Approach to the coughing dog

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DOI: 10.1136/inp.f5838
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Abstract
A wide variety of conditions can cause coughing in dogs, which can present either as an acute problem or a chronic condition. This article aims to provide a pragmatic review of coughing in dogs. An understanding of the location of the cough receptors in the respiratory tract is key to understanding how best to investigate coughing. It considers the pathophysiology of coughing and its diagnosis, offering tips on the more useful diagnostic tests for each condition.
Companion animalS
503
In Practice October 2013 | Volume 35 | 503-517
doi:10.1136/inp.f5838
A wide variety of conditions can cause coughing in dogs, which can present
either as an acute problem or a chronic condition. This article aims to provide
a pragmatic review of coughing in dogs. An understanding of the location of
the cough receptors in the respiratory tract is key to understanding how best
to investigate coughing. It considers the pathophysiology of coughing and its
diagnosis, offering tips on the more useful diagnostic tests for each condition.
Mike Martin is an RCVS
Specialist in Veterinary Cardiology.
He qualified from University
College Dublin in 1986. He has
been an examiner at certificate
and diploma level for the Royal
College of Veterinary Surgeons and
has been both Honorary Secretary
and Chairman of the Veterinary
Cardiovascular Society. He has
published over 40 scientific peer
reviewed papers and is the author
of two textbooks. He is a recipient
of BSAVA awards: the Dunkin
Award in 1993, the Melton Award
in 2000, the Petsavers Award in
2006 and the Dunkin and Blaine
Awards in 2010.
Approach to the coughing dog
Mike Martin, Yolanda Martinez Pereira
COUGHING is an imp ortant component of t he defence
mechanisms of the respiratory system. Its presence usu-
ally indicates an attempt to eliminate foreign materi-
al, secretions or irritants from the airways. However,
coughing can also be triggered by non-respiratory con-
ditions such as cardiac disease or anything that exerts
external pressure on the airways (Table 1).
Coughing can present as an acute problem, com-
monly associated with airway infection or aspiration of
foreign material. However, many patients will present
with ongoing, chronic coughing. Although this is not
usually a life-threatening clinical sign, it has a signifi-
cant impact on the quality of life of the patient and the
owner.
The therapeutic approach to coughing relies on
the formulation of an accurate diagnosis; however,
it is important to make sure there is a realistic under-
standing of the chances of a complete resolution of the
coughing from the owner. As an example, for a disease
such as chronic bronchitis only palliative treatment will
be available and complete resolution of the cough is
unlikely.
This article reviews the mechanisms involved in the
pathophysiology of coughing and its differential diag-
nosis. The aim is to provide a pragmatic review of the
more common causes of coughing in dogs. Tips on the
more useful diagnostic tests for each condition will be
provided with a brief overview of the typical treatment.
Pathophysiology of coughing
The defence strategies of the respiratory system are
based on exclusion of agents/particles from the res-
piratory mucosa and active elimination. Exclusion is
achieved by air filtration in the nose and the presence
of a lining of mucus containing antimicrobial sub-
stances. This is constantly produced by the mucous
glands of the respiratory mucosa (goblet cells and sub-
mucosa l glands) of the ‘conduc ting air ways’ (from nose
to terminal bronchioles). The respiratory epithelium is
also lined with cilia, which are in constant movement.
The movement of the cilia will transport the mucus
towards the larynx (caudal movement in the nasal
cavity, cranial movement in the trachea and lower air-
ways) where it can be degluted and then eliminated
from the respiratory system. Other mechanisms that
allow elimination of agents/particles are the coughing
and sneezing reflexes. Laryngeal closure, increased
mucus production and bronchoconstriction are addi-
tional defence mechanisms.
Cough ing is initiated by sti mulation of sensory ner ve
endings, cough receptors, which are located in the epi-
thelial lining of the caudal oropharynx, the larynx, the
trachea and the bronchial tree. Smaller distal airways
have lower concentrations of receptors, and respiratory
bronchioles and alveolae have none. Different types of
cough receptors have been described: some respond to
mechanical stimuli (such as the rapidly adapting stretch
or irritant mechanoreceptors) and others are more sen-
sitive to chemical stimuli (such as C fibre receptors).
