Rhinoscopy In The Diagnostic Approach To Nasal Disease
Timothy C. McCarthy,
D.V.M., Ph.D., Diplomate ACVS
Rhinoscopy, endoscopic examination of the nasal cavity, nasal turbinates, nasopharynx, and frontal sinuses, has distinct advantages over other examination techniques for nasal disease diagnosis. Rhinoscopy is a noninvasive technique which is far less traumatic than surgical exploration, yet allows direct visualization of lesions for gross diagnosis and sample collection. The frontal sinuses can be examined through the nasal cavity in some cases or they can be accessed directly by trephining a hole in the outer table of the frontal bone. The presence of exudate and hemorrhage obscuring visualization, considered a disadvantage by many endoscopists, is not a problem if adequate irrigation is used during the examination.
Successful diagnosis of chronic nasal disease cases is greatly enhanced by a thorough and systematic approach centered around effective rhinoscopic examination. Rhinoscopy is essential to the diagnostic approach to nasal disease but cannot be relied on by itself to provide a diagnosis in all cases. The rhinoscopic technique employed by the author, in conjunction with a complete and organized diagnostic protocol, has been successful in establishing an accurate diagnosis in almost all cases of chronic nasal disease.
Diagnosis of nasal diseases is complicated by the similarity of signs presented by various nasal diseases and by inaccessibility of the nasal cavity for examination. A history and the physical findings associated with chronic nasal disease can be an indication of nasal neoplasia, mycotic rhinitis and sinusitis, foreign bodies, bacterial rhinitis and sinusitis, dental disease, allergic rhinitis, rhinitis from environmental irritants, parasitic rhinitis and numerous systemic diseases. Systemic signs that may be seen with nasal disease may include coughing, gagging and vomiting, loss of appetite, lethargy, weight loss and neurologic disorders. Nasal discharge may be mucoid, mucopurulent, purulent, with or without blood, or may be purely blood. Discharge may be unilateral or bilateral and may be continuous or intermittent. Other signs of nasal disease may include dyspnea, increased breathing sounds associated with partial nasal obstruction, epistaxis, facial swelling and distortion, facial or rostral nasal pain, sneezing, reverse sneezing, snorting, facial rubbing, ocular discharge, and dental disease. Unfortunately none of the above findings are specific and do not provide information necessary for establishing a diagnosis. The history and physical examination usually do nothing more than direct attention to the nasal cavity for additional evaluation.
Physical examination is directed at the systemic condition of the patient as well as the area of primary complaint. A large percentage of nasal disease patients are geriatric and systemic evaluation is essential to case management. Additional preanesthetic evaluation of the patient includes but is not limited to; CBC, blood chemistry profile, thyroid evaluation, UA, chest radiographs and EKG. Aspergillus and cryptococcosis serologic testing may be done prior to evaluation under anesthesia or may be delayed and done afterwards if another diagnosis is not established. Blood samples for allergy screening may also be drawn at this time or delayed and done only if indicated. When the above diagnostics have been completed the patient is anesthetized for nasal examination. Deep general anesthesia is essential for adequate rhinoscopic evaluation. The nasal cavity is very sensitive and sedation or a light plane of anesthesia are inadequate to allow rhinoscopy. Anesthesia is also required for adequate radiographic positioning and for culture sample collection. Sevoflurane or Isoflurane with oxygen have been the anesthetic protocols of choice. An endotracheal tube with an inflated cuff to produce a watertight seal is essential to prevent airway contamination during rhinoscopy.
