Upper Respiratory Tract Endoscopy in the Cat

Abstract

Clinical challenges:

Endoscopy of the feline upper respiratory tract has always taken a bit of a back seat to exploration of the canine nose and paranasal sinuses, pharynx and trachea, due to some anatomic limitations and lack of availability of appropriate-sized equipment.

Practical relevance:

With proper training, however, even the inexperienced endoscopist can find that endoscopy and endoscopic surgery can be of tremendous utility in feline practice. What had previously been largely off-limits sites, in terms of direct visualization and surgical intervention, the feline rhinarium, paranasal sinuses, pharynx and trachea are now anatomic areas that can be effectively visualized in most clinical scenarios. Moreover, endoscopic surgery is now an area gaining significant appreciation for its diagnostic and therapeutic benefits.

Audience:

This article will not serve as a complete treatise on disease processes of the upper respiratory tract in cats, but rather is intended as a technical and instructional reference point on upper airway endoscopy for veterinary surgeons, both in first opinion as well as referral small animal practice.

Clinical indications and patient presentation

Cats in need of evaluation of the upper respiratory tract present in various ways, but there are multiple commonalities that should signal to the clinician the potential utility of using endoscopy in diagnosis and also intervention.

Compared with canine practice, where the coughing dog is often the most common clinical presentation, cats often present with more subtle signs of respiratory distress. Often the first signs of nasal or paranasal disease are nasal discharge and sneezing. Depending on the particular case and the particular pathology, the discharge may be unilateral or bilateral and careful note should be made of this as well as whether one nostril seems to have more substantial discharge compared with the other. The discharge may range from mucoid to mucopurulent, to serous, to hemorrhagic, or any combination of these, with a wide overlap in visual appearance between the various forms. Epiphora or discharge at the nasolacrimal puncta may also be present, either primarily or in concert with discharge at the nares. Acute or chronic epistaxis should always alert the clinician to the potential for primary nasal disease. The color and odor of the discharge is of particular importance to note.

Owners may also report subtle signs of dyspnea, which in the cat can often be evident as a slight increase in the abdominal component of respiration. This is an important observation in assisting the clinician in localizing the disease pattern to the lower or upper respiratory tract.

Coughing, gagging or retching, which some owners may misinterpret as vomiting if productive, should alert the clinician to the suspicion of pharyngeal or laryngeal disease. Careful examination and appropriate diagnostics should differentiate pulmonary or cardiac causes of coughing from upper respiratory disease.

Clients may also note audible wheezing, and stertor should be differentiated from stridor on physical examination. Often owners will offer that their cat seems to be a ‘noisy sleeper’, as the subtle sounds of stertorous breathing may only be evident in the quiet of sleep. Careful anamnesis, physical examination and observation of the patient can aid the clinician in differentiating the genesis of these auditory signs. Stertor is usually heard as a low-pitched snoring or snuffling sound. This is most commonly caused by turbulent air flow across the mucosal surfaces of the pharynx, nasopharynx and/or soft palate. Stridor, by comparison, is of lower respiratory tract origin within the larynx, trachea or proximal portions of the main stem bronchi.

Changes in appetite are a subtle but important sign of nasal disease. As cats are so much more attuned to the odor of their food, any pathology that interferes with their ability to smell may impact appetite, and weight loss and anorexia may ensue. The cat that seems interested in food, sniffs at the food dish and then walks away should undergo careful examination of the nose to ensure that an anatomic obstruction to olfaction is not present. Additionally, cats that seem to have difficulty in prehending or swallowing may well have anatomic lesions affecting the pharynx, nasopharynx or posterior nares that can interfere with these activities. A cat that extends its neck while eating in an attempt to aid in the passage of food may have pharyngeal pathology. Pain may be evident on mastication or swallowing that is accompanied by this cervical extension.

Less commonly, owners may appreciate facial swellings or facial asymmetry that may suggest nasal pathology.

Physical examination and anamnesis

During the examination, a careful and thorough history should be obtained, paying special attention to the cat’s age at onset, and duration (chronic vs intermittent) and seasonality of the clinical problem. Attention to the cat’s body condition and weight is also important, and a careful assessment as to the trend in the same should be made. Discussion with the owner as to the cat’s appetite and whether there are certain foodstuffs that are more enticing to the cat (ie, more aromatic, and/or when warmed to slightly above room temperature) or easier to prehend and swallow is important. As mentioned, owners may often comment that there has been a change in the sound of the cat’s breathing pattern, and may particularly notice this at night.

