Technology of Sialendoscopy




Technical developments have taken place since the first endoscopes suitable for sialendoscopy appeared. Now, a variety of endoscopes are available. Ranging from rigid to flexible, each type has its own properties. Light sources, imaging, recording instrumentation, and other equipment used with the endoscopes facilitate or extend the range of their use. Experiences using different endoscopes in more than 300 endoscopies are discussed.


The diameter of salivary ducts sets a limit on the size of the instruments that can be used within them. The miniaturization of endoscopes finally allowed sialendoscopy to begin in 1988 ( Fig. 1 ). Multiple considerations are needed to adapt endoscopes to the salivary ducts and glands, including compact outer diameter, highest number of pixels, durability, effective cleaning and sterilization, large working channel for various instruments, ergonomic handling, and flexible maneuverability inside the duct system.




Fig. 1


Flexible endoscope (Olympus, Tokyo, Japan) used by Philippe Katz for the first salivary gland endoscopy in December 1988. ( Courtesy of Dr Philippe Katz, Paris, France; with permission.)


Types of endoscopes and their properties


Different types of endoscopes have emerged to meet the demands listed previously: flexible sialendoscopes, rigid sialendoscopes, and semiflexible sialendoscopes (compact and modular). Table 1 lists different models of sialendoscopes from the past and present. Box 1 lists the addresses of different producers and distributors for material usable for sialendoscopy. Each type of endoscope has its own clinical properties.



Table 1

Overview of different historic and current endoscopes
























































































































































































































































































































Author, Year, no. of Pixels, Additional Information Type of Endoscope Compact/Modular/Steerable Flexible Manufacturer/Distributor Outer Diameter/mm Diameter of the Working Channel/mm Diameter of the Irrigation Channel/mm
Gundlach 1990 Flexible Unknown Richard Wolf 2 0.6 Only one channel
Königsberger 1990 Flexible Steerable Karl Storz Unknown >0.8
Katz 1991 Flexible Olympus (Tokyo, Japan) 0.8 None
Arzoz 1994 Rigid Unknown Karl Storz 2.3 1 Only one channel
Gundlach 1994 Flexible 1.5 0.5
Nahlieli 1994 Rigid Modular Friatec (Mannheim, Germany) 2.9 None 2.9–2.7
Zenk 1994 Flexible Steerable 1.6 >0.4
Iro 1995 Flexible Steerable 1.6 0.6 Only one channel
Ito 1996 Flexible Clinical Supply (Japan) 1.5 0.2
Iro 1996 Flexible Steerable 1.5–2.0 >0.4 0.2
Arzoz 1996 ? Karl Storz 2.1 1.0
Yuasa 1997 Flexible Medical Science (Tokyo, Japan) 0.8 None
Yuasa 1997 Rigid Medical Science 1.0 None
Nahlieli 1997 Rigid 2.0 1.0
Nahlieli 1997 Rigid 2.5 1.0
Hopf 1998 Flexible Steerable ? 1.6 0.5 Only one channel
Marchal 1998 ? ? 0.9–1.6
Nahlieli 1999 Semirigid Karl Storz 1.3 None 1.3–1.0
Nahlieli 1999 Semirigid Karl Storz 2.3 × 1.3 1.0 1.3–1.0
Kerr 2001 Rigid Richard Wolf 1.5 ? ?
Marchal 2001 Flexible Nonsteerable 0.5–0.8 None None
Marchal 2001 Semirigid Modular Karl Storz 1.3 None 1.3–1.0
Marchal 2001 Semirigid Modular Karl Storz (2.67 mm 2 ) 0.8 +
Marchal 2001 Semirigid Modular Karl Storz (2.29 mm 2 ) 0.8 +
Chu 2003 Rigid 3.1 +
Zenk 2004 6000 px Semirigid Compact PolyDiagnost 1.1 0.4 +
Geisthoff 2007, 2008, 6000 px, a Semirigid Compact Gyrus ACMI/Spiggle & Theis 1.7 1.0 0.2
Nahlieli 2007, Iro 2008, 6000 px, a Semirigid Compact Karl Storz 0.8 – 0.25
Nahlieli 2007, Iro 2008, 6000 px, a Semirigid Compact Karl Storz 1.1 0.4 0.25
Nahlieli 2007, Iro 2008, 6000 px, a Semirigid Compact Karl Storz 1.6 0.8 0.26
6000 px Semirigid Modular PolyDiagnost 0.9, 1.1, 1.6, 2.0 One-joint working and irrigation channel also containing the optical system (0.53 mm)
10,000 px (one version with opening angle of 70° and one of 120°) Semirigid Modular PolyDiagnost 1.1, 1.6, 2.0 One-joint working and irrigation channel also containing the optical system (0.9 mm)
30,000 px Semirigid Modular PolyDiagnost 1.6, 2.0 One-joint working and irrigation channel also containing the optical system (1.2 mm)
6000 px, a Semirigid Compact Spiggle & Theis 0.9 None 0.26
6000 px, a Semirigid Compact Spiggle & Theis 1.0 0.41 0.2
6000 px, a Semirigid Compact Spiggle & Theis 1.2 0.62 0.2
6000 px, a Semirigid Compact Spiggle & Theis 1.4 0.62 0.3
6000 px Flexible Steerable Spiggle & Theis 1.3 One-joint working and irrigation channel of 0.35 mm

