Topics in Compan An Med 28 (2013) 97–102
Topical Reviews
Transtracheal Wash and Bronchoalveolar Lavage Maureen D. Finke, DVM, DACVIMn Keywords: respiratory bronchoscopy trachea cytology culture Wheat Ridge Veterinary Specialists, Wheat Ridge, CO, USA
Examination and sampling of the pulmonary airways can be of great benefit in patients with respiratory disease. Transtracheal and endotracheal washes are minimally invasive procedures that allow for blind sampling of the larger airways for cytologic and culture analysis. Flexible tracheobronchoscopy allows for direct visualization of the trachea, bronchi, and oropharynx. Bronchoalveolar lavage helps to obtain samples from the small airways and alveoli during bronchoscopy. The combined use of these techniques can help clinicians diagnose challenging respiratory cases. The following article reviews the indications and techniques of these procedures. & 2013 Elsevier Inc. All rights reserved.
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Address reprint requests to Maureen D. Finke, DVM, DACVIM, Small Animal Internal Medicine, Wheat Ridge Veterinary Specialists, 3695 Kipling Street, Wheat Ridge, CO 80033. E-mail: mfi[email protected]
Introduction Transtracheal Wash (TTW) TTW is a minimally invasive procedure used to sample the larger airways (e.g., trachea and mainstem bronchi) of dogs. In case of lower airway or interstitial lung disease, the results have been shown to be inferior to samples obtained by bronchoalveolar lavage (BAL).1 TTW has the benefit of being performed in awake patients, bypassing the need for anesthesia in a patient with respiratory compromise. Because the animal is not sedated, there is the additional benefit of an intact cough response, which may result in some expectoration of samples from the lower airways.
Technique TTWs are usually performed using a through-the-needle, long intravenous catheter. These catheters are easy to use and have the advantage of allowing removal of the needle from the trachea once the catheter is in place. Alternatively, a 14- or 16-gauge needle or over-the-needle catheter can be placed percutaneously into the trachea and a long, red, rubber or polypropylene catheter can be fed through the needle and into the trachea. Strict asepsis should be performed throughout the procedure. Place the patient in either sternal recumbency or in a sitting position with the neck extended and the nose elevated. Shave and aseptically scrub the ventral neck including the larynx and cervical trachea. Infuse a local anesthetic drug (2% lidocaine) into the skin and subcutaneous (SQ) tissues. While the local anesthetic is taking effect, preload several syringes with 5-20 mL of sterile, nonbacteriostatic 0.9% saline. The operator should wear sterile gloves and use aseptic technique throughout the procedure. Palpate the cricothyroid ligament as a triangular depression distal to the thyroid cartilage. The needle can be placed either through the cricothyroid ligament or between 2 tracheal rings just distal to the larynx. With the bevel facing ventrally, insert the needle through the skin and cricothyroid ligament into the tracheal lumen. A slight “pop” can be felt as the ligament is passed. Retching has been reported when using the cricothyroid approach
and may make the procedure more difficult.2 Alternatively, the needle can be passed between 2 tracheal rings on midline, just ventral to the larynx. Once the needle is in the tracheal lumen, angle the needle down approximately 451 and feed the catheter into the tracheal lumen. If the needle is properly placed, there should be minimal resistance as the catheter is advanced. If resistance is encountered, this may be owing to the needle being against the far (dorsal) wall of the trachea, in which case the needle can be pulled back slightly and the catheter is reinserted without resistance. If resistance is persistent, the needle is likely in surrounding tissue and not within the tracheal lumen. If this is the case, remove the needle and re-direct. As the catheter is passed down the tracheal lumen, the dog may cough and may become slightly agitated. Once the catheter is in place, the needle is removed from the trachea. If it is a throughthe-needle catheter, place the guard over the needle. If a 16-gauge needle or an over-the-needle catheter was used, pull the needle back out of the trachea and over the catheter. Attach the preloaded syringe to the catheter and infuse the sterile saline into the trachea. It may be helpful to have an assistant perform coupage during instillation of the fluid so as to promote coughing. Aspirate the infused saline back into the syringe. If excess air is aspirated, the syringe may need to be detached from the catheter and the excess air expelled so as to aspirate as much fluid back as possible. It is common to recover only 10% or less of the infused volume. If desired, the procedure can be repeated with a second preloaded syringe. Once an adequate sample has been obtained, remove the syringe and catheter from the neck in a smooth motion. Place a soft, padded bandage over the catheter site for approximately 1 hour to minimize the formation of SQ emphysema.
Endotracheal Wash (ETW) ETW sampling is recommended in smaller patients (cats and dogs o10 kg) as their smaller tracheal lumen diameter precludes placement of a large needle between tracheal rings. ETW should also be considered in larger dogs that are fractious or resistant to
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restraint and in which performing a transtracheal wash could result in clinician or patient injury. General anesthesia is required for ETW and therefore may potentially result in more risk to the patient. Because anesthesia prevents a cough reflex, recovered fluid is more likely to represent large airway findings and therefore may be less diagnostic. With this technique, there is also more risk of contamination from the oropharynx Before anesthesia, preoxygenate the patient for 5-10 minutes. During this period of time, preload syringes with sterile, nonbacteriostatic 0.9% saline. Owing to the risk of bronchospasm during the procedure, bronchodilators are recommended in cats and may be considered in dogs with suspected inflammatory airway disease. Terbutaline (0.01 mg/kg SQ q 8 hours) can be administered 12-24 hours before the procedure, with the final dose given 2-4 hours before anesthetic induction. Owing to the inability to provide oxygen and inhalant anesthesia during the procedure, most patients are induced with injectable anesthetics such as propofol. These short-acting anesthetics also allow for quick recovery after the procedure. Similar to a TTW, aseptic technique should be followed for an endotracheal lavage. Place the patient in sternal or lateral recumbency with the affected side down. Carefully pass a sterile ET tube through the arytenoid cartilages into the trachea, taking care to avoid contaminating the tube with oropharyngeal secretions. Do not attach the anesthesia machine tubing to the ET tube until after the wash has been performed. Once the patient is intubated, feed a red rubber catheter (8 Fr) through the ET tube, being careful to maintain sterility. Attach a preloaded syringe to the catheter and infuse the contents through the catheter as previously described. The red rubber catheter may need to be shortened or a catheter adapter may need to be used to secure the syringe to the catheter. Aspirate the infused saline back into the syringe.