Physical examination that focuses on the upper respiratory tract should be comprehensive (see box below), although there are clear limitations to what can be achieved in the conscious feline patient.

Diagnostic investigation

Once the client consultation and initial physical examination have been undertaken the remainder of the diagnostic investigation is best completed under general anesthesia. Depending on the particulars of the case in hand, a complete blood count (including platelets) and biochemistry profile should be performed as part of a minimum database. Interpretation of results should attempt to identify co-morbidity that might affect the patient’s safety under general anesthesia, as well as other pathologies that might be clinically relevant. If epistaxis is part of the clinical presentation a coagulation panel should be evaluated. As epistaxis can also be associated with hypertension blood pressure measurement should be performed. If so indicated, other causes of hypertension should be ruled out prior to general anesthesia.

With the patient under anesthesia, a complete and detailed oral examination should be conducted, including direct visual examination of the pharynx and larynx. Dental examination, including assessment of periodontal pocketing, should be performed with an eye towards identifying dental pathology that might have oronasal implications. Assessment for the presence of mass lesions dorsal to the soft palate should be made by visualization and palpation.

Survey radiographs are helpful and an important part of the work-up, but are often not definitive in describing the pathology. Radiographic views should include the lateral projection, ventrodorsal view (Figure 1a) and frontal sinus skyline views (Figure 1b). High quality digital dental radiography, if available, provides a degree of resolution that is very valuable in dental radiography, as well as imaging of the rhinarium; in particular, bisecting angle views of the upper canine teeth are often of significant diagnostic value. Digital radiography has made the use of standard radiographic equipment of much greater value in examinations of the head and rhinarium.

Figure 1.

Radiographs showing a nasal and frontal sinus mass, which was subsequently diagnosed as a lymphosarcoma. (a) Open mouth ventrodorsal view. (b) Frontal sinus skyline view. Images courtesy of Middlesex County Animal Hospital, MA, USA

It is worth noting, although somewhat outwith the scope of this article, the utility of both magnetic resonance (MR) and computed tomography (CT) imaging. These modalities provide excellent resolution and definition of pathology of the rhinarium and paranasal sinuses. One distinct advantage of these technologies is their ability to clearly define soft tissue lesions. While referral centres (both academic and private practice) increasingly have access to these scanners, they are still not readily and widely available in many areas. When feasible, however, owners should be offered access to these imaging modalities. In an ideal scenario, one would be able to perform either CT or MR imaging during the same anesthetic procedure as the endoscopy. Often though this is not practicable and the procedure may need to be staged.

Imaging notwithstanding, there is still no substitute for histopathology as the gold standard for definitive diagnosis.

Functional anatomy pertinent to rhinoscopy, pharyngoscopy and tracheoscopy

The cat has essentially the same nasal and pharyngeal anatomy as the dog, albeit in a more compressed and smaller space (Figure 2). This has clinical implications in terms of equipment choices (see boxes on pages 1010–1011) and endoscopic approaches.

Figure 2.

Nasal and pharyngeal anatomy in the cat. (a) Lateral view of the skull. (b) Diagram of a sagittal section through the skull to demonstrate the turbinate bones. (c) Rostral view of the skull. (d) Diagram of a transverse section through the skull at the level of the canine tooth. Adapted from Reed and Gunn Moore (2012) ¹

The rhinarium itself is divided into three primary open spaces or meati: the dorsal nasal meatus, the ventral nasal meatus and the middle nasal meatus. Anatomically these are bounded by the dorsal, ventral and ethmoidal nasal conchae. Within the dorsal nasal meatus are the dorsal nasal and ethmoidal turbinates. The most clinically sensitive structure in the dorsal nasal meatus is the cribiform plate. This bony wall separates the rhinarium from the calvarium and brain case, and contains the nerves communicating olfactory sensation from their receptors on the ethmoid turbinates. The cribiform plate is highly vascular and pathology associated with this structure often has epistaxis as a salient clinical feature. This has important implications for endoscopic therapy (see later).

The dorsal nasal meatus is bounded, as mentioned, by the dorsal nasal concha laterally and the ethmoid concha ventrally. The ventral nasal meatus communicates with the pharynx via the posterior nares. The opening of the Eustachian tube can be visualized in some feline patients as a thin slit on the lateral wall of the nasopharynx caudal to the choanae.

