Telescopes and Sheaths

The 2.7-mm telescope system, first championed by Taylor, still remains the workhorse in exotic animal practice because of its versatility and ability to be expanded as individual practice caseload dictates.18–20 At time of press, a new 2.7 mm telescope with a significantly larger image size was released. The 2.7-mm Hopkins telescope can be used with a 3.5-mm protection sheath or with a 4.8-mm operating sheath that possesses ports for gas or fluid infusion and an operating channel for the introduction of 1.7-mm (5F) instruments (Figure 13-1). A smaller 1.9-mm telescope with an integrated sheath (3.2 mm) that can accommodate introduction of 1-mm (3F) instruments and a 1.0-mm semirigid (fiberoptic) miniature straight endoscope are particularly useful for small species (Figure 13-2).

Flexible Endoscopes

There are two main classifications of flexible endoscope: the fiberscope, which transmits the image via a bundle of fiberoptic fibers, and the video endoscope, which transmits the image electronically from a charge-coupled device (CCD) stationed at the distal tip. Fiberscopes are less expensive and are available in smaller diameters but have the disadvantages of pixilation and poorer image quality compared with video endoscopes (Figure 13-3). Video endoscopes tend to be larger in diameter because of the need to accommodate the terminal CCD chip, and their initial purchase costs have been considerably higher. Furthermore, until relatively recently, flexible and rigid endoscopy light sources and cameras were generally incompatible, which necessitated separate rigid and flexible tower systems. This undoubtedly forced practitioners to purchase one or the other. Fortunately, the advent of modern cameras and light sources now enables practitioners to invest in just one endoscopy tower that can be used with both rigid and flexible endoscopes.

Flexible endoscopes vary from 14 mm to less than 1 mm in diameter, and those greater than 2 mm often possess a working channel (for instruments) and tip deflection. Larger flexible scopes greater than about 7.8 mm often have four-way tip deflection, working channels, and air insufflation and suction (Figure 13-4). Current technology limits the smallest video endoscope to 3.8 mm although future improvements are expected; therefore smaller fiberscopes (0.5 to 2.5 mm) maybe more useful in small reptiles. However, these smaller fiberscopes often have just one-way or two-way tip deflection and smaller working channels (Figure 13-5).

Light Sources

The telescope is connected via a fiberoptic light guide cable to a light source (Figure 13-6, A). Halogen light sources are less expensive and are effective for small animals less than 2 kg, but xenon light sources provide better quality light and an intensity that can illuminate the body cavities of large animals. The hybrid xenon light source of the mobile Karl Storz Telepak is only 25 watts but has been used to perform coelioscopy in giant tortoises up to 100 kg.

Cameras

An endovideo camera connected to the eyepiece of the telescope, although once considered a luxury addition, is an integral part of the endoscopy system and greatly facilitates the surgeon’s performance (see Figure 13-6, A). Cameras, available in both European PAL and American NTSC formats, can vary dramatically in cost from budget single-chip cameras to three-chip digital high-definition (HD) models. The traditional video system provided a resolution of 720 × 480 pixels; therefore it inevitably led to some cropping of the image for display on a traditional 4:3 aspect monitor. The advent of HD systems has increased the video size to 1920 × 1080 pixels. In addition, the new 16:9 aspect ratio provides a 33% wider field of view while progressive (as opposed to interlaced) scanning produces improved resolution, color clarity, and refresh rates. Operating room setup is important: the monitor should be positioned directly in front of the endoscopist, and instruments should be within easy reach (Figure 13-6, B). In summary, the fact remains that any camera will greatly improve performance compared with just the use of an eyepiece and will also facilitate photodocumentation.

