Endoscopy Equipment and Terminology

Endoscopy is quickly becoming the standard of care for exotic animals as it offers a minimally invasive diagnostic and therapeutic tool to guide more specific and, therefore, effective treatments to patients. All too often, basic diagnostic workups (hematology, chemistry panel, survey radiographs) in avian, reptile, and small mammal patients fail to point to a definitive cause of an animal's clinical signs. Serologic tests are limited in these species, which makes antemortem diagnosis difficult without histopathology, cytology, culture, or other tests. Endoscopy, which allows the practitioner to literally see inside the animal, can become a useful internal physical examination to facilitate quick and safe tissue sample acquisition.^2,4 The ability of a veterinarian to obtain an antemortem diagnosis and base treatments off of a gold standard biopsy or culture, rather than nonspecific changes in physical exam and blood work, can have a significant effect on success of treatment case outcome, quality of life, and client/patient satisfaction.^4,6 Additionally, this information can be gained by use of naturally occurring orifices or minimally invasive "key-hole" incisions. The minimally invasive nature of endoscopy is hugely appealing to clients, due to the generally shorter anesthetic period, small incisions, quicker recovery, and minimal blood loss. Endoscopic equipment requires an initial financial investment, but clients are often willing to pay for an advanced diagnostic tool or a safer, less invasive alternative to traditional surgery. This specialty service can help set a practitioner or practice apart, which will lead to more referrals for the procedure.

Basic endoscopy equipment and diagnostic techniques are described below. More advanced techniques like endosurgery and multi-port entry are beyond the scope of this presentation and will not be discussed.

Equipment List for Basic Diagnostic Endoscopy in Exotic Pets

This list represents a basic setup, but certainly is not exhaustive. A practitioner can easily get started using endoscopy with only a selection of items listed here, but you need at minimum a telescope and light source.

 1.0-mm semirigid, 0°

 1.9-mm telescope, 30°

 For use with 1.0-mm biopsy and grasping forceps²

 2.7-mm telescope, 30°

 For use with 1.7-mm biopsy forceps, grasping forceps, remote injection needle, and 1.3-mm single-action scissors²

 Light source, ideally xenon and fiber optic light cable. Halogen light sources are suitable for smaller patients (< 2 kg)

 Video camera and monitor

 Ideally full-size monitor, but can also use hand-held monitors like Endogo® or adaptors for personal smartphones such as the Endoscope-i. The Tele Pack system combines a xenon light source, endovideo camera and monitor into one portable unit.

 CO₂ insufflator with tubing

 For small mammal laparoscopy and reptile coelioscopy

 Sterile saline and IV tubing

 For reptile or fish coelioscopy, cloacoscopy, cystoscopy, rhinoscopy, otoscopy

Operating Room Setup and Equipment Maintenance

It is advised to have most or all endoscopy equipment including a monitor and light source set up on a designated cart that can be transported to various areas of a hospital. This allows use of endoscopy equipment in exam rooms, procedure areas, as well as the operating room. If redundancy of equipment is available, one set of instruments and telescopes should be kept sterile, while another set left clean and available for quick, non-sterile exams or procedures. However, in most cases this is not an option and equipment will need to be cleaned and sterilized between each use. If the equipment is kept sterile, do not hesitate to open it and use it for non-sterile purposes. All too often, this equipment is obtained with the best intentions to use it frequently and develop skill. However, there is frequent hesitation to open a sterile pack for brief (non-sterile) use. If this is the case, keep the equipment clean, but not sterile. If a time-sensitive need arises for sterile equipment, the use of "cold sterilization" techniques is acceptable.

Positioning of equipment and patient is dependent on the procedure being performed. However, it is generally recommended that the monitor be positioned directly in front of or across from the endoscopist. This will allow the best visualization without causing the endoscopist to have to turn their head or otherwise change their body position during the procedure. When holding the telescope and camera, the dominant hand is positioned to support the camera and "drive" the telescope. The non-dominant hand holds the distal end of the telescope between the thumb and index or middle finger. This helps to stabilize the end of the telescope and prevent inadvertent advancement of the telescope, which could cause tissue trauma. The endoscopist should make every effort to remain in a neutral position with straight neck and relaxed shoulders. Once the initial entry is established, subsequent maneuvers should be directed by the images on the monitor, not by looking at the patient and telescope itself. To avoid tissue trauma and aid visualization, always move the telescope into areas of "open space."

Avian Endoscopy

The major limiting factor in avian endoscopy is the small size of some species, particularly when one is just learning to become proficient in endoscopy. Species differences can make entry and visualization more difficult, and any bird with free fluid in the coelom should not have lateral (left or right approach) coelioscopy performed, as the communication established with the air sac system can cause the bird to drown.