The most problematic feature of the anatomy of the feline patient is the relatively compressed space that the dorsal and ventral nasal meati occupy. This limits equipment choices (see later). It can also make differentiating the ventral from dorsal meatus, as well as visualization of other anatomic landmarks, difficult as these structures are often in such close proximity that identifying them as discrete structures can be confusing, particularly for the practitioner not well experienced in endoscopic techniques.

The nasal planum and nares are also quite tricky to manipulate, compared with the dog. The nares are much narrower than their canine counterparts. The entry to the rhinarium and dorsal nasal meatus is essentially parallel to the long axis of the nose (distinct from the dog where a slight ventral approach is necessary to introduce the endoscope safely into the dorsal nasal meatus, and subsequently into the ventral meatus). This means that the path of least resistance in the cat is entry into the dorsal nasal meatus. As discussed below, entry into, and identification of, the ventral nasal meatus is more difficult than in the dog.

Figure 3.

A selection of rigid and flexible rhinoscopes commonly employed in feline practice: (a) 2.7 mm 30° rigid scope; (b) 1.9 mm 30° rigid scope; (c) 3.7 mm two-way deflection flexible endoscope. ©2013 Courtesy of KARL STORZ GmbH & Co KG

The anatomy of the frontal sinuses is essentially the same, except for the obvious differences in size between the species. The communication of the frontal sinuses with the rhinarium is difficult to visualize and even more difficult to traverse endoscopically, except in the most pathologic of states.

The larynx of the cat is similar in structure to that of the dog and, as such, tracheoscopic examination is similar. However, the tendency of the cat towards laryngospasm should the arytenoids be manipulated too aggressively should be kept in mind. The diameter of the lumen of the trachea has important implications with regard to equipment and procedural choices.

Rigid antegrade rhinoscopy

Preparation of patient and equipment

Once the decision has been made to perform an endoscopic intervention of the upper airways anesthesia considerations are determined by the specific clinical case at hand and any significant co-morbidity that the pre-anesthetic investigation has uncovered. The use of inhalant anesthetic gas delivered by endotracheal tube is generally considered the standard of care (continuous rate infusion of propofol can also be considered).

As rhinoscopy often involves the copious use of irrigant fluids, protection of the airway is of vital importance to minimize the risk of aspiration pneumonia, which is one of the primary potential complications of feline rhinoscopy (see left).

Figure 4.

(a) 2.7 mm 30° rigid telescope, (b) protective sheath for telescope, (c) multipurpose cannula for telescope, (d) grasping forceps and (e) biopsy forceps. ©2013 Courtesy of KARL STORZ GmbH & Co KG

While the patient is being prepared for and induced under general anesthesia, the endoscopist should be readying their surgical space and equipment set-up.

Equipment should be thoroughly sterilized as per manufacturers’ instructions. Sterile irrigation solution should be hung on an intravenous pole near the head of the patient. The author usually uses 0.9% saline in 1 l bags for this purpose, attached to a standard intravenous or giving set. However, any clear additive-free physiologic solution can be used (lactated Ringer’s solution, Normosol, etc, all without added dextrose).

Given the mess that can be created with the use of aggressive irrigation, performing the procedure on a ‘wet table’ is of great utility. This will help keep the operatory cleaner and, if nothing else, will make the nurses much happier with the reduced clean up.

With the patient under general anesthesia and intubated, preparation for the procedure can begin. The author usually starts with the cat positioned in sternal recumbency. The head is propped up with soft towels (Figure 5a) to elevate the rhinarium to allow for access. However, care should be taken to avoid tipping the nasal planum too far dorsally; overextension of the cervical spine in this manner will increase the risk of aspiration of irrigation solution. The author usually tries to have the head elevated with a slight downward deflection of the nasal planum.

Figure 5.

Theatre set-up for a mobile endoscopy practitioner, demonstrating patient positioning in sternal recumbency (a) as well as positioning of monitor, camera and light source level with the patient’s pelvis (b). Images courtesy of Middlesex County Animal Hospital, MA, USA

The endoscopic equipment tower is generally placed at the level of the patient’s pelvis facing forward (Figure 5b). This allows the operator to sit at the patient’s head and be presented with a more or less true orientation of image on the video monitor. A surgical stand with equipment and disposable supplies is generally placed at the level of the surgeon’s shoulder on the same side as the tower, although this is subject to individual preference. The anesthesia machine is carefully positioned on the opposite side of the equipment tower. A mouth gag or dental speculum is placed to keep the mouth open. A maxillary mouth gag provides a measure of safety to ensure that the jaw is not held under excessive tension for a long period of time, risking the rare complication of central blindness.

