Chapter 1
Endoscopy equipment

Valerie Walker

William R. Pritchard Veterinary Medical Teaching Hospital, University of California-Davis, Davis, California, USA

The endoscope is a medical instrument used for the visual examination of a body cavity or a hollow organ such as the lung, abdomen, ileum, colon, bladder, duodenum, nasal passages, or stomach. It is a rigid or flexible hollow tube fitted with a lens system and/or fiber-optic bundles to aid in the diagnosis and potential treatment of the patient. The function of the endoscope is to allow visualization of the mucosal surface to assess the degree of disease and allow tissue sampling for histopathology, culture, and cytology.

Endoscopy procedures have been a part of veterinary medicine since the 1970s. Today, these procedures are routinely performed in veterinary practices throughout the world. Types include bronchoscopy, esophagoscopy, gastroduodenoscopy, colonoscopy, nasopharyngoscopy, rhinoscopy, laparoscopy, and arthroscopy.

Endoscopes

Endoscopes are manufactured in a variety of sizes with different function capabilities, depending on the needs of the endoscopist. Endoscopes are divided into two groups: rigid and flexible. Both types of endoscopes start with the construction of a hollow tube. To drive light through the endoscope, thin fiber-optic filaments assembled into bundles are used to transmit light (non-coherent), and the image (coherent) to the distal tip. The different uses of fiber-optics in endoscopes include the way in which images are transmitted back to the endoscopist and the functional characteristics of the endoscope. While all-fiber-optic endoscopes use coherent fiber-optic bundles to transmit the image, video endoscopes use a video chip and rigid telescopes utilize a lens/rod system.

Rigid Endoscopes

Rigid endoscopes include sigmoidoscopes, pictured in Figure 1.1, and telescopes. The sigmoidoscope is used for visualization of the descending colon and rectum, and can be used in the esophagus to aid in the removal of foreign bodies. The sigmoidoscope is a hollow tube that can range from 10 to 19 mm in outer diameter (o.d.) with a length of 5-25 cm. When the viewing window is closed and the bulb insufflator engaged, a luminal view is obtained. Visualization is magnified through the lens of the viewing window and light is transmitted through fiber-optic bundles that encircle the inner recesses of the tube. Owing to the large inner diameter, multiple types of biopsy and retrieval forceps may be inserted when the viewing window is opened.

Figure 1.1 Sigmoidoscope with (from top) rigid biopsy forceps, large cotton tip applicators, sigmoidoscope with light handle and obturator. Inset: example of foreign body retrieved.

Telescopes are a higher quality medical-grade rigid endoscope. The hollow tube houses a series of glass rod lenses that magnify the image back to the eyepiece. The image is viewed on a monitor via an attached camera or with the naked eye. Light is transmitted from a remote light source through light cables that attach at the light guidepost. Fiber-optic light bundles pass through the insertion tube to the distal tip. Light cables may be steam sterilized for laparoscopy and cystoscopy, and most models can be immersed for disinfection (check with the manufacturer). Be sure that the light cables in your inventory attach securely to the telescope. Adapters are available for different models.

Rigid telescopes differ in outer diameters, viewing angles, and lengths, depending on their use (shown in Figure 1.2). These differences make them a versatile endoscope, especially when used in conjunction with an operating sheath. The o.d. can range from 1 to 10 mm, with lengths ranging from 18 to 30 cm. The most common telescope used in veterinary medicine is 2.7 mm by 18 cm with a 25 or 30° viewing lens.

Figure 1.2 Rigid telescope.

The viewing angle refers to the middle of the viewing field, shown in Figure 1.2. A 0° tip will allow for a frontward view, whereas an angled tip allows for an increased field of view by rotating the instrument. The angle of the tip can range from 10 to 120°.

Operating sheaths surround the rigid scope by attachment at the base of the eyepiece. Although the operating sheath will increase the outer diameter of the scope, it will also increase the telescope's versatility. Sheaths possess different functioning components. Fixed stopcocks positioned at the proximal end allow attachment for irrigation, or suction. Sheaths that have a working channel allow flexible instruments to pass beyond the telescope for biopsies and retrieval of foreign bodies. Levers on the stopcock control whether the port is opened or closed. When these features are utilized, the telescope becomes a multipurpose scope used to perform procedures such as cystoscopy, rhinoscopy, and arthroscopy.

Flexible Endoscopes

Flexible endoscopes are categorized into video and all-fiber-optic endoscopes. Fiber-optic endoscopes are commonly used in the veterinary setting since they are less expensive to operate, despite the fact they lack the superior technology of a video endoscope.

Video endoscopes offer greater image quality, resolution, and color. Incorporated in the distal tip behind the objective lens is a video chip that converts the image to a digital signal. This signal transmits through connection wires to the video processor. The image is sent to an image capturing device, monitor, printer, or computer.

Instead of a video chip, the all-fiber-optic fiberscope, seen in Figure 1.3, utilizes coherent fiber-optic bundles that transmit the image to the eyepiece. In order to view the image on a monitor, a camera must be attached at the eyepiece. Both types of endoscopes utilize non-coherent fiber-optic bundles to transmit light to the distal tip for illumination.

Figure 1.3 Basic flexible endoscope.

The fibers are as thin as a human hair and are pliable. They are arranged in a bundle inside the endoscope and can bend in response to the endoscope's movements. Once these fibers come into contact with moisture, they become hard and brittle and can break, resulting in either a loss of light (non-coherent) or a loss of image (coherent). As a result, all ports are sealed to protect the interior from water intrusion.

There are wide varieties of endoscopes available in today's market. The o.d. can range from 2.5 to 11 mm and greater, with insertion tube lengths varying from 55 to 240 cm. Other mechanisms that will vary are a two- or four-way tip deflection, insufflation, aspiration, irrigation, and the size of the operating channel. When selecting an endoscope, it is important to understand the needs of the procedure and versatility of the endoscope, plus the length and outer diameter of the insertion tube of each endoscope. A small 2.5 mm o.d. by 100 cm endoscope can be utilized as a male cystoscope and a bronchoscope for a cat or toy-breed dog. A 5.3 mm by 100 cm pediatric gastroscope can double as a small toy-breed gastroscope or a bronchoscope for a large-breed dog. For the cat or small- to medium-sized dog (10-15 kg), a 7.8 mm o.d. × 100-110 cm scope would be adequate for an upper gastrointestinal procedure. In some medium- to large-sized dogs, this would only allow visualization just past the pylorus. If the same scope was 140 cm long, the duodenum would be obtainable for viewing and a more thorough evaluation could be accomplished. Table 1.1 gives examples of flexible endoscope sizes and procedures. The procedural chapters review and discuss the best endoscope(s) for a given procedure.

Table 1.1 Examples of flexible endoscopes and their uses

An endoscope with four-way deflection, aspiration, and air/ water capability is essential for performing a gastrointestinal procedure. The degree of deflection should be 90 to 100 in a left and right direction with 180 to 210 deflections up and down. A bronchoscope may only...