Figure 3.2 Rigid endoscopes used in laparoscopy and thoracoscopy. From bottom to top: 4 mm 30°; 5 mm 0°; 10 mm 0° and 10 mm ENDOCAMELEON variable angle laparoscope.
Source: © KARL STORZ SE & Co. KG, Germany.
Standard surgical telescopes come in a variety of sizes (Figure 3.2). The most versatile and popular rigid telescopes used in small animal laparoscopy and thoracoscopy are 5 mm in diameter and approximately 30 cm in length. Smaller rigid endoscopes, 2.7 or 3 mm in diameter and 14–18 cm long are ideal for cats, puppies, and toy breeds. With a smaller diameter and shorter shaft, these are easier to maneuver in smaller patients but too short in larger patients, and their light‐carrying capacity may be inadequate in larger cavities, due to the small diameter of the telescope. Telescopes larger than 5 mm in diameter have decreased in popularity, mostly because of the improvements in image size and brightness of 5‐mm and smaller telescopes [1–5, 8, 9].
Conversely, the 10 mm diameter operating laparoscope has become popular. It contains optics similar to that of a 5‐mm telescope but has an integrated working channel that allows passage of 5‐mm instruments down the same shaft. Operating scopes are available in two types: right angled or oblique (Figure 3.3). Some surgeons prefer this style of telescope for certain routine procedures such as biopsies, ovariectomies, and lately natural orifice translumenal endoscopic surgery (NOTES) because the instruments are always under visual control. For this reason, an operating telescope may also be recommended for novice endoscopic surgeons [1–5].
Figure 3.3 Operating laparoscopes. (A). Right angled. (B). Oblique.
Source: © KARL STORZ SE & Co. KG, Germany.
The viewing angle of a telescope is an important consideration because it affects both orientation and visual access (Figure 3.4). Standard forward‐viewing telescopes (0°) provide the simplest spatial orientation, centered on the axis of the telescope, but they present a relatively limited viewing field. A 30° distal tip angle allows the surgeon to view a larger area by simply rotating the shaft of the telescope on its longitudinal axis [8, 9]. With experience, the operator becomes proficient at using angled telescopes, thus gaining a wider viewing field. Telescopes with more acute tip angulations are also available (70, 90, and 120°), but they are rarely used in small animal laparoscopy and thoracoscopy [1–5].
Relatively new dynamic‐range rigid telescopes are available with a variable viewing angle, allowing the surgeon to control angulation from 0 to 120°, with a mechanical twisting mechanism near the eyepiece: ENDOCAMELEON – Karl Storz SE & Co. (Figure 3.5). These newer telescopes are currently used for selected procedures, mainly because of their versatile viewing abilities [10–12].
Figure 3.4 Telescope viewing angles. (A). 0°. (B). 30°.
Source: © KARL STORZ SE & Co. KG, Germany.
Figure 3.5 ENDOCAMELEON® telescope with variable viewing angle, adjusted by turning the collar on the eyepiece.
Source: © KARL STORZ SE & Co. KG, Germany.
These variable angle scopes are available in 4 and 10 mm diameter, for different size patients, the smaller size also being used for arthroscopy in humans. These newer scopes provide the surgeon with the ability to evaluate more thoroughly and maneuver the scope more easily, with an emphasis on thoracoscopic surgery. A recent study conducted at NCSU College of Veterinary Medicine demonstrated the advantages of the variable‐angle rigid scopes by providing an optimal alternative to circumvent the visual impediments of lung expansion during thoracoscopy when one‐lung ventilation is not feasible [10]. This study reveals that the use of an ENDOCAMELEON® significantly shortens exploratory thoracoscopic procedures, compared to the use of a standard fixed 30° angle telescope, while ventilating both lungs. The variable‐angle lens was also found to minimize iatrogenic injuries due to reduced maneuvering in the cavity compared to standard scopes [10–12].
Although fluorescence specific scopes exist (see next section on fluorescence imaging), the standard scopes can also be used, by adding a “snap‐on” dedicated filter between the ocular of the scope and the camera head lens, thus filtering the image to make visible the specific desired wavelengths. The subtracted light is eliminated from the picture, and a specific contrast obtained for the final image displayed on the screen. However, it is highly suggested for routine work with NIR that NIR‐dedicated scopes with integral filters be used since the snap‐on filters do not provide the same quality.
Using a telescope and instruments of the same diameter (i.e., 5 mm) is convenient for maximum flexibility during surgery and allows for exchanging location of the telescope and instruments during a procedure without exchanging ports [1–5, 9]. Nevertheless, trocar cannula can be fitted with a reducer to accommodate smaller diameter instrumentation without loss of pneumoperitoneum [9].
The development and adoption by surgeons of smaller diameter endoscopes has resulted in the detail provided by full HD miniature laparoscopy and the increasing trend toward needlescopy and associated instrumentation sets. That stated, miniature laparoscopy and needlescopy techniques make use of any rigid scope with a diameter equal to or smaller than 3.3 mm. The most common scope range used in clinical practice includes the 2.0, 2.4, 2.7, 3.0, and 3.3 mm. Therefore, the instrumentation varies from 2.0 to 3.5 mm. These scope lengths range from 14 to 25 cm allowing complete surgical access to deeper anatomic structures, even in medium‐sized patients.
Despite the wide range of smaller scopes available on the market, the most common