Pharyngoscopy

The first procedure of the work-up is retroflexed or ‘J’ maneuver pharyngoscopy. With the cat’s mouth open, the flexible endoscope is manipulated so that the operative or bending end is flexed into a hook or ‘J’ position. The endoscope is advanced into the mouth and the scope hooked over the soft palate so that the optical end of the endoscope is facing rostrally. Bearing in mind that the view on the video monitor is reversed and inverted, this allows for examination of the posterior nares.

Any mass or structural lesions noted to be obscuring the openings of the posterior nares (Figures 6 and 7) can be biopsied or aspirated. If a mass such as a nasopharyngeal polyp is observed, and can be retracted caudally over the edge of the soft palate with the aid of an endoscopic grasping forceps, a diode laser or some other form of thermal energy can be used to transect the stalk directly. Alternatively, for more rostral lesions that cannot be manually manipulated, small diameter diode laser fibers can be introduced through the instrument channel to ablate the tissue. Effusions noted at the posterior nares can be retrieved for cytologic analysis via brushes or aspiration cannulae. The operator should be aware that while many two-way deflecting endoscopes allow for bending beyond 180°, the presence of any instrument in the channel through the bending portion of the endoscope will decrease the maximum range of the endoscope. Forcing the endoscope beyond the point of resistance runs the risk of damaging the wires of the bending end of the instrument.

Figure 6.

Retroflexed ‘J’ maneuver endoscopic image of the caudal nares and choanae, demonstrating nasal lymphosarcoma presenting as a nodular mass lesion

Figure 7.

Nasal lymphosarcoma can present in a variety of gross appearances. Here nasal lymphoma is a pale space-occupying mass in the dorsal nasal meatus

With the flexible endoscope still in the pharynx the flexion can be relaxed to give the operator a very good 360° visualization of the entire pharynx, including both the dorsal and ventral surfaces of the hard and soft palates, the roof of the pharynx, tonsillar crypts and the larynx itself.

Rostral rhinoscopy

With that portion of the procedure completed, the mouth speculum can be removed and rostral rhinoscopy performed with the rigid endoscope of the operator’s choice. The author usually assembles the endoscope, light guide cable and camera in such a way that he can hold it pistol-style; that is, so that the light guide post of the endoscope, the light guide cable and the cable of the camera all drape in such a manner as to keep the camera orientated in an upright position. This ensures that the image produced by the camera is in the same orientation as that of the endoscope. The result is a true (rather than inverted) image on the monitor.

With the non-endoscope-holding hand, the surgeon gently displaces the nasal planum dorsally and gently inserts the well lubricated endoscope through the nares (Figure 8). As noted earlier, the scope will by default enter the dorsal nasal meatus. Once the endoscope is inside the nose, the irrigation can be turned on via gravity feed (usually no pump is necessary, although the occasional blast of saline via a syringe can help free the operative field of tenacious mucoid debris). The minimum amount of irrigant flow is used to keep the operative field clear. Small hand movements translate to dramatic motion of the tip of the endoscope in such a small location. So care must be taken to make advancements, retractions and lateral motions of the endoscope incremental and slow. While some degree of hemorrhage is unavoidable in rhinoscopy, a delicate approach will minimize iatrogenic trauma.

Figure 8.

Rostral rigid rhinoscopy. The surgeon can be seen deflecting the nasal planum dorsally to facilitate entry of the endoscope into the rhinarium. Courtesy of Middlesex County Animal Hospital, MA, USA

Figure 9.

Gross endoscopic appearance of normal feline turbinate structure (a) and swollen, edematous turbinates (b). Note the smooth rounded linear appearance of the normal turbinates as compared with the blunted, irregular and tortuous appearance of the more abnormal turbinates. These findings are non-specific but are commonly associated with inflammatory rhinitis of various etiologies. Courtesy of Philip Lhermette

The dorsal nasal meatus should be examined as thoroughly as possible, rotating the endoscope very slightly right and left to navigate the ethmoid turbinates. It is very rare to be able to advance the endoscope all the way to the cribiform plate unless there is such dramatic and destructive disease that the turbinate structures are largely gone.

