Sialendoscopy : Endoscopic Approach to Benign Salivary Gland Diseases

Sialadenitis, or recurrent salivary gland infection associated with pain and swelling of the major salivary glands, is a common presentation to emergency rooms and outpatient clinics. One of the most frequent causes of sialadenitis is obstruction in the salivary ductal system. Salivary calculi affect 1.2% of the population and account for 60-70% of salivary duct obstruction (Nahlieli 2004; Kim 2007; Bomeli 2009; Nahlieli 2006). Additional causes of obstruction to salivary flow include strictures in 25-25%, inflammation (5-10%) and other rare pathologies such as foreign bodies (1%) Conservative treatment is the first line of therapy that includes treatment with antibiotics, salivary stimulants or sialogogues, and anti-inflammatory agents. However, conservative therapy fails in up to 40% of people with sialadenitis; in which case the recommended treatment is excision of the involved salivary gland. There as several important nerves that are in close proximity to the major salivary glands. The facial nerve, motor to facial muscles, runs through the parotid glandular system. Similarly, the submandibular gland is associated with the lingual nerve that is 1sensory to the anterior two thirds of the oral tongue; marginal mandibular nerve that allows movement of the angle of the mouth; and the hypoglossal nerve, motor to the tongue. Surgical excision of the gland carries numerous risks include but are not limited to paresis or palsy of the facial nerve, lingual nerve, and hypoglossal nerve. Other complications include Frey syndrome (gustatory sweating), sialoceles, salivary fistula, xerostomia, numbness in the distribution of the greater auricular nerve, infection, and hemorrhage. Consequently, although surgical resection in experienced hands is safe, it’s often not desired due to the associated surgical risk and external scar in the neck associated with it. In 1988, salivary duct endoscopes were introduced. Since their introduction, sialendoscopes have undergone technical refinements that have been instrumental in permitting clear and high definition visualization and manipulation of the salivary ductal system. Today, salivary duct endoscopy or “Sialendoscopy” allows the minimally invasive endoscopic visualization of major salivary gland ductal system and endoscopic interventions to treat chronic sialadenitis with or without sialolithiasis.


Introduction
Sialadenitis, or recurrent salivary gland infection associated with pain and swelling of the major salivary glands, is a common presentation to emergency rooms and outpatient clinics.One of the most frequent causes of sialadenitis is obstruction in the salivary ductal system.Salivary calculi affect 1.2% of the population and account for 60-70% of salivary duct obstruction (Nahlieli 2004;Kim 2007;Bomeli 2009;Nahlieli 2006).Additional causes of obstruction to salivary flow include strictures in 25-25%, inflammation (5-10%) and other rare pathologies such as foreign bodies (1%) Conservative treatment is the first line of therapy that includes treatment with antibiotics, salivary stimulants or sialogogues, and anti-inflammatory agents.However, conservative therapy fails in up to 40% of people with sialadenitis; in which case the recommended treatment is excision of the involved salivary gland.There as several important nerves that are in close proximity to the major salivary glands.The facial nerve, motor to facial muscles, runs through the parotid glandular system.Similarly, the submandibular gland is associated with the lingual nerve that is 1sensory to the anterior two thirds of the oral tongue; marginal mandibular nerve that allows movement of the angle of the mouth; and the hypoglossal nerve, motor to the tongue.Surgical excision of the gland carries numerous risks include but are not limited to paresis or palsy of the facial nerve, lingual nerve, and hypoglossal nerve.Other complications include Frey syndrome (gustatory sweating), sialoceles, salivary fistula, xerostomia, numbness in the distribution of the greater auricular nerve, infection, and hemorrhage.Consequently, although surgical resection in experienced hands is safe, it's often not desired due to the associated surgical risk and external scar in the neck associated with it.In 1988, salivary duct endoscopes were introduced.Since their introduction, sialendoscopes have undergone technical refinements that have been instrumental in permitting clear and high definition visualization and manipulation of the salivary ductal system.Today, salivary duct endoscopy or "Sialendoscopy" allows the minimally invasive endoscopic visualization of major salivary gland ductal system and endoscopic interventions to treat chronic sialadenitis with or without sialolithiasis.
As in many other surgical areas, the advent of sialendoscopy has added additional options to the diagnosis and management of non-neoplastic salivary pathology.Initially, sialendoscopy was created for diagnostic evaluation of the salivary glands and ductal system as well as treatment of obstruction through the removal of sialoliths or dilation of strictures.Nahlieli et al, in their study in 2004 1 described successful endoscopic treatment of recurrent parotitis and juvenile recurrent parotitis.The scope of sialendoscopy was further expanded to treat radioactive iodine sialadenitis (Kim 2007;Bomeli 2009;Nhlieli 2006) and sialadenitis induced by autoimmune diseseases (Schacham 2011).Today, sialendoscopy is regarded as an acceptable and often preferred diagnostic and treatment tool for chronic sialadenitis and non-neoplastic obstruction of the salivary ductal system.