Abbreviations: a, suitable for autoclave; px, pixels/number of fibers in the optical transmission system; ?, unknown; +, containing such a channel of unknown diameter; −, not containing such a channel.


Box 1





Companies selling or producing technology that might be used for sialendoscopy


Flexible Endoscopes


Flexible endoscopes are advantageous as it is possible to move them through ductal kinks and bends. Some of the flexible endoscopes can be steered, which is especially helpful when a certain branch has to be intubated (see Fig. 1; Figs. 2–5 ). Their use is atraumatic; however, a drawback is that only weak forces can be applied (eg, to surmount stenotic areas). Handling is often more difficult than for semirigid or rigid endoscopes. The success rate for normal stones seems to be lower than for semirigid endoscopes. Flexible endoscopes are fragile and have a short lifespan and it is not possible to autoclave them.




Fig. 2


Historic flexible endoscope without steering and without working channel similar to the one used by Katz in 1988. ( Courtesy of Richard Wolf, Knittlingen, Germany.)



Fig. 3


( A ) Self-made construction to allow irrigation for the endoscope shown in Fig. 2 . ( B ) Modern flexible nonsteerable endoscope with 3000 fibers primarily sold for endoscopy of the lacrimal ducts and the eustachian tube. ( Courtesy of Karl Storz, Tuttlingen, Germany.) ( C ) To allow steering of such a flexible endoscope, rigid outer sheaths can be used. A functionality similar to the mother-baby endoscopes used in gastroenterology results. These systems, however, are extremely fragile and expensive.



Fig. 4


Modern flexible steerable endoscope with 6000 fibers, an outer diameter of 1.5 mm, and a working channel of 0.4 mm. ( Courtesy of Spiggle & Theis, Overath, Germany.)



Fig. 5


The tip of the endoscope shown in Fig. 2 can be bent to facilitate changing the direction of view, passing curves and kinks.


Rigid Endoscopes


Most clinical endoscopes rely on a fiberoptic system for image transmission. Rigid endoscopes, however, use a pure lens system with superb optical qualities and better resolution. These endoscopes have larger diameters but are more stable ( Fig. 6 ). They can be autoclaved. The camera is fixed directly onto the ocular attached to the endoscope, resulting in a cumbersome handling.




Fig. 6


Rigid endoscope together with a sheath that allows irrigation. ( Courtesy of Richard Wolf, Knittlingen, Germany.) Endoscopes of this type are also used for arthroscopies or pediatric cystoscopies. No working channel is provided. One possibility for interventions is to remove the optics from the irrigation channel in the moment when the target has been reached. Afterwards, instruments can be introduced and operations be performed under haptic control.


Semirigid Endoscopes


Semirigid endoscopes are a compromise between flexible and rigid endoscopes. The long, flexible, optical fiber connection for light and image transmission enables the decoupling of the examination probe from the rigid eyepiece. This means that work with semiflexible endoscopes can be performed with great freedom of movement and minimal effort while maintaining excellent precision. A modular and a compact construction type of semirigid endoscopes exist.


Semirigid Compact Endoscopes


A typical therapeutic semirigid compact endoscope combines a fiber light transmission, a fiber image transmission, a working channel and an irrigation channel within one compact instrument ( Fig. 7 ). The outer tube covers, stabilizes, and protects all of the components resulting in a minimum outer diameter of the whole system. Fig. 8 shows the construction principle of the sheath of the examination probe of a semirigid compact endoscope and Figs. 9–11 show enlarged the tips of such endoscopes.




Fig. 7


Example of a compact semirigid endoscope (instrument according to Geisthoff, Spiggle & Theis, Overath, Germany). This therapeutic endoscope has a working channel of 1 mm, which also allows the introduction of quite stable forceps (as shown). The existence of the irrigation channel (diameter of 0.2 mm) can be noted by the second Luer lock tube at the back part of the endoscope. The endoscope has a large outer diameter of 1.7 mm; therefore, Seldinger’s technique often has to be applied for insertion (see also article by Geisthoff on “Basic Technology of Sialendoscopy” elsewhere in this issue).