Tracheoscopy

Birds undergoing tracheoscopy will need to be under general anesthesia and positioned in dorsal or ventral recumbency. Anesthesia should be maintained using an air sac cannula, which leaves the upper airway clear for endoscopy. The size of the patient will dictate the size of telescope used. If tracheal diameter dictates that the available telescope needs to be used without the operating sheath, care must be taken to prevent damage to the telescope. Biopsy forceps and other instruments can still be used alongside the telescope, or within operating channels.

Cloacoscopy

The cloaca, including the coprodeum, urodeum, and proctodeum, can be examined using warm saline to aid distension and visualization. Birds should be under general anesthesia and intubated. If excessive fluid is used to distend the cloaca, oral regurgitation can occasionally be observed.

Coelioscopy

Previous clinical workup should dictate which approach(es) are indicated for a given patient based on target tissues to examine or sample. The left lateral approach is the default and is the best approach to visualize the spleen. The right lateral approach is used to evaluate the pancreas, and the ventral approach is used if both lobes of the liver need to be examined or sampled, or if the bird has free fluid as this approach does not enter through the air sacs. Insufflation is not needed due to the presence of the air sac system.

Left lateral entry to the coelom is performed as follows: Position the bird in right lateral recumbency with left leg pulled forward and secured (typically vet wrap is used to tie foot to neck). Locate the last rib, the pelvis, and the flexor cruris medialis muscle (FCM). A few feathers may need to be plucked to clear the entry site. Strips of tape can be used to secure feathers out of the field. Aseptic preparation of the patient and sterile draping follow. The use of clear adhesive drapes is helpful to keep feathers out of the field while allowing visual assessment and monitoring of the patient under anesthesia. The intersection of the last rib and the FCM muscle forms the incision site. A #15 blade is used to create a 2–4-mm skin incision, after which straight hemostats are used to bluntly dissect the soft tissues, and advanced (jaws closed) in a slightly cranial direction to "pop" into the (left) caudal thoracic air sac. It is important to exercise control during this step, and it is recommended to hold the hemostats along the mid-shaft so as to not inadvertently advance them too far. Once the left caudal thoracic air sac has been entered, the hemostat jaws are gently opened as retracted in order to establish a defined opening for the telescope.¹ The telescope is introduced and oriented, with the cranial thoracic air sac to the left, abdominal air sac to the right, lung straight ahead, liver and proventriculus ventral. In order to enter the cranial thoracic and abdominal air sacs, the tip of the endoscope is used to create an opening in the associated air sac membranes. These membranes are normally thin and transparent and allow visualization of viscera on the other side. In some disease states the membranes can become thick, irregular, and opaque. Care should be exercised when penetrating these air sacs as more force may be needed, coupled with poor visualization of viscera on the other side.

Organs Seen in Each Air Sac

Cranial thoracic air sac: lung, liver, heart, great vessels, caudal esophagus.¹ Caudal thoracic air sac: liver, lung, proventriculus.¹ Abdominal air sac: kidney, gonad, adrenal gland, external iliac vein, ureter, spleen (left side), small intestines, duodenum, colon, cloaca, ceca, pancreas (right side).¹

Biopsy Acquisition

The liver is most easily accessed through the caudal thoracic air sac. The hepatoperitoneal membrane covers the surface of the liver and needs to be cut to allow access to the parenchyma (to avoid crush artifact if biopsied through the membrane). Endoscopic scissors are first advanced through the operation channel until the blades are visualized. The blades should be opened and visualized, and then the telescope and scissors are advanced together as one unit to cut the membrane. Do not advance the scissors independent of the telescope. The kidney is accessed through the abdominal air sac and does not have an overlying membrane. To biopsy the liver (once the hepatoperitoneal membrane has been cut) and kidney, introduce the biopsy forceps through the operating channel until their jaws are visualized. Open the jaws and orient the forceps to the plane of tissue to be sampled. Advance the biopsy forceps and the telescope as one unit into the tissue and close the jaws. The forceps are pulled away from the tissue in a swift motion and removed from the operating channel. A sterile needle can be used to help remove the tissue from the forceps jaws into a biopsy cassette, or the forceps can be swirled in sterile saline to help remove the tissue. It is recommended to obtain multiple biopsy specimens from each tissue to allow submission for histopathology, culture, and other testing. Bleeding is usually minimal, and biopsy sites should be visualized to assess that clotting has occurred.