Indications and contraindication
Current evidence has validated sialendoscopy for the treatment of non-neoplastic disorders of the salivary glands, including sialolithiasis.Sialolithiasis is one of the most common nonneoplastic disorders of the major salivary glands and a major cause of sialadenitis and unilateral diffuse swelling of the major salivary glands (Marchal F, Dulguerov P. 2003;Nahlieli O. 2006).In general, stones less than 4 mm in the submandibular gland and less than 3 mm in the parotid gland are amenable to endoscopic removal.Intermediate size stones between 5-7 mm may need further fragmentation either using a Holmium laser or lithotripsy prior to endoscopic extraction.In general stones larger than 8 mm require a combined approach technique for stone removal (Karavidas K, Nahlieli O, Fritsch N, et al. 2010).The combined approach technique is a technique that uses the sialendoscope for stone localization and either an intra-oral or an external approach for removal of large submandibular or parotid gland stones, respectively (Bodner L. 2002 The only absolute contraindication is acute sialadenitis.The use of the rigid dilator system and/or a semi-rigid endoscope during an acute episode increases the chance of ductal trauma and irrigation as well as ductal injury could increases the potential spread of infection in the head and neck soft tissues.Sialendoscopy can be challenging in patients with microstomia or trismus.These could be considered as relative contraindications for the procedure.

Sialendoscopy: Technique
Sialendoscopy may be performed in the clinic setting with local anesthesia or in the operating room with sedation or general anesthesia.The decision of where to perform the procedure is physician and/or patient preferences.The basic work up for sialendoscopy is summarized in Table 1.

Basic workup
Workup of all salivary disorders begins with history of present disease.Important questions to ask include symptoms, number of infections, previous treatments, and previous testing or other studies.Questions regarding history of external beam radiation or radioactive iodine therapy are important as well to understand possible etiologies of salivary disease.
Examination should first include a complete head and neck exam.Bimanual palpation of the salivary gland should be performed to examine for any masses or palpable stones, noting any asymmetry.Examine the papilla and its location.Assess the patency and saliva flow and quality of the saliva from the papilla.It is important to make notes regarding the papilla in the chart to aid in identification when ready to perform sialendoscopy; pictorial illustrations are particularly helpful.In addition, the surgeon must evaluate access to the oral cavity by paying close attention to the size of the oral commissure (e.g., microstomia), size of tongue, ability to open the mouth (e.g., preoperative trismus), and pathology of temporomandibular joints Laboratory and imaging studies ordered will depend on the patient's symptoms and physical exam findings.Frequently used imaging studies include ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI), (Figures 1 and 2).The authors' preference for diagnosis and surgical planning is CT scan with and without contrast.

Instrumentation
The basic instrumentation includes a specialized dilator system that permits gradual serial dilation of the salivary duct papilla from the lowest No.0000 dilator to a maximum of No.8, (Figure 3).The sialendoscopes most frequently used are the "all-in-one" interventional sialendoscopes, which can range from 1.1.mmto 1.6 mm in diameter, (Figure 4).The sialendoscopes have an optic channel that transmits the image using fiberoptic channels, and an irrigation channel allows a continuous irrigation to be performed to maintain duct patency for endoscopic visualization of the salivary duct lumen and to allow working space for surgical intervention.A working channel is used to introduce instruments for intervention.The 1.1 and 1.3 mm sialendoscopes permit introduction of 0.4 mm stone wire baskets (Figure 5 A-C) and a hand-held micro burr to break stones.The 1.6 mm sialendoscope permits the use of 0.6 mm stone wire basket and a cup forceps in addition.Holmium laser fibers can be used as well through the interventional channels for intraductal laser fragmentation of stones, (Figure 6).Another important tool for sialendoscopy is the conical dilator that permits gradual dilation of the duct and allows one to transition from a smaller dilator to the next size, (Figure 7).