The sequence of diagnostic events done under anesthesia is important in obtaining accurate and meaningful information. Radiographs are taken of the nasal cavity and frontal sinuses prior to any other procedures. Obtaining nasal cultures or biopsy samples or rhinoscopic examination may alter the radiographic appearance of the nasal cavity and therefore must be delayed until after radiographs have been taken. Culture samples are then obtained before the nasal cavity is invaded by rhinoscopic examination. Placement of the endoscope may cause contamination of the nasal cavity or more likely the fluid used for irrigation during examination will dilute or remove organisms. The oral cavity is examined thoroughly while the patient is under anesthesia including the teeth, gums, hard and soft palates, caudal pharyngeal area, and the caudal nasopharynx by rostral retraction of the soft palate. Rhinoscopy is done as the last step of the examination and tissue samples are collected for histopathology. When the rhinoscopic examination has been completed appropriate samples are selected depending on the findings of the evaluation. Not all samples collected in all cases are submitted. If a foreign body is found and removed biopsies are not taken and the culture and serology samples may be discarded. If a tumor is found biopsies are submitted and the culture and serology samples are held until a diagnosis is confirmed. If dental disease is diagnosed cultures are submitted while biopsy and serology are held until a response is seen to treatment. It is more economical to collect all necessary samples in the appropriate sequence while the patient is under anesthesia and to discard what is not needed than to reanesthetize the patient for more samples when the initial suspected diagnosis is not confirmed. If there is no obvious diagnosis when the rhinoscopic examination has been completed all samples are submitted.
Radiographic views obtained for nasal evaluation include four routine views and two optional views. Anesthesia is required for adequate radiographic positioning for nasal examination. The first routine view is a lateral projection centered over the nasal cavity and exposed for assessment of turbinate detail. Accurate lateral positioning for this view is assisted by superimposing the shadows of the upper carnassial teeth using the collimator light. The second view increases exposure and centers the projection further caudally to more accurately assess the nasopharyngeal area. The third routine view is an open mouth 20 degree caudal oblique ventrodorsal view which allows examination of the entire nasal cavity and extends caudally into the nasopharyngeal area. This projection is superior to an occlusal view with the film placed in the mouth. The fourth routine projection is a frontal sinus skyline rostrocaudal projection. Two optional views are obliques for assessment of the upper dental arcades.
Following radiographic examination culture samples are taken. The external nares and accessible portion of the rostral nasal passages are cleaned with a complete aseptic surgical preparation on the side selected for sample collection. A culture swab is then passed into the nasal cavity as far as it will go without resistance. Two separate culture swabs are used, one for bacterial culture and one for fungal culture. If fungal colonies are identified during rhinoscopy samples are taken of the colonies with biopsy forceps for culture. Diagnostic yield is higher with samples collected by this technique than with a swab.
The majority of rhinoscopic examinations have been performed using a 2.7mm diameter multipurpose rigid telescope with a 30 degree oblique viewing angle combined with a 4.0mm arthroscopy cannula having a working length of 143 cm. This instrument is well suited for rhinoscopy because it allows irrigation through the endoscope during examination and its small size allows examination of most small animal patients. Its primary disadvantage is that it does not have an instrument channel for passing biopsy forceps. Thus biopsies must be taken by passing the biopsy forceps beside the endoscope and aligning the endoscope and biopsy forceps so that the tip of the forceps is visible in the endoscope field. Biopsies are then taken under direct visualization. An alternative system that also works well for rhinoscopy is a 4.0mm by 5.5mm oval cystoscopy cannula with a 165mm working length and a 5 french biopsy channel. This cannula is used with the same 2.7mm diameter multipurpose rigid telescope. The major advantage of this cannula is that it facilitates placement of biopsy forceps. It has the disadvantage of allowing collection of much smaller biopsy samples. A Storz 1.9mm diameter arthroscope with a 30 degree viewing angle has also been utilized for rhinoscopy and its smaller size has been found to be an advantage in very small dogs and in cats. Arthroscopy and cystoscopy cannulas are available of use with this telescope. Flexible endoscopes are much less effective for rhinoscopy and are not recommended.
Accessory instrumentation utilized for rhinoscopy include: A rigid 2.5mm diameter apposing cup biopsy forceps with 145mm working length, flexible 1.6mm diameter apposing cup biopsy forceps with 282mm working length, flexible 1.6mm diameter grasping forceps with 282mm working length, alligator forceps with 160 mm working length for foreign body removal.