Closure is simple and involves a single interrupted or cruciate suture in the muscle and a single suture in the skin. Absorbable suture is recommended. The most common complication is mild subcutaneous emphysema if an inadequate seal is achieved. This is usually clinically insignificant and resolves over a few days.

Reptile Endoscopy

Tracheoscopy

Reptiles typically tolerate tracheoscopy and partial or complete obstruction of the trachea for short periods of time. Therefore, an alternative airway is not necessary as it is in birds. Tracheoscopy is easily accomplished in snakes, lizards, and large chelonians. However small chelonians may require pulmonoscopy (through the carapace) to examine the airway.

Cloacoscopy

Cloacoscopy in reptiles is accomplished similarly to birds. Warm saline is used to aid distension and visualization. In species with a urinary bladder, the telescope may be introduced through the urethra for visualization and retrieval of uroliths.

Coelioscopy

Coelioscopy point of entry varies in reptiles by species, body conformation, size, and target organs. Major applications are examination of viscera, tissue biopsy or sample collection, and often oophorectomy in females. Insufflation can be accomplished with CO₂ or saline, depending on species, and the pressure recommended (3–5 mm Hg) is lower than in mammals (8–14 mm Hg).⁵

Small Mammal Endoscopy

Intubation

Rabbits and rodents have narrow oral cavities that are difficult to access for examination and intubation. An endoscope can be used in place of a laryngoscope to aid direct visualization of the glottis and allow swift intubation with the largest endotracheal tube permissible by patient size. Blind intubation, though reliable when practiced, does not allow visualization and assessment of trachea size. Therefore, endoscope-assisted intubation often allows successful intubation with larger sized endotracheal tubes than would otherwise be placed using the blind technique.³ Endoscope-assisted intubation can be performed by placing the endotracheal tube over the telescope, or by passing the endotracheal tube alongside the endoscope. The use of either technique is acceptable and will be dictated by user preference, patient size, and size of telescope available (i.e., if a patient is small requiring intubation with a 2.0-ET tube, then a 1.0-mm telescope will be required for over-the-endoscope technique; if only a 1.9- or 2.7-mm telescope is available, then the side-by-side method should be used).³

Stomatoscopy

Anesthetized endoscope-assisted oral examination aids in more thorough dental assessments and can guide dental trimming/extraction, abscess debridement, and intubation.Intubation during dental procedures is ideal, but if the size of the oral cavity precludes the use of endotracheal tubes in conjunction with dental instruments and the telescope, then anesthesia can be maintained by nasal intubation or small facemask.

Rhinoscopy

Upper respiratory infections are common in rabbits and rodents. Culture of nasal discharge often grows a mixed population reflecting secondary pathogens and/or contaminants. However, rhinoscopy allows visualization of abscesses, granulomas, foreign bodies, etc. Debridement, sample acquisition, and local treatment of lesions are also facilitated by use of endoscopy. Patient size will dictate the size of telescope used. Large rabbits may permit use of a 2.7-mm telescope with or without the operating sheath. As patient size decreases, the 1.9- and 1.0-mm telescopes may be used; however, no operating sheath can be used with the 1.0-mm telescope. Whenever a telescope is used without the sheath, care must be taken to prevent bending and damage. Additionally, any instrument or nasal flushing would need to occur alongside the telescope. Rabbits anesthetized for rhinoscopy should be intubated.

Gastroscopy

Gastroscopy in small mammals is most commonly performed in ferrets. The use of small flexible endoscopes provides the ability to visualize lesions (e.g., ulcers, masses) and collect samples for culture and histopathology, which should be considered routine and standard of care.³ The stomach of small herbivores is rarely empty, which makes gastroscopy in these species extremely difficult.³

References

1.  Divers SJ. Avian diagnostic endoscopy. Vet Clin North Am Exot Anim Pract. 2010;13:187–202.

2.  Divers SJ. Endoscopy equipment and instrumentation. Vet Clin North Am Exot Anim Pract. 2010;13:171–185.

3.  Divers SJ. Exotic mammal diagnostic endoscopy and endosurgery. Vet Clin North Am Exot Anim Pract. 2010;13:255–272.

4.  Divers SJ. Making the difference in exotic animal practice: the value of endoscopy. Vet Clin North Am Exot Anim Pract. 2015;5:40–47.

5.  Divers SJ. Reptile diagnostic endoscopy and endosurgery. Vet Clin North Am Exot Anim Pract. 2010;13:217–242.

6.  Hernandez-Divers S. Modern endoscopy equipment and advanced endoscopy techniques in birds and reptiles. Exotic DVM. 2003;5:61–63.