Bronchoscopy Endoscopic examination of the respiratory system is useful in the diagnosis of airway disease in dogs and cats. Tracheobronchoscopy should be considered in patients with acute or chronic cough, stridor, hemoptysis, or respiratory distress, when other diagnostics have not identified an underlying cause. Endoscopy allows for direct visualization of the lumen of larger airway and allows for sampling of cells, fluid, and infectious organisms from the airways by using BAL, bronchial brushing, or biopsy. Bronchoscopy is most helpful in patients with airway disease and may be less diagnostic in patients that have interstitial or isolated focal parenchymal pulmonary lesions. Equipment Both rigid and flexible endoscopes can be used to examine the respiratory system. Descriptions of equipment available for use in veterinary tracheobronchoscopy have been discussed elsewhere.3,4 Briefly, the use of rigid scopes is more limited but allows examination of the larynx, trachea, and carina. A flexible endoscope is required for examination of the segmental bronchi. The bronchoscope should contain an instrument channel (for biopsy and brush forceps and to obtain BAL samples), suction, and a light source and have the ability to perform bilateral tip deflection to direct the scope into appropriate airways. Anesthesia General anesthesia is required to perform bronchoscopy. All patients should be preoxygenated for at least 5-10 minutes before
anesthesia induction. Bronchodilator therapy as previously mentioned is recommended in feline patients before bronchoscopy, BAL, and ETW. Inhalant anesthesia is almost always utilized except in cats and very small dogs. In these patients, endotracheal intubation is not possible, as the bronchoscope would not fit through a small ET tube. In those patients, injectable propofol anesthesia is titrated to effect. A small diameter polypropylene catheter can be passed down the trachea to provide oxygen. Alternatively, some clinicians prefer to provide oxygen via jet ventilation or through the working channel of the scope.5-7 It is important to realize that the tracheal lumen may be completely occluded by the bronchoscope in small patients and hypoxia and hypercapnia may occur. It is recommended to perform airway examination and diagnostic sampling at several brief periods in these patients. The use of topical lidocaine and sterile lubricant can be used to prevent laryngospasm and arytenoid trauma as the scope is passed through the larynx multiple times. In patients that are large enough to allow inhalant anesthesia, place a sterile ET tube and take care to not contaminate the tube with oropharyngeal secretions during placement. A sterile Y- or T-shaped ET tube adapter can be used to allow passage of the endoscope into the ET tube while simultaneously allowing for oxygen and gas anesthesia delivery. Use a mouth gag to protect the bronchoscope from trauma in the unforeseen event of the patient awakening because of an insufficient plane of anesthesia. Anatomy Canine tracheobronchial anatomy has been well described and a systematic nomenclature scheme has been developed8 (Fig 1). The anatomy of the cat is not as well described, but most clinicians use the same nomenclature in this species although differences do exist. The use of a standardized nomenclature scheme helps clinicians describe the location of airway sampling or of lesions accurately and serves as a map that helps keep the operator aware of the scope's location in the airways throughout the procedure. The airways branch quickly and it is easy to become lost. If this happens, it is helpful to return the scope to the carina to orient the operator to location and then go directly back to the area of interest. Procedure Pass the bronchoscope either through the ET tube in larger patients or directly through the larynx in small patients as noted earlier. It is important to realize that the tracheobronchial airways are rigid and undue force with the scope can damage the airway mucosa resulting in hemorrhage or even tearing of the airway wall. For this reason, advance the scope carefully without force. First examine the trachea, then the carina. Next, evaluate the bronchi in a systemic consistent manner. The author examines the right mainstem bronchus first, following the segmental bronchi into the right cranial lobe until the scope reaches its limit. Next, return the scope to the carina for orientation and then examine the segmental bronchi of the right middle lobe. Repeat these steps until all lung lobes have been examined. Complete the visual examination before performing any sampling procedures. Normal tracheobronchial mucosa is smooth and pink with minimal secretions (Fig 2). Erythema indicates inflammation and excessive mucus can be seen with many inflammatory conditions such as bronchitis. Yellow or greenish mucopurulent exudate may be seen in cases of pneumonia or eosinophilic pneumonopathy9 (Fig 3). The trachea should be round and patent with easily visible tracheal rings. Tracheal collapse can be identified and the extent of lumen occlusion used to classify the grade of collapse10 (Fig 4). The dorsal tracheal membrane can be visualized as a narrow band of tissue. It should be tightly adhered to the dorsal tracheal wall and
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Fig. 1. Bronchoscopic anatomy of the dog. (From Amis TC, McKiernan BC. Systematic identification of endobronchial anatomy during bronchoscopy in the dog. Am J Vet Res 1986;47(12):2655; with permission.)
should not droop or occlude the lumen in any way. The carina should be a sharply demarcated division into right and left mainstem bronchi. Edema and inflammation can cause widening of the carina and narrowing or irregularity of the airway lumen. Bronchi should always be round, patent during all phases of respiration and well defined. Bronchomalacia, weakness of the bronchi that results in collapse of the airway during respiration, is often seen in conjunction with tracheal collapse11,12 (Fig 5). Bronchiectasis, abnormal dilation of the bronchi, may be seen secondary to chronic inflammatory disorders such as chronic bronchitis or eosinophilic pneumonopathy and can also be secondary to congenital anatomic defects13 (Fig 6). Pulmonary submucosal vessels are easily visualized and should not be enlarged, distended, or tortuous.3,7,14 Tracheal foreign bodies and tumors may also be visualized (Figs 7 and 8). When abnormalities are noted, record their location, severity, and description. Take digital photographs of any area of interest.
Fig. 2. Normal canine carina.
Digital videography can be used to document dynamic lesions such as tracheal or bronchial collapse. Once the visual examination is complete, sampling of the airways via BAL can be performed.
BAL BAL should always be performed after a thorough and systematic examination of the airways. After bronchoscopic examination of the lung lobes, the endoscope should be removed from the airways and the biopsy channel flushed with sterile saline. The scope can also be wiped down with sterile saline at this time. To get a representative sample, an adequate volume of fluid must be infused. The proper amount of saline to be infused is controversial with many different published recommendations. Both weightadjusted and fixed amounts of BAL volumes have been suggested.
Fig. 3. Thick greenish exudate in a canine patient with chronic bronchopneumonia. Notice the irregular proliferation of the bronchial wall.
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Fig. 4. Tracheal collapse in a dog.
Fig. 6. Severe bronchiectasis in a canine patient with chronic bronchitis.