Cough receptors send information through afferent
neural pathways to the cough receptor situated within
the brainstem. The efferent pathway then follows, elic-
iting a cough by triggering a deep inspiration, followed
by a compressive phase against a closed glottis (increas-
ing airway pressure) and then finally the sudden expul-
sive phase when the glottis opens.
The owner’s description of coughing
Veterinarians are familiar with coughing and the
expiration reflex and have no difficulty identify-
ing this. Trying to discern from owners whether the
coughing is the clinical sign can be challenging as
coughing is often misinterpreted with choking, gag-
ging, retching, gasping or throat clearing noise, for
example. It seems prudent, therefore, to include them
all, using ‘cough’ as an umbrella term for this eclectic
group of clinical signs. Additionally, the diagnostic
approach to all of these is similar. However, regurgi-
tation and vomiting are terms that can get confused
with coughing as well, but would generally involve
a different approach, necessitating a gastrointestinal
investigation instead. Coughing and retching can
Yolanda Martinez Pereira
obtained her degree in veterinary
medicine in 1998 in Spain. In
2004 she completed an internship
in cardiology, obtaining the
RCVS certificate in veterinary
cardiology. From 2005 to 2008
she completed a residency in
cardiopulmonary medicine at the
University of Edinburgh. During
2009 to 2012, she joined Borders
Veterinary Cardiology, providing a
mobile cardiology referral service
in Scotland. She returned to the
Royal (Dick) School for Veterinary
Studies in 2013 as a lecturer in
cardiopulmonary medicine.
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COMPANION ANIMALS
trigger regurgitation and vomiting, so it becomes
important to establish from the history if the vomit-
ing was preceded by coughing/retching.
Diagnostic approach to the coughing
patient
Breed
Breed predispositions are invaluable in formulating a
differential diagnosis and these will be covered in the
diseases described later.
Important points regarding history taking
Evaluate the nature of the coughing: acute, chron-
ic, recurrent, progressively worse, seasonal.
The owner might be able to describe the type of
cough, such as loud or honking, gagging, or soft.
If eating or drinking provokes the cough, it may
suggest that the cough is secondary to a pharyngeal
dysphagia +/ laryngeal paralysis.
If the cough is associated with excitement, it might
be suggestive of dynamic large airway collapse.
What is the severity of the coughing? It is impor-
tant to obtain a baseline so we can then assess the
respons e to treatment. For ex ample, is the coug hing
on a daily basis, several times a day, once a week? Is
it on exercise only? When pulling on a lead?
What is the main complaint? Are there other res-
piratory signs, such as dyspnoea, exercise intoler-
ance or nasal disease?
A patient with chronic coughing which is otherwise
well is more likely to suffer from inflammatory air-
way disease. A patient with cardiac cough is likely
to have a murmur and have other clinical signs such
as decreased exercise tolerance and tachypnoea.
Are other pets affected at home or in the neigh-
bourhood, suggesting a contagious disease? Or has
the dog been exposed to a population of other dogs
in kennels, agility classes or puppy classes?
Background – access to cigarette smoke, dust
(eg, recent refurbishing or building works), other
inhaled irritants, potential foreign bodies (FBs)
(eg, after running in a field).
Previous response to treatment – for example,
coughing that improves when injection for pruritic
skin disease is given is likely to have an inflamma-
tory background.
Is worming up to date or could the dog have had
exposure to lungworm?
Important points regarding physical
examination
Body cond ition: respirator y signs ca n be exacerbated
by obesity (eg, tracheal collapse), whereas cachexia
can be observed in some patients with neoplasia or
cardiac disease.
Heart rate and rhythm: presence of sinus arrhyth-
mia makes heart failure less likely and respiratory
disease more likely. Presence of tachycardia and
arrhythmias would suggest cardiac disease.