Careful note should be made of the colour and texture of the mucosa and the architecture of the turbinates.

Next the endoscope should be retracted (moved rostrally) slightly to allow for some observation of the ventral nasal meatus. The turbinate structures of the ventral nasal meatus are generally far less tortuous and essentially this is a path towards the posterior nares. Size being the limiting factor, it can be difficult to navigate the endoscope through the entirety of the ventral nasal meatus to the posterior nares. Polyps or masses may be observed obscuring passage through the ventral meatus as well as protruding from the slit-like opening of the Eustachian tube. If it proves impossible to confirm patency of the ventral nasal meatus through to the posterior nares, an instrument can be inserted via the endoscope through the ventral meatus, beyond the visual field of the surgeon. With a finger in the cat’s mouth the surgeon can feel over the back edge of the soft palate whether the instrument has come through, thus confirming patency.

Masses or polyp-type lesions noted in the rhinarium can be biopsied using the slender flexible endoscopic forceps designed for use with the particular endoscope, or a more robust rigid forceps inserted alongside the endoscope should space allow. A degree of hemorrhage is expected after biopsies are taken. It is good practice to perform a careful and delicate examination of the entire nose before biopsies are taken or masses resected. The resultant hemorrhage, while normal, can hamper further examination.

Diode laser therapy for nasal mass lesions

The diode laser, particularly at a wavelength at or near 810 nm, is a valuable tool in the management of mass lesions in the feline nose (Figures 10 and 11). These diodes perform especially well in fluid media (such as in irrigant solutions or hemorrhage) with minimal attenuation of energy. There is also a unique benefit to 810 nm due to the increased absorption of light at that wavelength by biological pigments (particularly hemoglobin, as well as melanin and others). This allows the operator to achieve excellent surgical results with a reduced amount of energy imparted to the patient, minimizing the risks of collateral thermal injury.

Figure 10.

(a,b) A right-angled laser fiber can be of great value in ablating lesions that occur at oblique angles relative to the long axis of the fiber. Here the diode laser is shown ablating a nasal adenocarcinoma

Figure 11.

(a,b) Diode lasers come in a variety of forms and sizes appropriate for different clinical settings. Images courtesy of Elexxion

The fiber is introduced to the surgical site via the instrument channel of the endoscope (Figure 12) and the tip of the fiber is held in direct apposition to the tissue of interest (‘direct contact mode’). In this manner, the tissue can be ablated and largely resected whether the lesion is neoplastic or benign. While it would be an overstatement to suggest that this approach is likely to produce clean surgical margins and, as such, complete resection, it is an excellent adjunctive therapy and can provide prolonged management of clinical signs.^2–4

Figure 12.

Surgeon pictured threading the laser fiber through the operating channel of the endoscope. Courtesy of Middlesex County Animal Hospital, MA, USA

Examination of the contralateral side

With the examination of one side complete, the rostral rhinoscopy procedure is performed in an identical manner on the contralateral side.

Sinusoscopy

If radiographs, CT/MR imaging or physical examination suggest the need, an endoscopic approach to the frontal sinuses can be undertaken. As there is no natural opening in this location the surgeon must, of course, provide some means of endoscopic ingress to the sinuses.

The dorsal-most point of the frontal sinus is identified by marking a point at the dorsal-most aspect of the orbit and approximately 2 cm towards the midline. This should correspond to the top of the dorsal shelf of the frontal sinus. In cases of pathology, this bone may be thin or completely eroded. Often there is a visible swelling over this site (the path of least resistance being the thinnest portion of the bone). With this point identified, the area is clipped, prepped and draped for aseptic surgery. A small incision is made with an #11 blade, the subcutaneous fascia retracted and the bone exposed.

A variety of methods can be used to make a hole through the frontal sinus bone. If accessible, a surgical drill (eg, Hall air drill or similar) can be used. A sterilized Dremel or small craft drill can also be used quite effectively. Alternatively, a very small diameter Michele trephine can be used, although often even the smallest available trephine is too large for feline patients. A Steinmann pin and Jacobs chuck of appropriate diameter for the endoscope to be used is often the simplest and most expeditious way of drilling a hole into the sinus.

Once access to the frontal sinus is obtained a rigid endoscope is generally used to examine the interior of the sinus. Often aggressive irrigation is needed to allow adequate visualization. Once the space is relatively clean, samples of tissue for histopathology, bacterial or fungal culture can be obtained and masses can be ablated or debulked. Closure of the access hole is generally accomplished with skin sutures only.

