaller than 2 mm and those located in distal submandibular ducts within the anterior floor of mouth may not be visualized on ultrasound [5]. Findings of gland heterogeneity or dilation of the main parotid duct are associated with JRP. Ultrasound of the salivary glands is operator dependent and further cross-sectional imaging is sometimes desired. Computed tomography (CT) imaging is used to identify calcifications and evaluate for acute inflammation and abscess formation. Diffuse microcalcifications in the gland parenchyma is typical in JRP. Magnetic resonance imaging (MRI) may be more useful to evaluate for vascular malformations, lymphadenopathy, salivary neoplasms, or branchial cleft cysts but in young children has the disadvantage of requiring general anesthesia [6]. Children presenting with recurrent unilateral parotid abscess should be evaluated for possible first branchial cleft cyst.

Sialendoscopy Setup

Sialendoscopy is typically performed under general anesthesia. Nasotracheal intubation should be considered for access to salivary stones located in the posterior floor of mouth near the hilum of the submandibular gland. For Stensen’s duct, the lip and buccal mucosa are retracted toward the surgeon to straighten the course of the parotid duct. For Wharton’s duct, a bite block is placed to open the oral cavity and care is taken to identify the papilla adjacent to the lingual frenulum. Wharton’s duct papilla is smaller and more difficult to cannulate than Stensen’s duct papilla. The papilla is serially dilated using dilator sets, lacrimal probes, or silastic dilators over a guidewire, taking care to avoid trauma to the mucosa around the papilla. Sialendoscope outer diameter sizes range from 0.89, 1.1, 1.3, to 1.6 mm (Karl Storz Endoscopy, El Segundo, CA). Each scope has an irrigation channel. The scopes 1.1 mm or larger have a working channel that allows for various microinstruments to be placed into the duct lumen. During sialendoscopy, saline irrigation through the scope is used to dilate the ducts. Care should be taken to avoid excessive irrigation to prevent soft tissue swelling that may lead to soft tissue edema and airway obstruction especially in young children.

Diagnostic Sialendoscopy

For diagnostic evaluation, the smallest 0.89 mm sialendoscope without a working channel may be used. Pathology within the salivary ducts may include thick debris or mucus plugs indicative of duct inflammation or chronic obstruction. Salivary duct calculi are found within the ducts and may be mobile or impacted against the duct walls. Focal strictures can be seen and webs or diaphragmatic membranes across a portion of the duct.

Sialolithiasis

Sialolithiasis is an uncommon cause of sialadenitis in children and the pathogenesis is not well understood [7,8,9,10,11,12,13,14,15]. Theories including intermittent secretion of microcalculi or migration of food debris and bacteria into the salivary ducts have been proposed. These substances then may act as a nidus for stone formation, especially in the milieu of decreased salivary flow and/or inflammation of the ductal system. Factors felt to favor submandibular sialolithiasis include the longer course of Wharton’s versus Stensen’s duct and the increased viscosity of saliva produced in the submandibular gland.

Workup

Multiple modalities have been used in the diagnosis of salivary stones including plain radiographs, CT, MR, cone-beam CT, sialography with iodinated contrast, and ultrasound [16]. Successful identification depends on the chemical composition of the stone contents as well as the size and location of the stone. Studies have shown variable rates of sensitivity and specificity with ultrasound, but there is consensus that in experienced hands, ultrasound can identify stones down to 1.5 mm [5]. The current gold standard for diagnosis of sialolithiasis remains the CT scan [13].

Treatment

In the acute setting, sialolithiasis is treated with conservative measures and antibiotics when indicated. Salivary stone removal is recommended for long-term management. Traditionally, this required sialadenectomy. Sialendoscopes have allowed gland-preserving approaches for sialolith removal with favorable stones. Sialoliths are visualized endoscopically in the Stensen’s or Wharton’s duct and captured by specialized baskets introduced through a working channel in the endoscope. For small sialoliths, the stone may be able to be removed with gentle traction through the duct papilla. For larger or impacted sialoliths, a combined transoral or more rarely, transfacial incision may be required to remove the sialolith from the duct [17]. Sialolith location can also predict the necessity for use of combined techniques for successful stone removal. Specifically, for the parotid duct, sialoliths located posterior to the masseter muscle within the hilum of the gland are difficult to access with purely endoscopic techniques and are more likely to require combined approach [18].

Outcomes

Successful sialendoscopic sialolith removal rates vary in the literature from 35 to 89% and depend on stone size, shape, location, ductal anatomy, and experience of the surgeon [19, 20]. Sialendoscopy with or without limited sialodochotomy has become the mainstay of sialolithiasis treatment [21].

Sialadenitis Without Stones or Juvenile Recurrent Parotitis

Juvenile recurrent parotitis (JRP) is the second most common salivary gland disorder in children, behind mumps [22,23,24,25,26,27]. JRP is diagnosed clinically based on recurrent episodes of nonsuppurative parotid swelling without other identifiable etiology. The clinical presentation is variable in severity and frequency. Children typically present with painful swelling of the parotid gland without overlying erythema and low-grade fever. Saliva may have a foul taste and may contain white particulates or debris on exam. Symptoms typically resolve over days to weeks. There is usually a dominance of one side, though it may be bilateral. Boys are more often affected than girls.