Rigid Endoscopy

The basic and most frequently used instruments include biopsy forceps, retrieval forceps, scissors, and needle (Figure 13-1, C). The 1.0-mm and 1.7-mm (3F and 5F) grasping forceps are useful for manipulating tissues, debriding, and retrieving foreign objects or parasites. The fine aspiration/injection needle can be used for the aspiration of fluid from cystic structures in cases in which biopsy may be contraindicated because of postsampling leakage. The needle can also be used for irrigation and drug administration. The 1.0-mm and 1.7-mm flexible biopsy forceps are used to harvest tissue samples for histopathologic and microbiologic analysis in patients as small as 30 g. The small sample size usually permits the collection of several biopsy samples for multiple laboratory tests and serial biopsies to monitor disease progression over time for assessment of a response to treatment. To take a tissue sample, the endoscopist inserts the biopsy forceps down the operating channel and into the field of view (Figure 13-12).

It is much easier to advance and manipulate the sheath–telescope–instrument as a single device than to try and keep the sheath–telescope still and independently move the biopsy forceps back and forth. With the biopsy forceps held open, the sheath–telescope–instrument is advanced to the tissue of interest, and when tissue enters the biopsy cup, the handle is released. These instruments are delicate, and the biopsy handle is often only required to open the biopsy jaws. The handle’s spring mechanism is usually sufficient to take a soft tissue biopsy sample without additional manual pressure, as long as the instrument is sharp. Clamping down on the handle will damage the forceps and increase biopsy crush artifact.

Some organs may be protected by a more fibrous membrane. The fixed blade of the scissors is inserted at a shallow angle through the membrane, and the sheath–telescope–scissors are advanced as a single unit, cutting the membrane as they proceed. The scissors can then be replaced by the biopsy forceps to take a sample through the capsular incision. Other instruments that can be invaluable in specific situations include a wire basket retrieval device (for removal of fibrous foreign bodies or stones; Figure 13-13), a polypectomy snare (for removal of small growths and polyps; Figure 13-14), and a radiosurgical needle electrode (for pinpoint ablation or coagulation).

Rigid Telescope and Instrument Handling

The fact that most pet reptiles weigh less than 2 kg requires careful control of the telescope; the eyepiece and camera should be supported with the superior hand, and the distal shaft of the telescope should be held by thumb and forefinger of the inferior hand (Figure 13-16, A). Handling the telescope in this fashion provides fine control without tremors; however, for a single surgeon to be able to use instruments, a modified hold is required. Inserting and manipulating instruments through the operating sheath requires changing from a two-handed to a one-handed technique. The usual thumb and forefinger support of the telescope shaft is now adjusted so that the inferior hand takes the entire weight of the sheath–telescope–camera system. The thumb is slid up the shaft of the sheath, and the fingers are curled over the top to encircle the sheath. Now that the sheath is grasped in a fistlike grip and the sheath is further supported by the thumb to prevent rotation, the superior hand can be removed to pick up and insert an instrument down the operating channel (Figure 13-16, B). This can only be performed with a correctly sheathed telescope; damage will occur otherwise.

Biopsy Care and Handling

It is interesting to note that various studies have concluded that endoscopic biopsy specimens are more diagnostic than ultrasound-guided aspirates or biopsy specimens.22–24 Endoscopic biopsy specimens are delicate and measure approximately 1 mm³ when collected with a 1.7-mm forceps. Handling and other histologic artifacts are reduced by gently dislodging the tissue from the biopsy cups into a small volume of sterile saline, then decanting into a biopsy cassette or bag, and submitting in 10% neutral buffered formalin (Figure 13-17, A).¹¹ Picking the biopsy specimen from the instrument with a needle will cause severe damage, and even moistened cotton-tipped applicators have been shown to cause tissue alteration (Figure 13-17, B, C). Biopsy samples for microbiologic analysis are best submitted in sterile saline for immediate processing. Alternatively, if mailed to a laboratory, they should be submitted in appropriate transport media. For the submission of samples for toxicologic or parasitologic analysis, it is wise to consult with the laboratory before sample collection.