Fig. 8


Construction principle of a compact semirigid endoscope. One outer tube protects and stabilizes all internal components, including fiber optics and working and irrigation channels. In this case, the diagnostic endoscope contains only an irrigation and no true working channel. ( Courtesy of Spiggle & Theis, Overath, Germany; with permission.)



Fig. 9


Microscopic view of a tip of a therapeutic compact semirigid endoscope similar to the one shown in Fig. 7 . The fibers of the image transmitter are covered by a lens, whereas the optical fibers for the light source are filling the gaps between the outer tube, the image transmitter, and the working and the irrigation channel. ( Courtesy of Spiggle & Theis, Overath, Germany; with permission.)



Fig. 10


Enlarged tip of a diagnostic semirigid endoscope as shown in Fig. 8 . When comparing to Figs. 7 and 9 , it can be clearly seen that there is only an irrigation but no working channel (outer diameter: 0.9 mm). ( Courtesy of PolyDiagnost, Pfaffenhofen, Germany; with permission.)



Fig. 11


Enlarged top of a diagnostic semirigid endoscope similar to the one shown in Fig. 10 . The form of the irrigation channel is oval instead of round for further miniaturization (outer diameter: 0.7 mm). ( Courtesy of PolyDiagnost, Pfaffenhofen, Germany; with permission.)


Semirigid Modular Endoscopes


The optical fibers used for light and image transmission are combined into a single probe-like component ( Fig. 12 A, B). This can be used in combination with different sheaths (see Fig. 12 C). Using a small single sheath creates a diagnostic endoscope. The gap between optical system and the sheath’s outer wall is used as irrigation channel ( Fig. 13 ). A combination with a large single lumen sheath or a double-lumen sheath creates enough space to introduce different instruments ( Fig. 14 ).




Fig. 12


( A ) Probe-like optical system of a modular semirigid endoscope. The probe-like sheath includes the fibers for the light source and the image-transmission system (instrument according to Nahlieli, Karl Storz, Tuttlingen, Germany). ( B ) Probe-like optical system of a modular semirigid endoscope. The covering of this version is made from nitinol steel giving it high flexibility and low risk of breakage. ( Courtesy of PolyDiagnost, Pfaffenhofen, Germany; with permission.) ( C ) Different sheaths with diameters of 0.9 mm, 1.1 mm, 1.6 mm, and 2.0 mm for the optical system shown in Fig. 12 B. These sheaths are single use only; a version for autoclave also exists. A disadvantage of this system is that air is sometimes entrapped in the sheaths and can be annoying during the endoscopy. ( Courtesy of PolyDiagnost, Pfaffenhofen, Germany; with permission.)



Fig. 13


( A ) The combination of the optical system shown in Fig. 12 A with one simple sheath results in a diagnostic endoscope with only one irrigation channel. ( From Karl Storz, Tuttlingen, Germany; with permission.) ( B ) Combination of the optical system shown in Fig. 12 B and a sheath with an outer diameter of 0.9 mm. A diagnostic endoscope with irrigation channel but without working channel results. ( Courtesy of PolyDiagnost, Pfaffenhofen, Germany; with permission.)



Fig. 14


( A ) The combination of the same optical system shown in Fig. 12 A with a double-tube–like sheath makes an interventional endoscope with irrigation and working channel. Different sizes of working channels for different tasks can be chosen, making this a versatile instrument. ( From Karl Storz, Tuttlingen, Germany; with permission.) ( B ) When combining the optical system shown in Fig. 12 B with a larger sheath, an interventional endoscope results. In this case, a sheath with an outer diameter of 1.1 mm was used; a 0.4-mm basket was introduced through the common working and irrigation channel. ( From PolyDiagnost, Pfaffenhofen, Germany; with permission.)


In comparison with the compact versions, the ratio of the working channel to the total endoscope diameter is usually lower in modular endoscopes. The single therapeutic outer sheaths of modular endoscopes sometimes trap air, which can impair visualization by irrigating into the ducts. The modular systems, however, have two important advantages:




  • 1. Economic advantage: only one optical system is necessary for a variety of procedures. The optical system is the most expensive part of the endoscope. By combining it with different sheaths, a versatile tool is created.



  • 2. Hygienic advantage: compact endoscopes often have very thin irrigation channels. These are difficult to clean. Plasma sterilization may not be sufficient for these narrow channels, gas sterilization is often not available, and autoclaving can damage the endoscope. The probe-like optical system of modular endoscopes is easy to clean and is normally suitable for plasma sterilization. The channels of the different sheaths generally have larger diameters and the sheaths themselves are normally autoclavable or single use only.