For dogs, aliquots of 15-25 mL per wash have been recommended.1,14-16 In cats, owing to their smaller lung volume, aliquots of 3-10 mL per site are used.6,16,17 Other authors recommend choosing aliquot volumes based upon body weight. In dogs, a volume of 1 mL/kg per aliquot is usually recommended whereas in cats, 3-5 mL/kg is used.15,18,19 A recent study investigated the use of fixed-amount BAL compared with volumes based upon body weight. This study found that choosing volume on an milliliter per kilogram basis resulted in more uniform recovery of BAL fluid.15 Regardless of volume chosen, most authors recommend performing at least 2 washes at each site. The number of sites sampled depends on the patient's underlying disease. For patients with diffuse lung disease, at least 2 different lung lobes should be sampled. For patients with very focal disease (such as aspiration pneumonia), it may be necessary to perform a BAL only on the affected lung lobe. To perform a BAL, pass the endoscope through the airways into the smallest bronchus that will accommodate it, then gently wedge it in place as distally as possible. A tight fit of the scope in the bronchus is essential to facilitate retrieval of infused saline. Once the bronchoscope is wedged in place, attach a syringe preloaded with sterile nonbacteriostatic saline, as previously described, to the biopsy channel of the scope. It may be helpful to follow the saline infusion with 3-5 mL of air to make sure all fluid reaches the lung lobe. Retrieve the infused saline through the biopsy channel by gentle suction using the same syringe. The syringe can be detached
from the biopsy channel port and air expelled so that as much fluid as possible can be recovered. Ideally, retrieval of BAL fluid should be done with the scope in the same wedged position to regain as much fluid as possible. If no saline is retrieved, it may be because of airway collapse and less suction should be applied to the syringe. If negative pressure is still present, the scope can be pulled back a few millimeters but in this case, the volume of recovered fluid may be less. The use of vacuum suction and a specimen trap container has also been reported.7 The sample of retrieved BAL fluid should contain a layer of foamy surfactant that rises to the top of the fluid. The presence of surfactant is an indicator that the sample was obtained from the lower airways. Another indicator of a good BAL sample is recovery of approximately 50% of the infused saline. In dogs, median recoveries of 42%-48% of the infused saline have been reported.1,20 In cats, retrieval of 50%-75% of BAL fluid was reported in a retrospective study of 68 cats.19 Samples obtained via BAL should be placed on ice while further washes are being performed until the samples can be processed.
Fig. 5. Expiratory collapse of a lobar bronchus in a dog with bronchomalacia secondary to chronic bronchitis.
Fig. 7. A foreign body in the trachea of a dog. This rock was successfully removed using a retrieval device.
Complications of Lavage or Wash Procedures Following any airway wash procedures, all patients should receive supplemental oxygen via ET tube. Arterial oxygen tension
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Table Reported Total and Differential Cell Counts from Healthy Dogs and Cats Canine BAL Normals28 Total cell count (per μL) Neutrophils (%) Macrophages (%) Lymphocytes (%) Eosinophils (%)
Fig. 8. A tracheal mass almost completely obstructing the lumen of a cat's trachea. The mass was successfully debulked and histology demonstrated a carcinoma.
(PaO2) and oxygen saturation may be transiently decreased in healthy patients after BAL. Patients that are already affected with respiratory compromise may be more susceptible to decreases in pulmonary function. After 5 minutes, attempt to wean the patient off of supplemental oxygen. If cyanosis or decreases in oxygen saturation are noted, further oxygen supplementation is necessary. If the patient is recovering from anesthesia, it may be acceptable to continue oxygen supplementation via facial mask or oxygen cage. If the patient cannot be weaned off of supplemental oxygen, other causes such as bronchospasm or pneumothorax should be considered. Both injectable and inhaled bronchodilators have been used after BAL to alleviate bronchospasm.21 Tracheal laceration, SQ emphysema, and pneumomediastinum have been reported after TTW.2 It is also possible to sever the catheter during a TTW, which could result in a tracheal or bronchial foreign body. Transient worsening of respiratory distress or cough can occur after any lavage procedure. Spontaneous pneumothorax has been rarely reported after BAL.19 Rarely, complications from BAL may be fatal. In a retrospective study at a referral institution, 2 of 101 (2%) dogs died after BAL.1 Both of these patients were in respiratory distress before the procedure. In a retrospective study of cats, 4 of 68 cats (6%) were euthanized after BAL owing to an inability to restore adequate oxygenation and ventilation after the procedure.19
Fluid Analysis For best results, processing of TTW, ETW, and BAL samples should be performed within 1 hour of collection. When assessing cytology, lavage samples from each lobe should be assessed separately. In one study, 37% of dogs had differing results when samples from various lung lobes were evaluated.1 Total nucleated cell counts can be performed using a hemocytometer. Differences in technique and concentration of recovered fluid make normal total cell counts from BAL controversial. Because all wash samples are very dilute, cytocentrifugation techniques are recommended to concentrate the sample and increase the ease of assessing cytologic morphology and performing differential cell counts. Differential cell counts should be performed on every sample. A minimum of 200 cells should be counted, and one study suggested that more reproducible results can be reached if 500 cells are counted.18 The most common cell type recovered in BAL is the alveolar macrophage (4 70% in both dogs and cats).5,6,20 Cats normally contain higher numbers of eosinophils in BAL fluid than
200 5 70 7 6
7 7 7 7 7
86 5 11 5 5
Feline BAL Normals5,6 337 5 78 1 16
7 7 7 7 7
194 5 15 1 14
other species5,6 (Table). In contrast, the most common cell type in ETW and TTW is the neutrophil as the sample is from the larger airways and alveoli are not sampled.4 Samples obtained via ETW should always be evaluated for evidence of oropharyngeal contamination such as Simonsiella organisms. Interestingly, in a study of dogs with respiratory disease, almost half of the dogs had different categories of inflammation or a different diagnosis was reached when BAL and TTW fluid was compared. In half of the dogs (5/10), the bacterial culture was positive on BAL but negative on TTW. Overall, the diagnosis was different in 68% of the dogs.1 This suggests that for lower airway disease, BAL is superior to sampling via TTW. In dogs with spontaneous respiratory disease, neutrophilic or mixed inflammation is the most common abnormality found. Most dogs with bacterial infection have neutrophilic inflammation. Intracellular bacteria may be found.1 In dogs with chronic bronchitis, a mixed inflammatory or neutrophilic inflammation is seen most commonly. Increased numbers of eosinophils (20% to 4 50%) are seen in dogs with eosinophilic bronchopneumopathy.9 Activated macrophages may contain phagocytized organisms or red blood cells. Mixed inflammation is often seen with fungal infections. The presence of fungal organisms should be considered diagnostic. Differential cell counts can also be helpful in cats with lower airway disease. Neutrophilic inflammation with or without the presence of intracellular bacteria may be observed in cats with pneumonia. Cats with bronchitis or asthma often have an increased population of eosinophils. However, neutrophilic and eosinophilic inflammation is not pathognomonic for an infectious or immune-mediated process, as both eosinophilic and neutrophilic inflammation can also be observed with neoplasia.17 It can be difficult to reach a diagnosis of neoplasia from a sample obtained via BAL. All cells should be examined for criteria of malignancy. In the presence of concurrent inflammation however, care should be taken when interpreting malignancy. In a small study, cats with histologically diagnosed carcinoma showed neutrophilic inflammation but no evidence of cancer on cytology of fluid obtained via BAL.22 Another study showed considerable overlap of differential cell counts in cats with pneumonia, bronchitis, or neoplasia.17 Because of this, BAL cell counts should always be interpreted in combination with clinical signs and radiographic and bronchoscopic findings. Cultures The respiratory tree of normal healthy dogs is not sterile. Oropharyngeal contamination can result in false-positive results of any airway sample. Quantitative bacterial cultures may help to differentiate between contamination and true airway infections. More than 1.7 103 colony-forming units per milliliter obtained by quantitative bacterial culture has been shown to be sensitive and specific for bacterial bronchopneumonia.23 Aerobic and mycoplasma cultures should be performed on all airway samples.24 Fungal cultures may also be recommended in endemic areas. Fungal antigen testing has also been performed on BAL samples to diagnose histoplasmosis and blastomycosis in dogs. However,
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sensitivity is greater with serum or urine antigen testing for these diseases.25 In humans, coccidioidomycosis antigen testing can be performed on BAL samples. However, in dogs, sensitivity of antigen testing for coccidioidomycosis is poor at less than 20% and is not recommended. Polymerase Chain Reaction (PCR) Molecular diagnostics including PCR are an area of great interest in the diagnosis of many small-animal infectious diseases. The use of PCR on airway wash samples has been reported to diagnose Mycoplasma species, Bordetella bronchiseptica, and Toxoplasma gondii.24,26,27 PCR results should be interpreted with caution. Organisms such as Mycoplasma and Bartonella can be normal inhabitants of the oropharynx of dogs and cats. Therefore, a positive result does not guarantee that the pathogen is causing the patient's current clinical signs. In addition, a negative result does not rule out infection. Although the organism may be present in the airways, it may not be present in the small sample used for DNA extraction, resulting in a false-negative test.
