Veterinary Endoscopy for the Small Animal Practitioner. Группа авторов

Figure 2.30). Sheaths are designed with a round or oval configuration (Figure 2.36). Round sheaths are for penetrating structures when an airtight or watertight seal is required and are used for laparoscopy, thoracoscopy, percutaneous prepubic cystoscopy, and arthroscopy. Oval configurations are used when an airtight or watertight seal is not needed, and this shape allows space for a working channel within the sheath as is used for transurethral cystoscopy. Sheaths for cystoscopy, rhinoscopy, arthroscopy, vaginoscopy, or many of the “otheroscopies” use small telescopes and have sheaths that lock to the telescope. This locking mechanism is very important for protecting the lenses of small fragile telescopes and for function of the system in performing specific procedures. When locked in place, the distal tip of the telescope is aligned with the distal tip of the sheath which protects the distal lens of the telescope. More importantly, when the telescope is locked in place, the sheath protects against excessive bending stresses along the telescope shaft. This locking mechanism also creates a watertight seal at the proximal end of the sheath so that irrigating fluid flows through the sheath into the patient. It is very important that the telescope is properly locked in place for fluid flow, to prevent interference of the tip of the cannula with the visual field, and to prevent telescope damage.

Figure 2.35 (a) An assembled cystoscope for performing transurethral cystoscopy in large female dogs with the 4.0 mm cystoscope, a unidirectional flow sheath, and a connecting bridge with locking mechanisms to connect to the sheath and the telescope. Sheath diameters are available from 17 to 25 Fr with bridges that accept instruments from 5 to 12 Fr. (b) The disassembled components of the cystoscope system.

      (Source: Photo courtesy of Karl Storz: ©Karl Storz SE & Co KG, Germany.)

Figure 2.36 Round and oval sheaths for the 2.7 mm MPRT. The round sheath on the right is an arthroscopy sheath without a working channel. The oval sheath on the left is the cystoscopy or operating sheath with a working channel. The oval shape is required to create space for the working channel.

      (Source: Photo courtesy of Karl Storz: ©Karl Storz SE & Co KG, Germany.)

Figure 2.37 Locking mechanism designs for attaching sheaths to telescopes. From left to right: A snap in coupling mechanism with spring loaded locks, a traditional rotating ring locking mechanism, and an automatic lock.

      (Source: Photo courtesy of Karl Storz: ©Karl Storz SE & Co KG, Germany.)

Figure 2.38 A trocar‐cannula for laparoscopy. (a) An 11 mm diameter, 10.5 cm long laparoscopy trocar‐cannula with a sharp trocar in place, a single Luer insufflation connector with stopcock, an automatic valve, and a gasket to seal around 10 mm instruments. (b) A blunt trocar for use with the 11 mm diameter laparoscopy trocar‐cannula.

      (Source: Photo courtesy of Karl Storz: ©Karl Storz SE & Co KG, Germany.)

Figure 2.39 A 6 mm diameter, 10.5 cm long Ternamain Endo TIP cannula, with a single Luer insufflation connector with stopcock, a multifunctional valve, and a gasket to seal around 5 mm instruments. This cannula is placed by screwing the cannula through the abdominal wall tissue without a sharp trocar of blunt obturator.

      (Source: Photo courtesy of Karl Storz: ©Karl Storz SE & Co KG, Germany.)

Figure 2.40 A 3.9 mm diameter, 5.0 cm long lightweight trocar‐cannula with a Silicone leaflet valve. These small lightweight cannulas are only supplied with sharp trocars.

      (Source: Photo courtesy of Karl Storz: ©Karl Storz SE & Co KG, Germany.)

The locking mechanism of telescope sheaths has evolved over time from a rotating ring, to a sliding box (automatic), to a snap‐in design with spring‐loaded locks (Figure 2.37). The rotating ring is the traditional coupling mechanism being the oldest and simplest configuration for locking the telescope to the cannula. This design works well, has withstood the test of time for dependability, and is easy to use. The sliding box or automatic lock design is slightly easier to use, is more secure than the traditional coupling mechanism, but can become hard to slide over time eventually sticking and becoming inoperable. The snap‐in coupling is the most recent locking mechanism, is the easiest to use, and provides secure attachment of the telescope to the cannula.

Trocar‐cannulas for laparoscopy and thoracoscopy do not lock to the telescope but have a valve and gasket at their proximal end to prevent leakage of carbon dioxide during procedures (Figure 2.38). This trocar‐cannula is smooth and is inserted by pushing the sharp trocar through the abdominal wall or using a blunt obturator to pass the cannula through a preplaced incision or to replace the canula if it is dislodged or removed for any reason. Another trocar‐cannula design is a Ternamain Endo TIP cannula that is threaded and penetrates the abdominal wall by being screwed through the tissue (Figure 2.39). Trocar‐cannulas used for laparoscopy and thoracoscopy to establish operative portals are the same as the trocar‐cannulas used for the telescope portal. Trocar‐cannula sizes range from 2.5 mm diameter (Figure 2.40) to 13.5 mm diameter and lengths from 5 to 15 cm. The smaller cannula‐trocars are made of lightweight material