Introduction
Diagnostic sialendoscopy is fundamental in the assessment and the treatment of salivary gland ductal pathology. Because of this diagnostic modality, the main duct, secondary, and tertiary branches can practically all be explored and evaluated. Diagnostic sialendoscopy can either be done as a single procedure or it can be incorporated in a more complex surgery involving combined or purely endoscopic approaches.
Diagnostic sialendoscopy must not be viewed as a minor part of a surgery performed only at the beginning of these combined or purely endoscopic procedures. It is a dynamic tool during the different parts of the surgery. For example, after removing a submandibular hilar stone transorally, it is paramount to proceed with a proximal endoscopy to evaluate for residual stones or stenosis that need to be addressed.
The purpose of this chapter is to: (1) help distinguish the gross and subtle differences between inflammatory salivary gland disorders evaluated with diagnostic sialendoscopy; (2) offer technical maneuvers to improve the chances of correct diagnosis; and (3) assess and predict the chances of success of interventional sialendoscopy.
Choosing the Appropriate Endoscope for Diagnostic Sialendoscopy
All sialendoscopes can adequately perform diagnostic sialendoscopy. It is important to understand the advantages and disadvantages of each endoscope. Endoscopes are roughly divided into two categories: the all-in-one system (Marchal and Erlangen sets, Karl Storz, Tuttlingen, Germany) and the modular system (Marchal Modular set, Karl Storz). The former has integrated rinsing and operating channels (the operating channel is absent in the endoscopes that have a diameter <1 mm). The latter consists of a nude optic fiber (0.75 or 1 mm in diameter), which is inserted into an examination or operating sheaths. The examination sheath only has a rinsing channel, whereas the operating sheaths have an additional operating channel.
For purely diagnostic sialendoscopy, surgeons prefer to start with the smallest endoscopes. The obvious advantage of smaller endoscopes is that they can easily be inserted inside the duct once the papilla has been dilated. In addition, they can navigate through smaller ductal branches and stenosis with more ease. There are basically seven endoscopes that can be used at the start of a case: the 0.8 mm and 1.1 mm (Erlangen all-in-one set), the 0.89 mm, 1.1 mm and 1.3 mm (Marchal all-in-one set) and the 0.75 mm and 1 mm modular endoscopes with their corresponding examination sheaths. The 0.75 mm and 1 mm modular endoscopes are traditionally used in the parotid and submandibular glands, respectively. The main advantage of the 1.1 mm and 1.3 mm endoscopes is that a guidewire can be inserted through the operating channel. The guidewire can only be inserted through the operating channel of the operative sheaths of the modular endoscope. The choice of the endoscope ultimately depends on the preference and experience of the surgeon.
Diagnostic Evaluation of the Salivary Gland Ductal System
The purpose of diagnostic sialendoscopy is to characterize, as much as possible, the cause of the ductal obstruction. The endoscopic findings can be divided in three categories: sialolithiasis, stenosis, and inflammatory. The first two are causal obstructive factors, and the third one, an epiphenomenon. One should keep in mind that the endoscopic findings during diagnostic sialendoscopy are important clues that lead the surgeon to decide what is the best surgical approach.
Sialolithiasis
Salivary stones account for 80–90% and 5–28% of all cases of submandibular and parotid gland sialadenitis, respectively. Salivary stones are characterized by their localization, number, size, aspect, shape, mobility, visibility during endoscopy, and palpability. The interaction of all these factors will influence the success or failure of a procedure. Preoperative computed tomography (CT) and/or ultrasound are important, as it will give information on the localization, the number, and size of a stone. However, it is possible, to a certain extent, to gather the same information during endoscopy.
Localization of a stone can be achieved either by endoscope transillumination of the floor of the mouth for the submandibular gland or of the skin (or SMAS) for the parotid gland ( Fig. 16.1 ). The number of stones is assessed through direct visualization. Endoscopy can, in certain cases, be more precise than preoperative imaging.
Determining the size of a stone is very important and can be estimated with endoscopy. Trying to retrieve a 4–5 mm non-palpable hilar submandibular stone with a basket will probably injure a 3 mm Wharton’s duct canal. Thus, having a good appreciation of the size of a stone is relevant. In this case, either endoscopic laser lithotripsy or floor of mouth exploration would be the best surgical approaches from a gland-preserving perspective. The guidewire’s diameter is an easy and reliable way to estimate the size of a stone. Depending on the endoscope, two types of guidewires are used: the 0.4 mm and 0.6 mm. With the tip of the wire and with direct visualization, it is possible to approximate the stone’s length and width ( Fig. 16.2 ).
The external aspect of a stone also gives valuable information. Salivary stones are composed of organic and inorganic material. The relative contribution of each varies significantly from one stone to another. There is a direct correlation between the density of the stones and their composition. In general, a friable stone will be whitish and have irregular borders, in contrast to a hard stone that will have a smooth, well-defined yellowish contour. It is much easier to achieve endoscopic lithotripsy on a friable stone than on a hard stone ( Fig. 16.3 ).
The shape of a stone is also an important consideration during endoscopy. A spindle-shaped stone can be easier to retrieve with a basket than a round stone. The diameter of a stone is more of a determining factor than its length. A 1 cm diameter round stone will be difficult to remove with endoscopy. Conversely, a 1 cm in length, 3 mm in diameter, spindle-shaped stone will be easier to retrieve with a basket, on the condition that the stone is in the same axis as the canal.
Several signs can help the surgeon quickly determine whether a stone is mobile or not. A mobile stone will move during irrigation or contact with the guidewire. Also, if a stone has a smaller size than the duct’s diameter, it will necessarily be floating ( Fig. 16.4 ). The simplest scenario corresponds to a floating stone that is seized with a basket and brought from the hilum directly to the papilla. However, the surgeon has to recognize a mobile stone behind a stenosis ( Fig. 16.5 ). The surgeon needs to be aware of the potential risk of an entrapped basket, ductal injury or even ductal avulsion if the stone is grasped and pulled towards the papilla; bear in mind the potential mismatch between the diameter of the stone and the canal.
It is also important to recognize a fully and partially visible stone during endoscopy ( Fig. 16.6 ). The latter is more challenging if any attempt at intracorporeal lithotripsy is made. The guidewire can potentially help the surgeon dislodge the stone and make it fully visible.