Etiology

Recurrent parotitis has also been associated with hypogammaglobulinemia, isolated immunoglobulin G3 deficiency, and immunoglobulin A deficiency as was seen in one patient in our study [28,29,30,31,32,33,34]. High concentrations of Streptococcus pneumoniae and Haemophilus influenzae have been isolated in the saliva of patients with JRP [35].

Some investigators have theorized that there is compromised vascularity in the salivary ducts of patients with JRP, leading to a compromise in salivary flow, stasis, and chronic inflammation [23]. Subsets of patients have been found to have mutations in a serine protease inhibitor (SPINK1) thought to be important in inhibiting proteolytic trypsin activity and tissue destruction [25]. There is also an association with HLA-B27 seropositivity [36]. Matrix metalloproteinases (MMP) 2 and 9 have been found to be elevated in saliva of JRP patients [37]. MMPs have been implicated in a variety of degenerative diseases associated with tissue destruction and remodeling.

Workup

Ultrasound and/or magnetic resonance imaging (MRI) have replaced sialography as imaging studies of choice for diagnosis of JRP [6]. Ultrasound is especially attractive in the pediatric population with the absence of need for sedation or anesthesia and the lack of radiation exposure when compared to computed tomography. Diffuse microcalcifications can be seen on imaging (Fig. 1). Sjogren’s syndrome can occur in childhood and has a presentation similar to JRP [30,31,32,33]. Typically, these children are older and have a female predominance. Laboratory testing, including ANA, SSA/SSB, and RF, may aid in diagnosis.

Fig. 1
figure 1

Magnetic resonance imaging demonstrating diffuse microcalcifications of the bilateral parotid glands

Full size image

Treatment

To date, no preventive therapy for JRP has been identified. Historically, there was a paucity of treatment options for patients with JRP [38]. Development of sialendoscopy equipment specifically tailored to pediatric patients has the ability to offer a minimally invasive treatment for JRP. Sialendoscopy allows for confirmation of the diagnosis as well as the ability to flush the ducts and/or dilate to reduce future episodes. JRP is usually self-limiting with spontaneous regression during puberty. Conservative therapies are the first line approach, including analgesia, gland massage, hydration, warm compress, and sialogogues. For persistent or severe acute episodes, antibiotics may be helpful. Sialendoscopy is also an attractive, minimally invasive option. Intraductal steroids can be applied at the completion of the procedure; however, corticosteroid use has not been well studied and the degree of improvement and time course of benefit is not known. The optimal sialendoscopic flushing solution for JRP is an area of ongoing investigation. As the etiology of JRP is further elucidated, addition of MMP inhibitors or other target-specific anti-inflammatory mediators may increase therapeutic efficacy of sialendoscopy. Pro-angiogenic agents could also potentially have a beneficial therapeutic role to improve compromised ductal vascularity.

Outcomes

Several meta-analyses and systematic reviews have confirmed feasibility of and overall clinical improvement with sialendoscopy for patients with JRP, with success rates ranging from 73 to 93% [39,40,41,42,43,44,45, 46••, 47, 48, 49••, 50••, 51]. Most studies evaluating the treatment of JRP are limited by small patient population, retrospective design, and lack of control group. Further studies comparing treatment options and long-term outcomes are necessary.

Postoperative Care, Surgical Risks, and Complications

Postoperative antibiotics are not routinely prescribed except in the rare case that pus is encountered during sialendoscopy, in which case a broad-spectrum antibiotic is generally prescribed for 7–10 days. Complication rates of sialendoscopy vary throughout the literature (2–25%) and range from temporary gland swelling to duct avulsion requiring gland removal [19]. Other surgical risks can include perforation, stenosis, recurrence of obstruction, failure to remove salivary stone or all fragments, or injury to the papilla and should be discussed with parents prior to the procedure.

Swelling of the gland after sialendoscopy is expected and can take a few days to weeks to resolve, although the majority resolve within a few hours by the time the child is discharged from the recovery room. Most children are discharged the same day as the procedure. In young children, there is a small risk of airway obstruction with excessive irrigation into the deep parotid gland or of floor of mouth edema from excessive irrigation into the submandibular gland which may warrant overnight admission for airway monitoring. Tylenol and ibuprofen and generally sufficient for postoperative pain management. Parents are also encouraged to keep their child well hydrated.

Conclusions

Pediatric salivary gland disease remains relatively rare with JRP being the most common etiology. Characteristic findings on imaging and sialendoscopy can be used for diagnosis of JRP. Sialendoscopy appears to offer a safe, minimally invasive therapeutic option for those patients in whom the frequency and severity of episodes are impacting quality of life (QOL). It enhances our diagnostic capabilities beyond traditional imaging modalities of ultrasound, CT, and MRI. It can allow for the delivery of therapeutics—irrigation of medication, dilation of stenosis, intraductal fragmentation, or localization for stone removal. Finally, sialendoscopy helps avoid more invasive treatments and the associated morbidities.