Operative technique
Operative technique can be divided into two main components: 1. Access to the salivary duct i.e. dilation of the papilla 2. Endoscopy with or without intervention.Management of papilla is the rate-limiting step of the procedure.Care must be taken to dilate the papilla.Poor handling of the papilla can lead to papillary stenosis in the future that can lead to obstructive sialadenitis.In addition, perforation of the duct (minor or major ductal tear) and creation of a false passage are potential complications of papilla dilation that add morbidity to the procedure and also are reasons for sialendoscopy failure.Identification of the papilla can be aided by a using an operating microscope or surgical loupes.The author recommends the use of at least surgical loupes to identify and dilate the papilla.In office localization and documentation of the location of the papilla with imaging is very helpful in intra-operative identification of the papilla.Massage of the gland may also assist in localizing the papilla by denoting the point of saliva flow.After identification of the papilla, serial dilation of the papilla is then performed using the Marchal dilator system, (Figure 3).Injection of local anesthetic around the papilla often helps the process of serial dilation by making the ductal opening more prominent and by stiffening the surrounding tissues to facilitate serial cannulation of the duct.In this procedure, salivary probes of increasing diameter, beginning with the smallest (No. 0000), are sequentially introduced into the duct.Dilation up to No.  Nahlieli et al have suggested performing a papillotomy to allow introduction of the scope (Nahlieli O. 2006).However, in the authors' experience, a papillotomy prevents the creation of a mucosal seal around the endoscope, resulting in leakage of the irrigation, consequently preventing maximum dilation of the duct through hydraulic pressure.The authors reserve the use of a papillotomy for one of two scenarios: difficult cases in which standard dilation or the Seldinger's technique fails and if necessary for the delivery of larger stones at the conclusion of a procedure.

Endoscopy with or without intervention
Despite its apparent simplicity, sialendoscopy is a technically challenging procedure that requires organized and sequential learning (Marchal F. 2003).Once this is acquired, the success rates for diagnostic as well as interventional sialendoscopy can be more than 85% (Marchal F, Dulguerov P. 2003;Nahlieli O. 2006;Marchal F. 2003).
Sialendoscopy allows visualization of the entire ductal system with ability to navigate the scope into primary, secondary and at time tertiary branching systems, (Figure 10).With respect to diagnostic sialendoscopy, Marchal and Dulguerov reported a 98% success rate (Marchal F, Dulguerov P. 2003), whereas (Nahlieli O, Baruchin AM. 1999) reported a success rate of 96% in their case series.Though diagnostic sialendoscopy is possible in most patients, failure to pass the scope along the entire ductal system may result from ductal stenosis, inflammation, or because of the presence of an acute masseteric bend of the parotid duct, making navigation with the scope difficult.For larger stones or stones that cannot be accessed endoscopically, a combined approach technique is required, (Figure 11).The use of the da Vinici robot has been described to assist in the

Complications
Major complication rates are low with sialendoscopy.

Future directions and conclusions
Diagnostic and interventional sialendoscopy are safe and effective options for treating nonneoplastic disorders of the major salivary glands.Sialendoscopy is technically challenging and requires sequential learning in which success rates appear to be proportional to the surgeon's level of experience Marchal F, Dulguerov P. (2003).The authors recommend that future sialendoscopist's should familiarize themselves with the anatomy and physiology of the salivary glands and floor of the mouth.They should be competent in taking care of any potential complication and should be comfortable with major salivary gland resections if required.Sialendoscopy training via hands-on courses and case observations should be pursued prior to initiating a sialendoscopy practice

Fig. 1 .
Fig. 1.Ultrasonography image of large submandibular stone.The stone appears as a hyperechoic rim while throwing a shadow that is a pathognomic finding of a salivary stone visualized via ultrasound, (black arrow points to the stone).

Fig. 2 .
Fig. 2.An contrast enhanced axial CT scan showing a large irregular left submandibular stone in the hilum, (the asterix denotes the salivary stone).

