Exotic animal medicine can be tough! We often face problems that our domestic animal counterparts do not have to contend with, including diversity of species, general lack of pathognomonic clinical signs, limited serological tests and relatively few tried and tested therapeutic modalities. Notably frustrating are the reptile, avian, fish and small mammal cases. The inability to reach a definitive diagnosis can adversely affect the accuracy of prognoses and the effectiveness of chosen therapeutic interventions.
In 1994, I took an avian endoscopy training workshop at the North American Veterinary Conference, which changed the way I practised zoological medicine forever. During the last two decades, my research and clinical experiences across private practice and academia have only strengthened my belief that endoscopy is a diagnostic cornerstone of exotic companion animal practice, offering major benefits to general practitioners and specialists alike. This article is an attempt to convince those that do not use endoscopy to start – you will never look back!
Endoscopy is a diagnostic cornerstone of exotic companion animal practice, offering major benefits to general practitioners and specialists alike
The need for a definitive diagnosis
Our success in treating disease is largely dependent upon an accurate diagnosis, which also informs the client of the likely prognosis (often their primary concern). An accurate diagnosis dictates appropriate therapeutic approaches and removes the flawed guesswork associated with drug choices or whether surgery or medical treatment may be more pertinent.
It is still concerning that many exotic animal diagnoses are made merely to the organ level, with a presumed generic cause (eg parrots with respiratory disease, iguanas with renal disease, rabbits with cystitis, etc). What is really required is a definitive diagnosis to a histological and aetiological level. A definitive diagnosis relies on the demonstration of a patient’s pathological response and identification of the causative agent.
It is still concerning that many exotic animal diagnoses are made merely to the organ level, with a presumed generic cause […] What is really required is a definitive diagnosis to a histological and etiological level
Histopathology, cytology and serology
Essentially, a pathological response can be demonstrated through histopathology, cytology or paired rising serological titres. There are relatively few serological tests available for most exotic pets, and these often take several days to a week (or longer) to obtain results. The patient may well be better or dead by the time paired serology results are obtained, and consequently, they are typically used for retrospective confirmation. Cytology is the most rapid but suffers from a lack of tissue architecture; therefore, histopathology is usually considered the gold standard. Demonstration of the causative agent relies on microbiological culture, polymerase chain reaction (PCR), sensitive toxicological assays and a variety of other techniques for parasite identification.
It is well appreciated that the collection of samples from lesions/tissues for histopathology, microbiology, parasitology and/or toxicology remains the best hope of reaching a specific diagnosis. Samples can be easily collected post-mortem; however, diagnosis in the live animal requires an ante-mortem biopsy, and endoscopy offers a minimally invasive approach.
Diagnosis in the live animal requires an ante-mortem biopsy, and endoscopy offers a minimally invasive approach
To illustrate these points, let’s take a green iguana with suspected renal disease. An iguana suffering from anorexia and weight loss with a reversed calcium to phosphorus plasma biochemistry ratio most likely has renal disease; however, that is not a definitive diagnosis and does not indicate specific therapy. Radiology and ultrasonography may confirm renomegaly and, again, the likelihood of renal disease, but they still do not provide a definitive diagnosis. An iohexol excretion study can demonstrate decreased glomerular filtration rate and renal function, but although useful prognostically, it is still not a definitive diagnosis. Biopsy of the kidney with a histological demonstration of glomerulonephritis with calcification, interstitial nephritis and culture of Klebsiella bacteria with antimicrobial sensitivity testing is a definitive diagnosis from which more targeted and specific therapy can be prescribed.
The endoscopic solution
Ante-mortem biopsies can be collected via surgical excision, image-guided technology such as computed tomography (CT) and ultrasonography, or endosurgery. Unless part of the integument, surgical access to a lesion or diseased tissue typically requires an invasive approach which often involves extensive laparotomy/coeliotomy. CT- and ultrasound-guided biopsies are certainly possible, and techniques have been reported in exotic animal literature. However, iatrogenic trauma is more likely when compared to direct endoscopic visualisation (Ramiro et al., 1993).
There are also multiple examples in domestic and human literature to indicate the superior diagnostic value of biopsy histopathology over ultrasound-guided aspirate cytology (Roth, 2001; Falcone et al., 1993; Rawlings et al., 2003). Likewise, there are many examples of how endoscopy is less traumatic and less painful than traditional surgical approaches. In human medicine, faster recoveries, reduced hospital stays and decreased pain scores have been attributed to endoscopic procedures (Rau and Hunerbein, 2005; Parker et al., 2001; Yu et al., 1997).
