Page 314 - Small Animal Internal Medicine, 6th Edition

286 PART II Respiratory System Disorders

but are common in patients with pulmonary edema or pneu- mass lesion), the degree of respiratory compromise of the
monia. Crackles are nonmusical, discontinuous noises that patient, and the client’s motivation for optimal care.
VetBooks.ir sound like paper being crumpled or bubbles popping. Dis- tests have the obvious advantage of being nearly risk free but
Invasive and noninvasive tests are available. Noninvasive
eases resulting in the formation of edema or an exudate
within the airways (e.g., pulmonary edema, infectious or
with persistent lower respiratory tract disease often require
aspiration pneumonia, bronchitis) and some interstitial are usually aimed at confirming a specific diagnosis. Patients
pneumonias, particularly interstitial fibrosis, can result in collection of a pulmonary specimen for microscopic and
crackles. Wheezes are musical, continuous sounds that indi- microbiologic analysis to further narrow the list of differen-
cate the presence of airway narrowing. Narrowing can occur tial diagnoses or to make a definitive diagnosis. Although the
as a result of bronchoconstriction, bronchial wall thickening, procedures for specimen collection from the lung are consid-
exudate or fluid within the bronchial lumen, intraluminal ered invasive, they carry varying degrees of risk, depending
masses, or external airway compression. Wheezes are most on the procedure used and the degree of respiratory compro-
commonly heard in cats with bronchitis. Wheezes caused by mise of the patient. The risk is minimal in many instances.
an intrathoracic airway obstruction are loudest during early Noninvasive tests include serology, urine antigen tests,
expiration. Sudden snapping at the end of expiration can and polymerase chain reaction (PCR) tests for pulmonary
be heard in some dogs with intrathoracic tracheal collapse. pathogens, fecal examinations for parasites, and specialized
imaging techniques such as fluoroscopy, angiography, com-
Radiography puted tomography (CT), ultrasonography, magnetic reso-
Thoracic radiographs are indicated in dogs and cats with nance imaging (MRI), and nuclear imaging. Techniques for
lower respiratory tract signs. Neck radiographs should also collection of pulmonary specimens that can be performed
be obtained in animals with suspected tracheal disease. without specialized equipment include tracheal wash, non-
Radiography is perhaps the single most helpful diagnostic bronchoscopic bronchoalveolar lavage, and transthoracic
tool in the evaluation of dogs and cats with intrathoracic lung aspiration. Visually guided specimens can be collected
disease. It helps in localizing the problem to an organ system during bronchoscopy. Bronchoscopy offers the additional
(i.e., cardiac, pulmonary, mediastinal, pleural), identifying benefit of allowing visual assessment of the airways. If analy-
the area of involvement within the lower respiratory tract sis of lung specimens and results of reasonable noninvasive
(i.e., vascular, bronchial, alveolar, interstitial), and narrowing tests do not provide a diagnosis in a patient with progressive
the list of potential differential diagnoses. It also helps in the disease, thoracoscopy or thoracotomy with lung biopsy is
formulation of a diagnostic plan (see Chapter 20). Additional indicated.
diagnostic tests are necessary in most animals to establish a Valuable information about patients with lower respira-
definitive diagnosis. tory tract disease can also be obtained by assessing lung
function through arterial blood gas analysis. Results are
Complete Blood Count rarely helpful in making a final diagnosis, but they are useful
The CBC of patients with lower respiratory tract disease may in determining degree of compromise and in monitoring
show anemia of inflammatory disease, polycythemia sec- response to therapy. Pulse oximetry, a noninvasive technique
ondary to chronic hypoxia, or a white blood cell response used to measure oxygen saturation of the blood, is particu-
characteristic of an inflammatory process of the lungs. The larly valuable in monitoring patients with respiratory com-
hematologic changes are insensitive, however, and an absence promise during anesthetic procedures or respiratory crises.
of abnormalities cannot be used as the basis for ruling out
inflammatory lung disease. For instance, only half of dogs Suggested Readings
with bacterial pneumonia have a neutrophilic leukocytosis Bohadan A, et al. Fundamentals of lung auscultation. N Engl J Med.
and a left shift. 2014;370:744.
Ferasin L, et al. Risk factors for coughing in dogs with naturally
PULMONARY SPECIMENS AND SPECIFIC acquired myxomatous mitral valve disease. J Vet Intern Med.
DISEASE TESTING 2013;27:286.
On the basis of results of the history, physical examination, Hamlin RL. Physical examination of the pulmonary system. Vet
Clin N Am Small Anim Pract. 2000;30:1175.
thoracic radiographs, and CBC, a prioritized list of differen- Hawkins EC, et al. Demographic and historical findings, including
tial diagnoses is developed. Additional diagnostic tests (Fig. exposure to environmental tobacco smoke, in dogs with chronic
19.1) are nearly always required to achieve a definitive diag- cough. J Vet Intern Med. 2010;24:825.
nosis, which is necessary for optimal therapy and outcome. Sarkar M, et al. Ausculation of the respiratory system. Ann Thor
Selection of appropriate tests is based on the most likely Med. 2015;10:158.
differential diagnoses, the localization of disease within the Singh MK, et al. Bronchomalacia in dogs with myxomatous mitral
lower respiratory tract (e.g., diffuse bronchial disease, single valve degeneration. J Vet Intern Med. 2012;26:312.