Outer Diameter, Shape, Material, Maneuverability


The outer diameter is of paramount importance for the introduction of the scope and its advancement inside the narrow duct system. The endoscopes with diameters of approximately 1.5 mm and larger are sometimes not thin enough to accommodate the ducts and might not advance the pathology. In such cases, other approaches, such as sonographically controlled procedures, should be taken into consideration. Modular semiflexible endoscopes are produced with two different cross-sectional shapes: the round version conforms well with the round shape of the duct. The outer shape of a double tube uses the same perimeter of the duct for a lower cross-sectional area. The unused space between the two tubes, however, also has advantages: it can be used to flush fragments or debris with irrigation to clear the field of view. This space also allows for higher flow and passage of larger particles. For other large round endoscopes, it is sometimes necessary to interrupt endoscopy by removing the scope and massaging the gland to clear the duct system.


Some endoscopes are made from nitinol steel (see Fig. 12 B; Fig. 15 ), which is more flexible than regular steel and can be advantageous when following a curved duct. A more rigid system, however, is often easier to steer. Again, outer diameter also plays an important role here.




Fig. 15


Compact modular semirigid interventional endoscope made with outer tubing from nitinol steel. This gives a high flexibility and a lower risk of breakage. The flexibility is sometimes advantageous during interventions; sometimes more rigid instruments are better for steering. ( Courtesy of PolyDiagnost, Pfaffenhofen, Germany; with permission.)


An interesting feature of one compact semirigid endoscope series (Marchal model, Karl Storz) is a slight bend in the endoscope shaft near its distal tip ( Fig. 16 ). This can make steering and selectively following branchings easier. The bend does reduce the usable diameter of the working channel, however, and prevents the use of straight, nonflexible instruments.




Fig. 16


Compact modular semirigid interventional endoscope according to Marchal with a slight curve at the distal tip. This bend can be advantageous when following a curve duct or trying to intubate a ductal branching. ( Courtesy of Karl Storz, Tuttlingen, Germany; with permission.)


In most cases, the intraductal position of the endoscope tip can be easily seen by skin transillumination. Centimeter markings on the shaft, however, can help to assess exactly the tip’s position (Erlangen model, Karl Storz) ( Fig. 17 ).




Fig. 17


Compact modular semirigid interventional endoscope, Erlangen type, with centimeter markings on the sheath. In addition to the transillumination effect, these markings can be helpful to assess the current position of the tip of the endoscope. ( Courtesy of Karl Storz, Tuttlingen, Germany; with permission.)


Good maneuverability is also achieved by flexible, steerable, fine endoscopes. These endoscopes are mainly used for diagnostic purposes but do have a “working channel” in some models (Spiggle & Theis and Almikro) mainly for irrigation. Such models are of limited use for stone fragmentation and extraction as only fine baskets fit through the working channels. The use of laser fibers is limited as they are often not resistant to strong bending and break. The increase in combined endoscope approaches might give these instruments some more importance: a small, flexible, steerable endoscope is more likely to reach a stone in a curved duct system than a semirigid one. It can be used to mark the stone by the transillumination effect, so that it can be approached externally. Maneuvering a flexible steerable endoscope, however, often requires more skill and experience than a semirigid one.


Working Channel Diameter


The diameter of the working channel is of paramount importance for some therapeutic tasks. Table 1 gives an overview of the diameters of instruments used in therapeutic endoscopies. It is important to realize the effect of the diameter on the stability of the instruments. For instruments, such as forceps, balloons, or baskets, the cross-sectional area of a 0.4-mm diameter instrument is one quarter that of a 0.8-mm diameter instrument. The cross-sectional area of the latter one is 0.64 the size of a 1-mm diameter instrument. The rate of success and the risk of material fatigue breakage of the instruments are directly correlated with cross-sectional area. Additionally, the finer instruments are often more expensive. Alternatively, a large, stable instrument is of no use when it is too large to reach the relevant duct region. Sophisticated instruments in this respect are the so-called optical forceps, which are a combination of an outer sheath with an incorporated instrument (PolyDiagnost, Pfaffenhofen, Germany) ( Figs. 18 and 19 ). These instruments allow the effective use of forceps in combination with a small overall diameter of the whole instrument. Minor drawbacks of this system are that the forceps can impede vision during endoscope advancement. Additionally, a change of the instrument always means complete removal of the endoscope, a change-out of the instrument, and then its reinsertion.


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Apr 2, 2017 | Posted by in OTOLARYNGOLOGY | Comments Off on Technology of Sialendoscopy

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