Tracheoscopy

Tracheoscopy for diagnostic purposes is generally performed with a flexible fiberoptic two-way deflection endoscope. Depending on the size of the patient, scopes with diameters of less than 4.8 mm are usually used. With care, rigid endoscopes can also be employed for tracheoscopy. Visualization with rigid scopes distal to the thoracic inlet can be difficult and potentially dangerous, however. Tracheal tears and perforations are a rare but serious complication of overzealous rigid endoscopy of the trachea.

Ideally, the endoscope should be small enough to allow for it to be used within the lumen of an endotracheal tube. However, the diameter of endoscopes commonly employed in feline practice makes this rarely possible. With larger feline patients that will accommodate an endotracheal tube of relatively greater diameter the patient can be maintained under inhalant gas anesthesia, with the anesthetic and oxygen flow maintained through a ‘Y’ adaptor via a side port. The central aperture of the adaptor is usually equipped with a silicon or latex gasket that allows for an endoscope to be passed with minimal loss of gas and oxygen. In this instance the endoscope is inserted beyond the distal tip of the endotracheal tube and the distal trachea is examined. To examine more proximal portions of the trachea, the cuff of the tube is deflated and the tube slowly removed with the endoscope still in place. This allows the endoscopist to visualize aspects of the trachea that were otherwise obscured by the presence of the endotracheal tube.

More commonly, the size of the endoscope relative to the size of the patient’s trachea makes concurrent placement of an endotracheal tube and endoscope impossible. In this instance, the patient is generally maintained under general anesthesia with intermittent boluses or a continuous infusion of propofol or similar short-acting injectable anesthetic agents. The author often passes a flexible silicone catheter into the trachea connected to passive flow-by oxygen to supplement the ambient air. It is important to keep in mind that complete airway control is not obtained in this instance and the anesthetist must be prepared to perform emergency intubation should it become necessary.

This same approach can be used to perform bronchoscopic examination of the lower airways with bronchoalveolar lavage and other lower airway studies (see accompanying article in this Special Issue on lower respiratory tract endoscopy).

Visual examination of the trachea is easily performed using these techniques. Cytologic samples can be obtained with endoscopic brushings and fluid aspirates. Biopsies of mass lesions can also be taken, but great care is required as iatrogenic pneumomediastinum and pneumothorax can be caused relatively easily by perforation of the tracheal membranes.

Figure 13.

Severe lymphoplasmacytic rhinitis. Courtesy of Philip Lhermette

Tracheal foreign body retrieval

For the purpose of tracheal foreign body retrieval rigid endoscopy is usually performed (Figure 14). Unfortunately, given the size of our feline patients it is often difficult to use a flexible endoscope of adequate size to allow for the use of appropriate retrieval devices. The smaller flexible endoscopes are more limited in the types of retrieval devices available, and these are less robust and generally less useful than their larger counterparts. As such, the use of a rigid scope, with a protective sheath, will allow the endoscopist to utilize a greater range of both rigid and flexible grasping instruments.

Figure 14.

(a,b) Tracheal foreign bodies are an infrequent cause of respiratory distress in cats. When attempting endoscopic retrieval the size of the foreign body and the location within the trachea must be considered. Images courtesy of Alasdair Hotston Moore

In these instances, the patient is generally maintained under injectable anesthetics, as noted earlier. Great care must be taken to avoid iatrogenic tracheal injury associated with removal of the offending foreign body. It is prudent for the surgeon to be prepared to perform an emergency tracheostomy in the event that the trachea is damaged in the process of removing the foreign body, or should the retrieval prove unsuccessful and an airway needs to be obtained distal to the site of the obstruction.

Key points

• The size of our feline patients does present some hurdles that need to be overcome to effectively use minimally invasive diagnostics and therapeutics in the management of nasopharyngeal and tracheal disease.

• Fortunately, the development of technologies that allow for appropriately sized instrumentation has facilitated access to these difficult to examine anatomic locations.

• With good training, patience and appropriate instrumentation both the general practitioner and referral feline veterinarian will find tremendous utility in endoscopic examination and minimally invasive surgery of the upper respiratory tract of the cat.

The author received no specific grant from any funding agency in the public, commercial or not-for-profit sectors for the preparation of this article.

The author does not have any potential conflicts of interest to declare.