Conclusion Respiratory airway disease can be a diagnostic challenge. Although history, physical examination, and thoracic radiographs often help clinicians reach a diagnosis, occasionally further diagnostics are necessary. In patients with airway disease, visualization of the airways can be a powerful diagnostic tool. Sampling the airways via TTW or BAL allows for cytologic and culture analysis of airway secretions. These modalities may allow for confirmation of chronic inflammatory conditions or allow for identification of infectious organisms. The diagnostic value of these tests cannot be overemphasized. Because patients with airway disease have increased risks with anesthesia and respiratory procedures, the risk of the procedure should always be weighed against the value of the expected results. References 1. Hawkins EC, DeNicola DB, Plier ML. Cytologic analysis of bronchoalveolar lavage fluid in the diagnosis of spontaneous respiratory tract disease in dogs: a retrospective study. J Vet Intern Med 9:386–392, 1995 2. Syring RS. Tracheal washes. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 128–134 3. Kuehn NF, Hess RS. Bronchoscopy. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 112–118 4. McKiernan BC. Bronchoscopy. In: McCarthy TC, editor. Veterinary Endoscopy for the Small Animal Practitioner. St. Louis: Elsevier Saunders; 2005. p. 201–227
5. Hawkins EC, Kennedy-Stoskopf S, Levy J, et al. Cytologic characterization of bronchoalveolar lavage fluid collected through an endotracheal tube in cats. Am J Vet Res 55:795–802, 1994 6. Padrid PA, Feldman BF, Funk K, Samitz EM, Reil D, C.E. Cross. Cytologic, microbiologic, and biochemical analysis of bronchoalveolar lavage fluid obtained from 24 healthy cats. Am J Vet Res 52:1300–1307, 1991 7. Creevy KE. Airway evaluation and flexible endoscopic procedures in dogs and cats: laryngoscopy, transtracheal wash, tracheobronchoscopy, bronchoalveolar lavage. Vet Clin Small Anim 39:869–880, 2009 8. Amis TC, McKiernan BC. Systemic identification of endobronchial anatomy during bronchoscopy in the dog. Am J Vet Res 47:2649–2657, 1986 9. Clercx C, Peeters D, Snaps F, et al. Eosinophilic bronchopneumopathy in dogs. J Vet Intern Med 14:282–291, 2000 10. Mason RA, Johnson LR. Tracheal collapse. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 346–355 11. Adamama-Moraitou KK, Pardali D, Day MJ, et al. Canine bronchomalacia: a clinicopathological study of 18 cases diagnosed by endoscopy. Vet J 191: 261–266, 2010 12. Johnson LR, Pollard RE. Tracheal collapse and bronchomalacia in dogs: 58 cases (7/2001-1/2008). J Vet Intern Med 24:298–305, 2010 13. Norris CR. Bronchiectasis. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 376–379 14. Mercier E, Bolognin M, Hoffmann AC, Tual C, Day MJ, Clercx C. Influence of age on bronchoscopic findings in healthy beagle dogs. Vet J 187:225–228, 2011 15. Melamies MA, Jarvinen AK, Seppala KM, Rita HJ, Rajamaki MM. Comparison of results for weight-adjusted and fixed-amount bronchoalveolar lavage techniques in healthy Beagles. Am J Vet Res 72:694–698, 2011 16. Dehard S, Bernaerts F, Peeters D, et al. Comparison of bronchoalveolar lavage cytospins and smears in dogs and cats. J Am Anim Hosp Assoc 44: 285–294, 2008 17. Johnson LR, Vernau W. Bronchoscopic findings of 48 cats with spontaneous lower respiratory tract disease (2002-2009). J Vet Intern Med 25:236–243, 2011 18. De Lorenzi D, Masserdotti C, Bertoncello D, Tranquillo V. Differential cell counts in canine cytocentrifuged bronchoalveolar lavage fluid: a study on reliable enumeration of each cell type. Vet Clin Pathol 38:532–536, 2009 19. Johnson LR, Drazenovich TL. Flexible bronchoscopy and bronchoalveolar lavage in 68 cats (2001-2006). J Vet Intern Med 21:219–225, 2007 20. Hawkins EC, Rogala AR, Large EE, Bradley JM, Grindem CB. Cellular composition of bronchial brushings obtained from healthy dogs and dogs with chronic cough and cytologic composition of bronchoalveolar lavage fluid obtained from dogs with chronic cough. Am J Vet Res 67:160–167, 2006 21. Kirschvink N, Leemans J, Delvaux F, Snaps F, Clercx C, Gustin P. Bronchodilators in bronchoscopy-induced airflow limitation in allergen-sensitized cats. J Vet Intern Med 19:161–167, 2005 22. Norris CR, Griffey SM, Samii VF, Christopher MM, Mellema MS. Thoracic radiography, bronchoalveolar lavage cytopathology, and pulmonary parenchymal histopathology: a comparison of diagnostic results in 11 cats. J Am Anim Hosp Assoc 38:337–345, 2002 23. Peeters DE, McKiernan BC, Weisiger RM, Schaeffer DJ, Clercx C. Quantitative bacterial cultures and cytological examination of bronchoalveolar lavage specimens in dogs. J Vet Intern Med 14:534–541, 2000 24. Chalker VJ, Owen WM, Paterson C, et al. Mycoplasmas associated with canine infectious respiratory disease. Microbiology 150:3491–3497, 2004 25. Spector D, Wheat J, Beamis D, Rohrbach B, Taboada T, Legendre AM. Antigen testing for the diagnosis of Blastomycosis. J Vet Intern Med 20:711–712, 2006 26. Egberink H, Addie D, Belak S, et al. Bordetella bronchiseptica infections in cats. J Fel Med Surg 11:610–614, 2009 27. Anfray P, Bonetti C, Fabbrini F, Magnino S, Mancianti F, Abramo F. Feline cutaneous toxoplasmosis: a case report. Vet Dermat 16:131–136, 2005 28. Hawkins EC. Bronchoalveolar lavage. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 118–128
Topical Reviews
Transtracheal Wash and Bronchoalveolar Lavage Maureen D. Finke, DVM, DACVIMn Keywords: respiratory bronchoscopy trachea cytology culture Wheat Ridge Veterinary Specialists, Wheat Ridge, CO, USA
Examination and sampling of the pulmonary airways can be of great benefit in patients with respiratory disease. Transtracheal and endotracheal washes are minimally invasive procedures that allow for blind sampling of the larger airways for cytologic and culture analysis. Flexible tracheobronchoscopy allows for direct visualization of the trachea, bronchi, and oropharynx. Bronchoalveolar lavage helps to obtain samples from the small airways and alveoli during bronchoscopy. The combined use of these techniques can help clinicians diagnose challenging respiratory cases. The following article reviews the indications and techniques of these procedures. & 2013 Elsevier Inc. All rights reserved.