Irrigation of the nasal cavity through the endoscope during the procedure is essential for examination. This is accomplished with liter containers of sterile physiologic saline solution or sterile Ringers solution and an intravenous administration set attached to the irrigation port of the arthroscopy or cystoscopy cannula. Fluids containing dextrose are not recommended because cleanup after the procedure is more difficult. The fluid container is placed a convenient height above the patient, usually about 70 cm.
If irrigation is not employed visibility is obscured by exudate and blood and nothing can be seen. With irrigation any exudate or blood from the primary disease or from bleeding induced by examination or biopsies is washed away from in front of the endoscope lens and examination can be performed. In the presence of copious exudate extensive irrigation may be required before adequate examination can be carried out. Irrigation through the endoscope cannula is sufficient to clear the nasal cavity for examination in almost all cases. Additional irrigation or vigorous flushing with a syringe may occasionally be required when a large quantity or thick exudate is present. For small dogs and for cats a twelve to twenty cc syringe is used and for larger dogs a sixty cc catheter tip syringe is employed.
For rhinoscopy the patient is placed in lateral recumbency with its head on an absorbent towel and the rostral end of the nose extending over the edge of the examination table. Alternate positioning with the patient in ventral recumbency can be utilized depending on the preference of the examiner. A waste container is placed under the table directly below the patientís nose to catch runoff irrigant. If the examiner is seated, his or her knees are covered with absorbent towels or waterproof drape material.
If bilateral disease is present the side examined first is of no importance. If unilateral disease is present the normal side is usually evaluated first to minimize changes induced by fluid, exudate, and blood from examination of the abnormal side. Careful examination of the normal nasal cavity will produce limited bleeding and will not have a significant impact on findings in the abnormal side. A systematic approach to examination of the nasal cavity is taken to insure examination of all accessible areas but an attempt is not made to identify all the normal anatomic structures and turbinates. The entire nasal cavity cannot be examined endoscopically with rigid instrumentation or with currently available flexible instrumentation. A significant portion of the nasal cavity can however be examined even in small dogs and cats.
Bleeding does occur during rhinoscopy. With irrigation the quantity of hemorrhage is rarely enough to interfere with examination. Occasionally there is profuse bleeding after obtaining biopsies that may make further examination or sample collection more difficult. For this reason the entire examination is performed before biopsy samples are taken. Bleeding induced by rhinoscopy has not produced sufficient blood loss to endanger the patient.
Multiple biopsy samples are harvested to increase the tissue available for the pathologist and to sample different tissue sites. For multiple sample collection the endoscope position may be maintained and the biopsy forceps removed and reinserted with each sample or both the endoscope and biopsy forceps may be removed with each sample. The technique employed will in some cases be dictated by the location or size of the lesion or by patient size or confirmation. When foreign bodies are found they are removed with appropriate forceps. A pair of 160mm (6 inch) alligator forceps works well in most cases. If the foreign material is small it can be removed rostrally through the external nares. Foreign bodies that are too large to remove rostrally are pushed caudally through the nasopharynx for removal. Foreign bodies may be multiple so the entire nasal cavity is carefully assessed.
When rhinoscopy has been completed the pharyngeal area is cleaned to remove fluid, debris, and blood clots. The external nares and pharyngeal area are monitored for excessive bleeding. Patient recovery is delayed until all bleeding has stopped and is then allowed to be slow and quiet with minimal stimulus. Sedation is used as needed to prevent rapid recovery. It is strongly recommended that these patients be hospitalized for the night after the procedure even if they are adequately recovered from anesthesia for release. If they are allowed to rest quietly overnight after the procedure epistaxis is minimal. The stimulus and excitation produced by reunion with the owner and release from the hospital can frequently induce epistaxis. Post rhinoscopy epistaxis has not been sufficient to be a risk for the patient but epistaxis combined with sneezing and excitement can cause considerable anxiety for the owner.
The reduced morbidity of rhinoscopy when compared with surgery and the high diagnostic success rate with this protocol has eliminated the need for exploratory rhinotomy.