Large Animal Endoscopy
Endoscopy has been widely employed in equine veterinary hospitals for many decades, particularly in the assessment of the upper respiratory tract of competition horses.
Its use is not restricted to this area, however. As the available range of endoscopes, tools, and accessories expands, so does the availability and application of endoscopy in large animal general practice.
Alongside its use in horses, the large animal endoscope may be a valuable tool for veterinarians working with production animals (particularly those of high economic value), camelids, farm pets, and zoological species.
Reasons to Perform Large Animal Endoscopy
As with small animals, large animal endoscopy may be undertaken for both diagnostic and therapeutic purposes. Cases benefiting from endoscopy may include those with the following:
Structural abnormalities such as strictures may be identified and possibly treated endoscopically
Conditions associated with exercise intolerance or poor athletic performance
Traumatic injuries, for example, bolusing injuries of the pharynx or esophagus in production animals, rectal tears in the horse post-examination
Ingestion or inhalation of foreign material which may be identified and retrieved endoscopically in most large animal species
Neoplastic disease visualization, biopsy, and, in some cases such as ethmoid hematomas, treatment
Parasitic disease identification and sampling
Infectious diseases such as guttural pouch mycosis or sinusitis in horses
Inflammatory disease for example Equine Asthma (EA) where bronchoalveolar lavage samples may be valuable
Gastric ulceration especially in horses
Large animal endoscopy may be used in the following organ systems:
Upper respiratory tract - including nasal passages, paranasal sinuses, guttural pouches, pharynx and larynx
Lower respiratory tract - including trachea and bronchi
Oral/dental assessment in all species
Upper gastrointestinal tract - including esophagus, stomach, and proximal small intestine
Lower gastrointestinal tract including the rectum and colon
Urinary tract
Reproductive tract
Large animal endoscopes
Large animal endoscopy most often employs a flexible endoscope (either a fiberscope or video endoscope) of diameter and length appropriate for the patient and organ system under investigation. Dynamic endoscopy is also now available, using a portable, wireless, flexible endoscope to assess an animal during exercise.
Large animal endoscopes require a light source, an air pump for insufflation, irrigation, and suction, as well as a monitor to receive the image in the case of video endoscopes. Fiberscopes and rigid endoscopes may be connected via a camera system to a display monitor.
Instrumentation for large animal endoscopy
Instruments used in large animal endoscopy may include the following, some of which are available either as single-use or reusable items:
Biopsy forceps – with various tips to suit the tissue to be biopsied. In this case, single-use forceps may be advantageous in gaining optimum biopsy quality as the cutting edge will always be sharp.
Grasping forceps – including rat-toothed, alligator jaws, or multi-pronged forceps
Retrievers, snares, or baskets – for the retrieval of foreign objects
Polypectomy snares – with cutting wire for the removal of polyps and other small growths
Cytology brushes – for collecting cell samples, particularly from the lower airway or gastrointestinal tract
Catheters with injection needles - for aspiration biopsy or flushing and aspirating fluid e.g. bronchoalveolar lavage
Guttural pouch probe – to help navigate the endoscope into the guttural pouch
Equine laryngeal forceps – particularly useful during trans-endoscopic laser surgery
Coagulation electrode – where hemostasis is required.
Other applications
Rigid endoscopes (or telescopes) are also widely used in large animal veterinary clinics. Applications may include
Dental assessment
Arthroscopy – for diagnosis and treatment (e.g. meniscal injury)
Thoracoscopy – for diagnosis and treatment (e.g. pleural lavage in pleuropneumonia cases)
Laparoscopy – for diagnostics (e.g. organ visualization and biopsy), elective surgery (e.g. cryptorchid castration or ovariectomy in horses) or therapeutic surgery (e.g. abomasopexy in cattle, neoplasia in all species, inguinal ring closure in equine hernia patients or nephrogenic space ablation after entrapment colic).
Artificial insemination and embryo transfer work
Theloresectoscopy – for diagnostics and minimally invasive teat surgery in cattle
Rigid endoscopes are passed through a trocar or cannula into the required space. Operating instruments for use during laparoscopy and thoracoscopy may include scissors, grasping forceps, biopsy forceps, injection cannulas, a palpation probe, needle holders, and knot tyers. Specialist instruments are available for embryo transfer in horses and cattle and for toggling procedures in cattle.
Instruments for use during arthroscopy may include probes to assess articular cartilage and subchondral bone; curettes for debridement; osteotomes and elevators for separating bone fragments; rongeurs; grasping forceps; arthroscopy punch for resection of cartilage, synovium or soft tissue masses; chisels; scissors; and drainage cannulas.
Conclusion
Large animal veterinary practitioners are presented with some specific challenges when diagnosing and treating our patients.
They are often, by definition, large in size which can limit the use of some diagnostic techniques such as abdominal radiography.
Frequently our patients would be at high risk under general anesthesia both in terms of risk to the patient and potential risk to the handler(s) too. In our livestock patients, in particular, financial limitations may preclude the use of advanced imaging modalities.
Large animal endoscopy represents an accessible, practical, and economically viable solution in many of these cases, both in terms of diagnostics and therapeutics.
Additional resources
The Veterinary Endoscopy Society - https://veterinaryendoscopysociety.org/
Equine endoscopy - https://adobevetcenter.com/equine-endoscopy/
Equine gastroscopy https://www.veterinary-practice.com/article/equine-gastroscopy-a-complete-perspective
Gastrointestinal biopsy in the horse https://journals.sagepub.com/doi/full/10.1177/10406387221085584
Transendoscopic URT laser surgery in the horse https://www.sciencedirect.com/science/article/pii/S0749073917302870
Livestock endoscopy - https://adobevetcenter.com/livestock-endoscopy/
Endoscopy in cattle https://pubmed.ncbi.nlm.nih.gov/22134601/#:~:text=Parts%20of%20the%20upper%20respiratory,prognosis%20of%20different%20pathological%20conditions.
Theloscopy in cattle https://www.sciencedirect.com/science/article/abs/pii/S0749072004000854?via%3Dihub