n
Address reprint requests to Maureen D. Finke, DVM, DACVIM, Small Animal Internal Medicine, Wheat Ridge Veterinary Specialists, 3695 Kipling Street, Wheat Ridge, CO 80033. E-mail: mfi[email protected]
Introduction Transtracheal Wash (TTW) TTW is a minimally invasive procedure used to sample the larger airways (e.g., trachea and mainstem bronchi) of dogs. In case of lower airway or interstitial lung disease, the results have been shown to be inferior to samples obtained by bronchoalveolar lavage (BAL).1 TTW has the benefit of being performed in awake patients, bypassing the need for anesthesia in a patient with respiratory compromise. Because the animal is not sedated, there is the additional benefit of an intact cough response, which may result in some expectoration of samples from the lower airways.
Technique TTWs are usually performed using a through-the-needle, long intravenous catheter. These catheters are easy to use and have the advantage of allowing removal of the needle from the trachea once the catheter is in place. Alternatively, a 14- or 16-gauge needle or over-the-needle catheter can be placed percutaneously into the trachea and a long, red, rubber or polypropylene catheter can be fed through the needle and into the trachea. Strict asepsis should be performed throughout the procedure. Place the patient in either sternal recumbency or in a sitting position with the neck extended and the nose elevated. Shave and aseptically scrub the ventral neck including the larynx and cervical trachea. Infuse a local anesthetic drug (2% lidocaine) into the skin and subcutaneous (SQ) tissues. While the local anesthetic is taking effect, preload several syringes with 5-20 mL of sterile, nonbacteriostatic 0.9% saline. The operator should wear sterile gloves and use aseptic technique throughout the procedure. Palpate the cricothyroid ligament as a triangular depression distal to the thyroid cartilage. The needle can be placed either through the cricothyroid ligament or between 2 tracheal rings just distal to the larynx. With the bevel facing ventrally, insert the needle through the skin and cricothyroid ligament into the tracheal lumen. A slight “pop” can be felt as the ligament is passed. Retching has been reported when using the cricothyroid approach
and may make the procedure more difficult.2 Alternatively, the needle can be passed between 2 tracheal rings on midline, just ventral to the larynx. Once the needle is in the tracheal lumen, angle the needle down approximately 451 and feed the catheter into the tracheal lumen. If the needle is properly placed, there should be minimal resistance as the catheter is advanced. If resistance is encountered, this may be owing to the needle being against the far (dorsal) wall of the trachea, in which case the needle can be pulled back slightly and the catheter is reinserted without resistance. If resistance is persistent, the needle is likely in surrounding tissue and not within the tracheal lumen. If this is the case, remove the needle and re-direct. As the catheter is passed down the tracheal lumen, the dog may cough and may become slightly agitated. Once the catheter is in place, the needle is removed from the trachea. If it is a throughthe-needle catheter, place the guard over the needle. If a 16-gauge needle or an over-the-needle catheter was used, pull the needle back out of the trachea and over the catheter. Attach the preloaded syringe to the catheter and infuse the sterile saline into the trachea. It may be helpful to have an assistant perform coupage during instillation of the fluid so as to promote coughing. Aspirate the infused saline back into the syringe. If excess air is aspirated, the syringe may need to be detached from the catheter and the excess air expelled so as to aspirate as much fluid back as possible. It is common to recover only 10% or less of the infused volume. If desired, the procedure can be repeated with a second preloaded syringe. Once an adequate sample has been obtained, remove the syringe and catheter from the neck in a smooth motion. Place a soft, padded bandage over the catheter site for approximately 1 hour to minimize the formation of SQ emphysema.
Endotracheal Wash (ETW) ETW sampling is recommended in smaller patients (cats and dogs o10 kg) as their smaller tracheal lumen diameter precludes placement of a large needle between tracheal rings. ETW should also be considered in larger dogs that are fractious or resistant to
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restraint and in which performing a transtracheal wash could result in clinician or patient injury. General anesthesia is required for ETW and therefore may potentially result in more risk to the patient. Because anesthesia prevents a cough reflex, recovered fluid is more likely to represent large airway findings and therefore may be less diagnostic. With this technique, there is also more risk of contamination from the oropharynx Before anesthesia, preoxygenate the patient for 5-10 minutes. During this period of time, preload syringes with sterile, nonbacteriostatic 0.9% saline. Owing to the risk of bronchospasm during the procedure, bronchodilators are recommended in cats and may be considered in dogs with suspected inflammatory airway disease. Terbutaline (0.01 mg/kg SQ q 8 hours) can be administered 12-24 hours before the procedure, with the final dose given 2-4 hours before anesthetic induction. Owing to the inability to provide oxygen and inhalant anesthesia during the procedure, most patients are induced with injectable anesthetics such as propofol. These short-acting anesthetics also allow for quick recovery after the procedure. Similar to a TTW, aseptic technique should be followed for an endotracheal lavage. Place the patient in sternal or lateral recumbency with the affected side down. Carefully pass a sterile ET tube through the arytenoid cartilages into the trachea, taking care to avoid contaminating the tube with oropharyngeal secretions. Do not attach the anesthesia machine tubing to the ET tube until after the wash has been performed. Once the patient is intubated, feed a red rubber catheter (8 Fr) through the ET tube, being careful to maintain sterility. Attach a preloaded syringe to the catheter and infuse the contents through the catheter as previously described. The red rubber catheter may need to be shortened or a catheter adapter may need to be used to secure the syringe to the catheter. Aspirate the infused saline back into the syringe.