Fig. 7 .Fig. 8 .
Fig. 7. Conical Dilator 3 or No.4 is adequate to allow introduction of a sialendoscope of 1.3mm diameter.For the introduction of larger endoscopes (1.6mm), dilation up to No.6 probe is necessary(Marchal F. 2003).Other techniques used to dilate the papilla or facilitate the identification of the papilla are the Seldinger's technique that uses a series of bougies of increasing diameter that are inserted over a guide wire that is placed in the salivary duct (Figure9), the placement of a papillotomy or an incision at the entry point of the salivary duct to facilitate entry into the it, and use of Methylene blue to identify the duct orifice(Marchal F. 2003; Geisthoff UW. 2009; Papadaki ME, Kaban L, Kwolek C, et al. 2007; Iwai T, Matsui Y, Yamagishi M, et al. 2009; Luers JC, Vent J, Beutner D. 2008).

Fig. 9 .
Fig. 9. Bougies of increasing diameter used in the Seldinger's technique of salivary duct dilation.

Table 1 .
Preoperative Evaluation between 50 and 100%.Failure is most commonly due to severe ductal stenosis(Kim JW, Han GS, Lee SH et al. 2007; Bomeli SR, Schaitkin B, Carrau RL, et al. 2009; Nahlieli O and Nazarian Y. 2006).Juvenile recurrent sialadenitis most frequently affects the parotid gland.The etiology is unknown.Sialendoscopy can be used as both a diagnostic tool and treatment (Nahlieli O, Shacham R, Shlesinger M, et al. 2004; Jabbour N, Tibesar R, Lander T, et al. 2010; Martins-Carvalho C, Plouin-Gaudon I, Quenin S, et al. 2010; Faure F, Querin S, Dulguerov P, et al. 2007).Sialendoscopy with irrigation of the duct with or without injection steroids has been shown to be effective in treating this condition.Characteristic findings are seen on sialendoscopy originally include whitish appearance of the duct and lack of vascular markings seen on the ductal wall.Shacham et al. (Shacham R, Droma EB, London D, et al. 2009) studied 70 children with recurrent sialadenitis.In 56 of the children, symptoms were eliminated after one procedure; only 5 children required a repeat procedure.
(Nahlieli O. 2006st-operatively is expected and usually resolves in approximately 24-48 hours.This is particularly important to consider in submandibular procedures, as swelling could cause airway compromise (Iwai T, Matsui Y, Yamagishi M, et al. 2009).Consequently, when performing bilateral submandibular gland procedures, it is important to examine the gland and oral cavity after completing one side and determine whether it is safe for the patient to proceed with the contralateral gland.One of the more serious iatrogenic complications is avulsion of the duct.This complication can be prevented by avoiding excessive traction on the stone while it is engaged in the wire basket,.If duct avulsion or a major ductal tear occurs, subsequent gland excision could be necessary(Walvekar RR, Razfar A, Carrau RL, et al. 2008).Lingual nerve paresthesias can occur in up to 15% of patients undergoing transoral combined procedures in the immediate post-operative period and resolves with time (Walvekar RR, Razfar A, Carrau RL, et al. 2008; Bowen MA, Tauzin M, Kluka, EA, et al. 2010; Nahlieli O. 2009).The development of a post-operative stricture has been reported (Bowen MA, Tauzin M, Kluka, EA, et al. 2010; Nahlieli O. 2009).Taking care not to cause trauma to the duct or papilla during the procedure minimizes the risk of this complication.In addition, in the event the duct is traumatized or a papillotomy is required, placement of a salivary stent for up to 2 weeks can help prevention of subsequent ductal or papillary stenosis.Salivary fistulas, sialoceles, minor ductal tears, development traumatic ranulas, minor bleeding, and infection have been reported(Nahlieli O. 2006; Walvekar RR, Razfar A, Carrau RL, et al. 2008; Bowen MA, Tauzin M, Kluka, EA, et al. 2010) (4,21,31).Other complications may include inability to retrieve the stone and failure of the procedure due to ductal stenosis or an acute masseteric bend (Nahlieli O. 2006; Walvekar RR, Razfar A, Carrau RL, et al. 2008; Bowen MA, Tauzin M, Kluka, EA, et al. 2010; Nahlieli O. 2009).