Endoscopes: The equipment needed depends on the type of endoscopy and the body system to be investigated. Rigid and flexible endoscopes are available in a large assortment of sizes and lengths; both types have advantages and disadvantages (Box 13-2). Flexible endoscopes most often used in veterinary medicine are gastroduodenoscopes, bronchoscopes, and colonoscopes. Flexible scopes have a handle, an insertion tube, and an umbilical cord (Fig. 13-1). Bronchoscopes usually have a 2- to 6-mm outer diameter, gastroduodenoscopes a 7.9- to 10-mm outer diameter, and colonoscopes a 10- to 16-mm outer diameter. All scopes should have a biopsy-suction channel (usually 2 mm in diameter for bronchoscopes and 2- to 3.2-mm for gastroduodenoscopes and colonoscopes). Gastroduodenoscopes and colonoscopes have four-way deflection of the tip of the scope and an air-water channel that is used to insufflate air and wash off the viewing lens; bronchoscopes and ultrathin gastroduodenoscopes typically have only two-way deflection of the tip. Bronchoscopes do not have an air-water channel. The insertion tube typically has a working length of 40 to 60 cm in bronchoscopes, 100 to 135 cm in gastroduodenoscopes, and 130 to 220 cm in colonoscopes.

The ideal assortment of flexible scopes depends on the expertise of the operator and what procedures are anticipated. Ideally, a bronchoscope (4- to 5-mm diameter), a pediatric gastroduodenoscope (≤7.9-mm diameter with a 2-mm channel), and a regular gastroduodenoscope (8.5- to 9.8-mm diameter with a 2.8-mm channel) allow one to perform almost all procedures. Other flexible scopes that might be considered depending on one’s needs are a 1.6-meter pediatric colonoscope (helpful in extremely large animals and large, exotic cats) and an ultrathin bronchoscope or ureteroscope for small birds, pocket pets, and flexible cystoscopy or rhinoscopy. If you can purchase only two scopes, which will be used for both alimentary and respiratory tract work, consider a bronchoscope (4- to 5-mm diameter) and a gastroduodenoscope (8.5- to 9-mm outer diameter with a 2.8-mm channel). If you want only one scope and your clinic wishes to perform both respiratory and alimentary tract endoscopy, a 7.9-mm outer diameter pediatric gastroduodenoscope may be the best compromise. If you wish to obtain only one scope and it will be used only for alimentary tract endoscopy, an 8.5-mm outer diameter scope with a 2.8-mm channel is preferable.

Biopsy/cytology equipment: Biopsy and foreign body retrieval forceps for flexible scopes come in various shapes. The size of the forceps depends on the size of the biopsy aspiration channel; the larger the channel, the bigger and stronger the biopsy or retrieval device that can be used. If possible, a scope with a 2.8-mm channel should be used for most alimentary tract endoscopy in dogs and in cats weighing more than 3 to 4 kg. The tissue sample obtained through a 2.8-mm channel can be more than twice the size of a sample obtained through a 2-mm channel. These larger pieces of alimentary tissue can easily contain the full thickness of the mucosa and often some submucosa. The author (M.D.W.) prefers fenestrated biopsy forceps in an ellipsoid, alligator jaw configuration without a needle (Fig. 13-2); however, other endoscopists have other preferences that work for them. Disposable biopsy forceps are widely used in human medicine but seem to offer no real advantage in veterinary medicine.

Equipment used to obtain samples for cytology and culture typically consists of a stiff brush in a plastic tube. This brush is manually extended out the tip of the plastic tube once the tip of the brush assembly has been advanced through the endoscopic biopsy channel and is near the tissue to be sampled. However, such brush assemblies can be contaminated as they are passed through the endoscopic channel. Brush assemblies are made for when it is absolutely critical that a noncontaminated sample be obtained (i.e., culture). These brushes consist of an extendable brush that is within an extendable tube that is in yet another tube. The tip of the outermost tube is typically plugged so there is no chance of contamination when the scope is passed through the biopsy channel of the endoscope. Once the tip of the brush assembly is near the site to be cultured, the innermost tube is extended out the end of the outermost tube, and then the brush is extended out the tip of the innermost tube. Brushes for diagnostic purposes should never be cleaned and reused, as opposed to biopsy forceps, which can be used repeatedly.

Interventional tools for flexible endoscopes: A variety of special retrieval instruments are necessary to reliably remove most commonly encountered foreign objects. The most useful devices are a coin retrieval (W-type) forceps, a shark’s tooth forceps (especially useful for firmly grabbing cloth), an alligator jaw forceps, and a four- or six-wire basket (Fig. 13-3). The basket should be made of very flexible wire to facilitate passage over and around an object; however, this quality also makes it easier to bend the wire and ruin the basket. Other retrieval devices include wire snares, three-wire grabbers, magnetic-tip probes, and forceps with nonskid rubber; these instruments are seldom required.

Balloons and bougies have been designed to dilate esophageal strictures. Despite rhetoric that ballooning is superior to bougienage, success is more dependent on the skill and training of the operator than on the equipment used. Esophageal dilation balloons come in two major configurations: “over the wire” or “through the endoscope channel.” It is important to use these as opposed to a round balloon as is found on endotracheal tubes.

Other equipment includes sheathed needles that allow aspiration or intralesional injection of various lesions through the endoscope. A variety of flexible endoscopic biopsy instruments, snares, knives, and probes have electrocautery capability. Electrocautery snares are most commonly used because they allow removal of esophageal, gastric, and colonic polyps; they can also be used to make three or four quadrant “cuts” into esophageal strictures to aid in ballooning difficult lesions.