Bronchoscopy Endoscopic examination of the respiratory system is useful in the diagnosis of airway disease in dogs and cats. Tracheobronchoscopy should be considered in patients with acute or chronic cough, stridor, hemoptysis, or respiratory distress, when other diagnostics have not identified an underlying cause. Endoscopy allows for direct visualization of the lumen of larger airway and allows for sampling of cells, fluid, and infectious organisms from the airways by using BAL, bronchial brushing, or biopsy. Bronchoscopy is most helpful in patients with airway disease and may be less diagnostic in patients that have interstitial or isolated focal parenchymal pulmonary lesions. Equipment Both rigid and flexible endoscopes can be used to examine the respiratory system. Descriptions of equipment available for use in veterinary tracheobronchoscopy have been discussed elsewhere.3,4 Briefly, the use of rigid scopes is more limited but allows examination of the larynx, trachea, and carina. A flexible endoscope is required for examination of the segmental bronchi. The bronchoscope should contain an instrument channel (for biopsy and brush forceps and to obtain BAL samples), suction, and a light source and have the ability to perform bilateral tip deflection to direct the scope into appropriate airways. Anesthesia General anesthesia is required to perform bronchoscopy. All patients should be preoxygenated for at least 5-10 minutes before
anesthesia induction. Bronchodilator therapy as previously mentioned is recommended in feline patients before bronchoscopy, BAL, and ETW. Inhalant anesthesia is almost always utilized except in cats and very small dogs. In these patients, endotracheal intubation is not possible, as the bronchoscope would not fit through a small ET tube. In those patients, injectable propofol anesthesia is titrated to effect. A small diameter polypropylene catheter can be passed down the trachea to provide oxygen. Alternatively, some clinicians prefer to provide oxygen via jet ventilation or through the working channel of the scope.5-7 It is important to realize that the tracheal lumen may be completely occluded by the bronchoscope in small patients and hypoxia and hypercapnia may occur. It is recommended to perform airway examination and diagnostic sampling at several brief periods in these patients. The use of topical lidocaine and sterile lubricant can be used to prevent laryngospasm and arytenoid trauma as the scope is passed through the larynx multiple times. In patients that are large enough to allow inhalant anesthesia, place a sterile ET tube and take care to not contaminate the tube with oropharyngeal secretions during placement. A sterile Y- or T-shaped ET tube adapter can be used to allow passage of the endoscope into the ET tube while simultaneously allowing for oxygen and gas anesthesia delivery. Use a mouth gag to protect the bronchoscope from trauma in the unforeseen event of the patient awakening because of an insufficient plane of anesthesia. Anatomy Canine tracheobronchial anatomy has been well described and a systematic nomenclature scheme has been developed8 (Fig 1). The anatomy of the cat is not as well described, but most clinicians use the same nomenclature in this species although differences do exist. The use of a standardized nomenclature scheme helps clinicians describe the location of airway sampling or of lesions accurately and serves as a map that helps keep the operator aware of the scope's location in the airways throughout the procedure. The airways branch quickly and it is easy to become lost. If this happens, it is helpful to return the scope to the carina to orient the operator to location and then go directly back to the area of interest. Procedure Pass the bronchoscope either through the ET tube in larger patients or directly through the larynx in small patients as noted earlier. It is important to realize that the tracheobronchial airways are rigid and undue force with the scope can damage the airway mucosa resulting in hemorrhage or even tearing of the airway wall. For this reason, advance the scope carefully without force. First examine the trachea, then the carina. Next, evaluate the bronchi in a systemic consistent manner. The author examines the right mainstem bronchus first, following the segmental bronchi into the right cranial lobe until the scope reaches its limit. Next, return the scope to the carina for orientation and then examine the segmental bronchi of the right middle lobe. Repeat these steps until all lung lobes have been examined. Complete the visual examination before performing any sampling procedures. Normal tracheobronchial mucosa is smooth and pink with minimal secretions (Fig 2). Erythema indicates inflammation and excessive mucus can be seen with many inflammatory conditions such as bronchitis. Yellow or greenish mucopurulent exudate may be seen in cases of pneumonia or eosinophilic pneumonopathy9 (Fig 3). The trachea should be round and patent with easily visible tracheal rings. Tracheal collapse can be identified and the extent of lumen occlusion used to classify the grade of collapse10 (Fig 4). The dorsal tracheal membrane can be visualized as a narrow band of tissue. It should be tightly adhered to the dorsal tracheal wall and
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Fig. 1. Bronchoscopic anatomy of the dog. (From Amis TC, McKiernan BC. Systematic identification of endobronchial anatomy during bronchoscopy in the dog. Am J Vet Res 1986;47(12):2655; with permission.)
should not droop or occlude the lumen in any way. The carina should be a sharply demarcated division into right and left mainstem bronchi. Edema and inflammation can cause widening of the carina and narrowing or irregularity of the airway lumen. Bronchi should always be round, patent during all phases of respiration and well defined. Bronchomalacia, weakness of the bronchi that results in collapse of the airway during respiration, is often seen in conjunction with tracheal collapse11,12 (Fig 5). Bronchiectasis, abnormal dilation of the bronchi, may be seen secondary to chronic inflammatory disorders such as chronic bronchitis or eosinophilic pneumonopathy and can also be secondary to congenital anatomic defects13 (Fig 6). Pulmonary submucosal vessels are easily visualized and should not be enlarged, distended, or tortuous.3,7,14 Tracheal foreign bodies and tumors may also be visualized (Figs 7 and 8). When abnormalities are noted, record their location, severity, and description. Take digital photographs of any area of interest.
Fig. 2. Normal canine carina.
Digital videography can be used to document dynamic lesions such as tracheal or bronchial collapse. Once the visual examination is complete, sampling of the airways via BAL can be performed.
BAL BAL should always be performed after a thorough and systematic examination of the airways. After bronchoscopic examination of the lung lobes, the endoscope should be removed from the airways and the biopsy channel flushed with sterile saline. The scope can also be wiped down with sterile saline at this time. To get a representative sample, an adequate volume of fluid must be infused. The proper amount of saline to be infused is controversial with many different published recommendations. Both weightadjusted and fixed amounts of BAL volumes have been suggested.
Fig. 3. Thick greenish exudate in a canine patient with chronic bronchopneumonia. Notice the irregular proliferation of the bronchial wall.
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Fig. 4. Tracheal collapse in a dog.
Fig. 6. Severe bronchiectasis in a canine patient with chronic bronchitis.
For dogs, aliquots of 15-25 mL per wash have been recommended.1,14-16 In cats, owing to their smaller lung volume, aliquots of 3-10 mL per site are used.6,16,17 Other authors recommend choosing aliquot volumes based upon body weight. In dogs, a volume of 1 mL/kg per aliquot is usually recommended whereas in cats, 3-5 mL/kg is used.15,18,19 A recent study investigated the use of fixed-amount BAL compared with volumes based upon body weight. This study found that choosing volume on an milliliter per kilogram basis resulted in more uniform recovery of BAL fluid.15 Regardless of volume chosen, most authors recommend performing at least 2 washes at each site. The number of sites sampled depends on the patient's underlying disease. For patients with diffuse lung disease, at least 2 different lung lobes should be sampled. For patients with very focal disease (such as aspiration pneumonia), it may be necessary to perform a BAL only on the affected lung lobe. To perform a BAL, pass the endoscope through the airways into the smallest bronchus that will accommodate it, then gently wedge it in place as distally as possible. A tight fit of the scope in the bronchus is essential to facilitate retrieval of infused saline. Once the bronchoscope is wedged in place, attach a syringe preloaded with sterile nonbacteriostatic saline, as previously described, to the biopsy channel of the scope. It may be helpful to follow the saline infusion with 3-5 mL of air to make sure all fluid reaches the lung lobe. Retrieve the infused saline through the biopsy channel by gentle suction using the same syringe. The syringe can be detached
from the biopsy channel port and air expelled so that as much fluid as possible can be recovered. Ideally, retrieval of BAL fluid should be done with the scope in the same wedged position to regain as much fluid as possible. If no saline is retrieved, it may be because of airway collapse and less suction should be applied to the syringe. If negative pressure is still present, the scope can be pulled back a few millimeters but in this case, the volume of recovered fluid may be less. The use of vacuum suction and a specimen trap container has also been reported.7 The sample of retrieved BAL fluid should contain a layer of foamy surfactant that rises to the top of the fluid. The presence of surfactant is an indicator that the sample was obtained from the lower airways. Another indicator of a good BAL sample is recovery of approximately 50% of the infused saline. In dogs, median recoveries of 42%-48% of the infused saline have been reported.1,20 In cats, retrieval of 50%-75% of BAL fluid was reported in a retrospective study of 68 cats.19 Samples obtained via BAL should be placed on ice while further washes are being performed until the samples can be processed.