The endoscopic approach is typically a non- to minimally invasive procedure, with the basic equipment required for the procedure outlined in Table 1.
| Equipment description | Primary indications |
| Endo-video camera and monitor Xenon light source and light guide cable Digital capture device | Required for all endoscopy procedures. Small all-in-one units have become very popular as they support both rigid and flexible endoscopy |
| 2.7mm x 18cm telescope, 30o oblique (wide angle) 4.8mm operating sheath | Stomatoscopy, otoscopy, rhinoscopy, tracheoscopy, gastroscopy, colonoscopy, cloacoscopy and coelioscopy in animals between 100g and 10kg |
| 1.7mm biopsy forceps 1.7mm single-action scissors 1.7mm remote injection needle 1.7mm grasping/retrieval forceps 1.7mm wire basket retrieval | Tissue biopsy Incising serosal surfaces to better access tissues for biopsy Aspiration of fluids from lesions or intra-lesional injection of drugs Removal of foreign bodies, parasites, etc Removal of larger irregular foreign bodies |
| CO2 insufflator with silicone tubing | Used for insufflation during reptile coelioscopy and mammal laparoscopy; not required for birds |
| Sterile saline suspended above endoscopy table with intravenous drip line to a port on the 4.8mm operating sheath | Used for sterile saline infusion for otoscopy, rhinoscopy, cystoscopy, cloacoscopy or small chelonian or fish coelioscopy |
Endoscopic evaluation of the gastrointestinal tract (via the mouth, anus or cloaca) and respiratory tract (via the glottis) require no surgical incision, yet the endoscopist can access deep internal structures (Figure 1). Endoscopy is a well-established standard-of-care diagnostic tool for investigating respiratory and gastrointestinal disease in dogs, cats and humans, so it should come as no surprise that the same applies to birds, reptiles, exotic mammals and fish (Sladakovic and Divers, 2021; Divers, 2010a, 2019a, b; Divers and Sladakovic, 2021).
Coelioscopy and laparoscopy
Coelioscopy and laparoscopy enable internal visceral evaluation and biopsy through a much smaller incision than required for a traditional coeliotomy/laparotomy (Figure 2). Indeed, once you start taking biopsies and comparing anatomical pathology to haematology and biochemistry results, you will develop a critical attitude towards the clinicopathology results that you previously relied on. As an example, a recent case series demonstrated that history, physical examination, diagnostic imaging, haematology and plasma biochemistry were poor compared to endoscopic biopsy for diagnosing hepatic disease in parrots (Hung et al., 2019).
Once you start taking biopsies and comparing anatomical pathology to haematology and biochemistry results, you will develop a critical attitude towards the clinicopathology results that you previously relied on
As mentioned, human and domestic animal medicine demonstrate the benefits of endoscopy and biopsy; however, an increasing number of studies and reports in exotic pet literature have also demonstrated the safety and effectiveness of these techniques in birds, reptiles, mammals and fish (Divers and Sladakovic, 2021; Divers, 2014; Divers et al., 2013; Mejia-Fava et al., 2013; Hernandez-Divers et al., 2004, 2007, 2009; Stahl et al., 2008; Hernandez-Divers, 2004). Once competency has been achieved, endoscopic techniques tend to percolate into other areas of veterinary practice. At the University of Georgia, we now routinely offer laparoscopic ovariectomy for rabbits and coelioscopic sex identification of juvenile turtles and tortoises (Divers and Sladakovic, 2021; Hernandez-Divers et al., 2009; Divers, 2010b).
Endosurgery
Once basic competency has been achieved using single-entry diagnostic procedures, evolution to endosurgery is the next step. In domestic mammals and humans, endosurgery is increasingly replacing more traditional surgical approaches. The documented improvements in reduced surgical morbidity and discomfort, alongside the more rapid return to normal behaviour and function, can also be enjoyed by our exotic animals.
Endosurgery has permitted enhanced surgical resolution of conditions where it is simply not possible using traditional techniques
Furthermore, endosurgery has permitted enhanced surgical resolution of conditions where it is simply not possible using traditional techniques. For example, surgical removal of cranial coelomic masses in birds has been attempted by the temporary removal of the keel but has invariably been unsuccessful. Endosurgical techniques permit access to the cranial coelom either cranially from the coelomic inlet or caudally from behind the last rib (Figure 3).
Another area that has seen significant growth in endosurgery is routine sterilisation and the treatment of reproductive diseases. Where I work, endoscopic ovariectomy is the routine sterilisation method of choice for young rabbits, large rodents, exotic carnivores, miniature pigs and primates (Figure 4). Furthermore, prefemoral endoscope-assisted techniques have greatly reduced the need for transplastron coeliotomies in tortoises and other chelonians (Figure 5).
Final thoughts
Diagnostic and/or surgical endoscopy is not an innate skill, and basic training is required. However, the learning curve is rapid (especially for diagnostic procedures), and clinicians can quickly become competent in the basic techniques. I can clearly recall the first endoscopy training course that I attended in 1994, where Dr Don Harris, the course leader, said, “you can’t be an avian veterinarian without endoscopy”. After 28 years, I can offer no argument against this position. Indeed, I would only expand on it by stating that “you can’t be an exotic animal veterinarian without endoscopy”. Given the size and delicate nature of many of the species we deal with, the continued development of endoscopic techniques in exotic animal medicine seems assured.
The author would like to state that their interest in endoscopy is solely clinical. They are not a paid consultant or employee of any endoscopy company, and all equipment used in their clinical service (Table 1) at the Veterinary Teaching Hospital, University of Georgia, has been purchased (not donated) through the generation of hospital income.
