Page 310 - Small Animal Internal Medicine, 6th Edition

282 PART II Respiratory System Disorders

CHAPTER 19
VetBooks.ir

Clinical Manifestations

of Lower Respiratory

Tract Disorders

CLINICAL SIGNS not hearing or seeing evidence of productivity does not rule out
the possibility of its presence, and these differentials should
In this discussion, the term lower respiratory tract disorders remain under consideration.
refers to diseases of the trachea, bronchi, bronchioles, alveoli, Productive coughs are most commonly caused by inflam-
interstitium, and vasculature of the lung (Box 19.1). Dogs matory or infectious diseases involving the airways or alveoli
and cats with diseases of the lower respiratory tract are com- and by heart failure. A moist sound can often be heard
monly seen for evaluation of cough. Lower respiratory tract during the cough. Animals rarely expectorate the fluid, but
diseases that interfere with the oxygenation of blood can swallowing can often be seen after a coughing episode. If
result in respiratory distress, exercise intolerance, weakness, expectoration occurs, clients may confuse the cough with
cyanosis, or syncope. Nonlocalizing signs such as fever, vomiting. Cough in cats can be confused with attempts to
anorexia, weight loss, and depression also occur and are the vomit a hairball. Cats that never produce a hairball are likely
only presenting sign in some animals. Auscultation and tho- coughing (Video 19.1).
racic radiography help localize the disease to the lower respi- Hemoptysis is the coughing up of blood. Blood-tinged
ratory tract in these animals. The two major presenting signs saliva may be observed within the oral cavity or dripping
in animals with lower respiratory tract disease—cough and from the commissures of the mouth after a cough. Hemop-
respiratory distress—can be further characterized by a tysis is an unusual clinical sign that most commonly occurs
careful history and physical examination. in animals with heartworm disease or pulmonary neoplasia.
Less common causes of hemoptysis are mycotic infection,
COUGH foreign bodies, severe congestive heart failure, thromboem-
A cough is an explosive release of air from the lungs through bolic disease, lung lobe torsion, and some systemic bleeding
the mouth. It is generally a protective reflex to expel material disorders, such as disseminated intravascular coagulation
from the airways, although inflammation or compression (see Box 19.2).
of the airways can also stimulate cough. Cough is some- Intensity of cough is useful in prioritizing the differential
times caused by disease outside of the lower respiratory diagnoses, although exceptions are common. Cough asso-
tract. Chylothorax and laryngeal disease can cause cough. ciated with airway inflammation (i.e., bronchitis) or large
Although not well documented in dogs or cats, gastroesoph- airway collapse is often loud, harsh, and paroxysmal. The
ageal reflux and postnasal drip are common causes of cough cough associated with tracheal collapse is often described as
in people. a “goose-honk.” Cough resulting from tracheal disease can
Classically in human medicine, differential diagnoses for usually be induced by palpation of the trachea, although
cough are divided into those that cause productive cough there is often concurrent involvement of the deeper airways.
and those that cause nonproductive cough. A productive Cough associated with pneumonias and pulmonary edema
cough results in the delivery of mucus, exudate, edema fluid, is often soft.
or blood from the airways into the oral cavity, whereas a The association of coughing with temporal events can be
nonproductive cough is a dry cough. This distinction is helpful. Cough resulting from tracheal disease is exacerbated
readily made in people because they can report their experi- by pressure on the neck, such as pulling on the animal’s
ence. However, in veterinary medicine, many patients with collar. Cough caused by heart failure tends to occur more
productive diseases do not appear to have a productive frequently at night, whereas cough caused by airway inflam-
cough, despite careful observation and auscultation. There- mation (bronchitis) tends to occur more frequently upon
fore, if a cough can be identified as productive the list of rising from sleep or during and after exercise or exposure to
differential diagnoses can be narrowed (Box 19.2). However, cold air. The client’s perception of frequency may be biased

282