Fig. 5. Expiratory collapse of a lobar bronchus in a dog with bronchomalacia secondary to chronic bronchitis.
Fig. 7. A foreign body in the trachea of a dog. This rock was successfully removed using a retrieval device.
Complications of Lavage or Wash Procedures Following any airway wash procedures, all patients should receive supplemental oxygen via ET tube. Arterial oxygen tension
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Table Reported Total and Differential Cell Counts from Healthy Dogs and Cats Canine BAL Normals28 Total cell count (per μL) Neutrophils (%) Macrophages (%) Lymphocytes (%) Eosinophils (%)
Fig. 8. A tracheal mass almost completely obstructing the lumen of a cat's trachea. The mass was successfully debulked and histology demonstrated a carcinoma.
(PaO2) and oxygen saturation may be transiently decreased in healthy patients after BAL. Patients that are already affected with respiratory compromise may be more susceptible to decreases in pulmonary function. After 5 minutes, attempt to wean the patient off of supplemental oxygen. If cyanosis or decreases in oxygen saturation are noted, further oxygen supplementation is necessary. If the patient is recovering from anesthesia, it may be acceptable to continue oxygen supplementation via facial mask or oxygen cage. If the patient cannot be weaned off of supplemental oxygen, other causes such as bronchospasm or pneumothorax should be considered. Both injectable and inhaled bronchodilators have been used after BAL to alleviate bronchospasm.21 Tracheal laceration, SQ emphysema, and pneumomediastinum have been reported after TTW.2 It is also possible to sever the catheter during a TTW, which could result in a tracheal or bronchial foreign body. Transient worsening of respiratory distress or cough can occur after any lavage procedure. Spontaneous pneumothorax has been rarely reported after BAL.19 Rarely, complications from BAL may be fatal. In a retrospective study at a referral institution, 2 of 101 (2%) dogs died after BAL.1 Both of these patients were in respiratory distress before the procedure. In a retrospective study of cats, 4 of 68 cats (6%) were euthanized after BAL owing to an inability to restore adequate oxygenation and ventilation after the procedure.19
Fluid Analysis For best results, processing of TTW, ETW, and BAL samples should be performed within 1 hour of collection. When assessing cytology, lavage samples from each lobe should be assessed separately. In one study, 37% of dogs had differing results when samples from various lung lobes were evaluated.1 Total nucleated cell counts can be performed using a hemocytometer. Differences in technique and concentration of recovered fluid make normal total cell counts from BAL controversial. Because all wash samples are very dilute, cytocentrifugation techniques are recommended to concentrate the sample and increase the ease of assessing cytologic morphology and performing differential cell counts. Differential cell counts should be performed on every sample. A minimum of 200 cells should be counted, and one study suggested that more reproducible results can be reached if 500 cells are counted.18 The most common cell type recovered in BAL is the alveolar macrophage (4 70% in both dogs and cats).5,6,20 Cats normally contain higher numbers of eosinophils in BAL fluid than
200 5 70 7 6
7 7 7 7 7
86 5 11 5 5
Feline BAL Normals5,6 337 5 78 1 16
7 7 7 7 7
194 5 15 1 14
other species5,6 (Table). In contrast, the most common cell type in ETW and TTW is the neutrophil as the sample is from the larger airways and alveoli are not sampled.4 Samples obtained via ETW should always be evaluated for evidence of oropharyngeal contamination such as Simonsiella organisms. Interestingly, in a study of dogs with respiratory disease, almost half of the dogs had different categories of inflammation or a different diagnosis was reached when BAL and TTW fluid was compared. In half of the dogs (5/10), the bacterial culture was positive on BAL but negative on TTW. Overall, the diagnosis was different in 68% of the dogs.1 This suggests that for lower airway disease, BAL is superior to sampling via TTW. In dogs with spontaneous respiratory disease, neutrophilic or mixed inflammation is the most common abnormality found. Most dogs with bacterial infection have neutrophilic inflammation. Intracellular bacteria may be found.1 In dogs with chronic bronchitis, a mixed inflammatory or neutrophilic inflammation is seen most commonly. Increased numbers of eosinophils (20% to 4 50%) are seen in dogs with eosinophilic bronchopneumopathy.9 Activated macrophages may contain phagocytized organisms or red blood cells. Mixed inflammation is often seen with fungal infections. The presence of fungal organisms should be considered diagnostic. Differential cell counts can also be helpful in cats with lower airway disease. Neutrophilic inflammation with or without the presence of intracellular bacteria may be observed in cats with pneumonia. Cats with bronchitis or asthma often have an increased population of eosinophils. However, neutrophilic and eosinophilic inflammation is not pathognomonic for an infectious or immune-mediated process, as both eosinophilic and neutrophilic inflammation can also be observed with neoplasia.17 It can be difficult to reach a diagnosis of neoplasia from a sample obtained via BAL. All cells should be examined for criteria of malignancy. In the presence of concurrent inflammation however, care should be taken when interpreting malignancy. In a small study, cats with histologically diagnosed carcinoma showed neutrophilic inflammation but no evidence of cancer on cytology of fluid obtained via BAL.22 Another study showed considerable overlap of differential cell counts in cats with pneumonia, bronchitis, or neoplasia.17 Because of this, BAL cell counts should always be interpreted in combination with clinical signs and radiographic and bronchoscopic findings. Cultures The respiratory tree of normal healthy dogs is not sterile. Oropharyngeal contamination can result in false-positive results of any airway sample. Quantitative bacterial cultures may help to differentiate between contamination and true airway infections. More than 1.7 103 colony-forming units per milliliter obtained by quantitative bacterial culture has been shown to be sensitive and specific for bacterial bronchopneumonia.23 Aerobic and mycoplasma cultures should be performed on all airway samples.24 Fungal cultures may also be recommended in endemic areas. Fungal antigen testing has also been performed on BAL samples to diagnose histoplasmosis and blastomycosis in dogs. However,
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sensitivity is greater with serum or urine antigen testing for these diseases.25 In humans, coccidioidomycosis antigen testing can be performed on BAL samples. However, in dogs, sensitivity of antigen testing for coccidioidomycosis is poor at less than 20% and is not recommended. Polymerase Chain Reaction (PCR) Molecular diagnostics including PCR are an area of great interest in the diagnosis of many small-animal infectious diseases. The use of PCR on airway wash samples has been reported to diagnose Mycoplasma species, Bordetella bronchiseptica, and Toxoplasma gondii.24,26,27 PCR results should be interpreted with caution. Organisms such as Mycoplasma and Bartonella can be normal inhabitants of the oropharynx of dogs and cats. Therefore, a positive result does not guarantee that the pathogen is causing the patient's current clinical signs. In addition, a negative result does not rule out infection. Although the organism may be present in the airways, it may not be present in the small sample used for DNA extraction, resulting in a false-negative test.