Patient Selection, Evaluation, and Contraindications

Knowledge of species-specific anatomy, physiology, husbandry, and nutritional requirements are vital for properly evaluating the management and medical history of a reptile. Inexperienced clinicians are directed to reviews on the subject and should prepare ahead of time.25,26 Complete physical examination, including accurate body weight, is essential but may require sedation or anesthesia for aggressive snakes or uncooperative animals, particularly chelonians. Serial clinicopathologic data can be helpful in quantifying dehydration or indicating infection/inflammation, organ damage, or dysfunction. However, most published reference ranges are too broad to be of value unless patient data are severely abnormal. Complete blood counts and biochemistry panels (i.e., total levels of protein, albumin, globulin, aspartate transaminase, bile acids, glucose, creatinine phosphokinase, calcium, phosphorus, sodium, potassium, chloride, uric acid, ammonia, and urea for aquatic species) are recommended, and even in animals less than 100 g, hematocrit, a blood smear for differential white cell counts, and a total protein level can still be obtained.

Reptiles may be seen in a state of advanced, often chronic disease, and it is therefore important to stabilize patients before anesthesia and surgery. In addition to anesthetic complications, small patient size often presents the greatest challenges to the reptile endoscopist. The most common endoscopic procedures performed by the author include coelioscopy, gastroscopy, cloacoscopy, tracheobronchoscopy, and pulmonoscopy. However, most of the procedures described (or necessary modifications thereof) can be undertaken even in smaller reptiles, assuming equipment can be matched to patient size.

Obesity is less of an issue in chelonians and lizards because they store fat in discrete fat bodies rather than diffusely around organs like mammals. Obesity in snakes can still be a significant hindrance during coelioscopy.

Patient Preparation and Anesthesia

When reptile patients that are still feeding need to undergo an operation, fasting should be in accordance with body size and feeding strategy. For example, a 20-kg python would typically be fasted for 3 to 4 weeks, whereas a 50-g gecko would require only 1 to 2 days. Likewise, fasting a carnivorous turtle for 1 to 3 days would reduce the volume of food in the stomach, whereas fasting an herbivorous tortoise for the same period would have little effect, given that the majority of digesta is located within the large intestine. As a general guide, a single feeding cycle should be avoided before anesthesia and surgery.

Fluid therapy is the mainstay of stabilization, and hydration with crystalloids (with an osmolarity of 260 to 290 mOsm/L) at 25 to 45 mL/kg/day is recommended.²⁷ Fluids may be given intravenously or intraosseously for critical cases, or intracoelomically, subcutaneously, or orally. It is advisable to avoid oral or intracoelomic fluids immediately before gastroscopy or coelioscopy.

Certain examinations (e.g., stomatoscopy and cloacoscopy) may be possible in the conscious or sedated patient with the use of a mouth gag and appropriate restraint, but complete immobilization is preferred so that damage to equipment, patient, or staff is avoided. General anesthesia is recommended for all endoscopy procedures (including oral and cloacal examinations) and is required for any invasive procedures (including coelioscopy).9,28 Conscious coelioscopic examinations may be acceptable in research or wildlife under an appropriate experimental license, but in clinical practice, analgesia and anesthesia are considered mandatory. Some authors have reported using only local anesthesia for chelonian coelioscopy, but this likely provides inadequate analgesia for more involved coelioscopic procedures.²⁹ In a recent comparison of local versus general anesthesia for chelonian coelioscopy, anesthetic scores were significantly better for procedures conducted under general anesthesia compared with local lidocaine alone.⁹ A detailed description of anesthesia is beyond the scope of this chapter, but careful consideration should be given to intubation and adequate ventilation, especially when the coelom is insufflated during coelioscopy. There appear to be taxa-specific effects of opiates in reptiles given morphine (1.5 mg/kg) or hydromorphone (0.5 mg/kg): the dose seems effective in chelonians, whereas very high doses of morphine or butorphanol appear to be required for some lizards and snakes.^30,31 The nonsteroidal antiinflammatory analgesic meloxicam (0.2 mg/kg subcutaneously, intramuscularly, or intravenously) is used routinely in all species and may be repeated after 48 to 72 hours, if necessary.³²