Conclusion Respiratory airway disease can be a diagnostic challenge. Although history, physical examination, and thoracic radiographs often help clinicians reach a diagnosis, occasionally further diagnostics are necessary. In patients with airway disease, visualization of the airways can be a powerful diagnostic tool. Sampling the airways via TTW or BAL allows for cytologic and culture analysis of airway secretions. These modalities may allow for confirmation of chronic inflammatory conditions or allow for identification of infectious organisms. The diagnostic value of these tests cannot be overemphasized. Because patients with airway disease have increased risks with anesthesia and respiratory procedures, the risk of the procedure should always be weighed against the value of the expected results. References 1. Hawkins EC, DeNicola DB, Plier ML. Cytologic analysis of bronchoalveolar lavage fluid in the diagnosis of spontaneous respiratory tract disease in dogs: a retrospective study. J Vet Intern Med 9:386–392, 1995 2. Syring RS. Tracheal washes. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 128–134 3. Kuehn NF, Hess RS. Bronchoscopy. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 112–118 4. McKiernan BC. Bronchoscopy. In: McCarthy TC, editor. Veterinary Endoscopy for the Small Animal Practitioner. St. Louis: Elsevier Saunders; 2005. p. 201–227
5. Hawkins EC, Kennedy-Stoskopf S, Levy J, et al. Cytologic characterization of bronchoalveolar lavage fluid collected through an endotracheal tube in cats. Am J Vet Res 55:795–802, 1994 6. Padrid PA, Feldman BF, Funk K, Samitz EM, Reil D, C.E. Cross. Cytologic, microbiologic, and biochemical analysis of bronchoalveolar lavage fluid obtained from 24 healthy cats. Am J Vet Res 52:1300–1307, 1991 7. Creevy KE. Airway evaluation and flexible endoscopic procedures in dogs and cats: laryngoscopy, transtracheal wash, tracheobronchoscopy, bronchoalveolar lavage. Vet Clin Small Anim 39:869–880, 2009 8. Amis TC, McKiernan BC. Systemic identification of endobronchial anatomy during bronchoscopy in the dog. Am J Vet Res 47:2649–2657, 1986 9. Clercx C, Peeters D, Snaps F, et al. Eosinophilic bronchopneumopathy in dogs. J Vet Intern Med 14:282–291, 2000 10. Mason RA, Johnson LR. Tracheal collapse. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 346–355 11. Adamama-Moraitou KK, Pardali D, Day MJ, et al. Canine bronchomalacia: a clinicopathological study of 18 cases diagnosed by endoscopy. Vet J 191: 261–266, 2010 12. Johnson LR, Pollard RE. Tracheal collapse and bronchomalacia in dogs: 58 cases (7/2001-1/2008). J Vet Intern Med 24:298–305, 2010 13. Norris CR. Bronchiectasis. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 376–379 14. Mercier E, Bolognin M, Hoffmann AC, Tual C, Day MJ, Clercx C. Influence of age on bronchoscopic findings in healthy beagle dogs. Vet J 187:225–228, 2011 15. Melamies MA, Jarvinen AK, Seppala KM, Rita HJ, Rajamaki MM. Comparison of results for weight-adjusted and fixed-amount bronchoalveolar lavage techniques in healthy Beagles. Am J Vet Res 72:694–698, 2011 16. Dehard S, Bernaerts F, Peeters D, et al. Comparison of bronchoalveolar lavage cytospins and smears in dogs and cats. J Am Anim Hosp Assoc 44: 285–294, 2008 17. Johnson LR, Vernau W. Bronchoscopic findings of 48 cats with spontaneous lower respiratory tract disease (2002-2009). J Vet Intern Med 25:236–243, 2011 18. De Lorenzi D, Masserdotti C, Bertoncello D, Tranquillo V. Differential cell counts in canine cytocentrifuged bronchoalveolar lavage fluid: a study on reliable enumeration of each cell type. Vet Clin Pathol 38:532–536, 2009 19. Johnson LR, Drazenovich TL. Flexible bronchoscopy and bronchoalveolar lavage in 68 cats (2001-2006). J Vet Intern Med 21:219–225, 2007 20. Hawkins EC, Rogala AR, Large EE, Bradley JM, Grindem CB. Cellular composition of bronchial brushings obtained from healthy dogs and dogs with chronic cough and cytologic composition of bronchoalveolar lavage fluid obtained from dogs with chronic cough. Am J Vet Res 67:160–167, 2006 21. Kirschvink N, Leemans J, Delvaux F, Snaps F, Clercx C, Gustin P. Bronchodilators in bronchoscopy-induced airflow limitation in allergen-sensitized cats. J Vet Intern Med 19:161–167, 2005 22. Norris CR, Griffey SM, Samii VF, Christopher MM, Mellema MS. Thoracic radiography, bronchoalveolar lavage cytopathology, and pulmonary parenchymal histopathology: a comparison of diagnostic results in 11 cats. J Am Anim Hosp Assoc 38:337–345, 2002 23. Peeters DE, McKiernan BC, Weisiger RM, Schaeffer DJ, Clercx C. Quantitative bacterial cultures and cytological examination of bronchoalveolar lavage specimens in dogs. J Vet Intern Med 14:534–541, 2000 24. Chalker VJ, Owen WM, Paterson C, et al. Mycoplasmas associated with canine infectious respiratory disease. Microbiology 150:3491–3497, 2004 25. Spector D, Wheat J, Beamis D, Rohrbach B, Taboada T, Legendre AM. Antigen testing for the diagnosis of Blastomycosis. J Vet Intern Med 20:711–712, 2006 26. Egberink H, Addie D, Belak S, et al. Bordetella bronchiseptica infections in cats. J Fel Med Surg 11:610–614, 2009 27. Anfray P, Bonetti C, Fabbrini F, Magnino S, Mancianti F, Abramo F. Feline cutaneous toxoplasmosis: a case report. Vet Dermat 16:131–136, 2005 28. Hawkins EC. Bronchoalveolar lavage. In: King LG, editor. Textbook of Respiratory Disease in Dogs and Cats. St. Louis: WB Saunders; 2004. p. 118–128