Abnormal cardiac sounds: a left-sided systolic mur-
mur should be present in dogs with mitral valve
disease (MVD). However, its presence does not nec-
essarily infer that there is heart failure; thus, further
diagnostic tests would be needed to determine this.
Abnormal respiratory sounds such as wheeze, pul-
monary crackles or laryngeal stridor.
Remember to auscultate not only the heart and lung
fields but also over the trachea and larynx, particu-
larly if there is an inspiratory or expiratory dysp-
noea, or abnormal airway sounds.
It is usually best to leave inducement of the cough to
the end of the physical examination. A cough origi-
nating from a large airway is typically loud, such as
Conditions Common Uncommon
Upper airway disorders Post nasal drip (purulent rhinitis)
BOAS with retching of saliva, aspiration
pneumonia
Laryngeal paralysis
Tracheal collapse
Kennel cough
Laryngeal neoplasia
Inflammatory laryngitis
Tracheal polyp
Oropharyngeal penetrating stick injuries
Primary ciliary dyskinesia
Lower airway and pulmonary parenchymal
diseases
Inhaled airway FB
Chronic bronchitis
Eosinophilic bronchopneumopathy
Bronchomalacia
Lungworm disease
Idiopathic pulmonary fibrosis
Aspiration pneumonia
Pulmonary neoplasia (primary or metastatic)
Non-cardiogenic oedema
Bronchiectasis
Lung lobe torsion
Pneumocystis pneumonia
Viral pneumonia
Pulmonary granuloma (eg, eosinophilic)
Pulmonary abscess
Pulmonary haemorrhage (warfarin poisoning)
Irritant gas inhalation
Trauma
Fungal pneumonia (rare in the British Isles)
Cardiac disease Left atrial dilation causing compression of the
left mainstem bronchus
Pulmonary oedema
Pericardial effusion
Heart base tumour
Pleural space disease Large mediastinal mass compressing airways
Large hilar lymph nodes compressing air ways
Pleural effusions
Pleuritis
Table 1: A differential list for the more common and some uncommon causes of coughing in dogs
BOAS Brachycephalic obstructive airway syndrome
Oesophageal disorders Megaoesophagus causing retching or
aspiration pneumonia
Gastro-oesophageal intussusception causing
retching or leading to aspiration
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Fig 1: Endoscopic view of the larynx of a labrador,
showing images taken during (a) expiration and
(b) inspiration. Note the lack of abduction of the
arytenoids during inspiration, in fact paradoxically the
vocal folds are sucked inwards during inspiration in
this instance
kennel cough or tracheal collapse. Coughing that is
softer is often associated with small airway disease,
such as bronchopneumonia.
Formulating a diagnostic plan
The findings from the h istory and physical exa mination
should help the practitioner to elaborate a list of differ-
ential diag noses, from mos t to least likely. It may well be
that a provi sional diagnosis is m ade at this point , such as
kennel cough, and treatment can be instigated without
need for further diagnostic tests. However, for dogs in
which the diagnosis is not clear, or wh ich fail to respond
to initial treatment, then a differential list needs to be
made and further investigations need to be considered.
In patients where no clear differentiation between
cough of cardiac or respiratory origin is evident, radio-
graphs are likely to be the most rewarding diagnostic
test. However, images of good diagnostic quality are
essential; otherwise the accuracy of radiographic inter-
pretation reduces significantly (Martin and Mahoney
2013). In situations where chest radiographs do not
clearly differentiate cardiac from respiratory causes of
cough ing, then a seru m NT-proBNP can be a u seful test.
Based on the laboratory reference ranges, the result falls
into three categories: high, low or mid-range (the grey
zone). A high result would be strongly indicative of the
presence of cardiomegaly and, therefore, heart disease
would be the likely cause of the coughing. A low result
would suggest there is not cardiomegaly and, therefore,
respiratory disease would be more likely. However, a
mid-range result would be inconclusive.
As a general rule, in patients showing signs of upper
respiratory disease (eg, laryngeal stridor, inspiratory
dyspnoea) orol aryngeal inspection u nder general anae s-
thesia should be undertaken. Further investigation in
patients with findings suggestive of cardiac disease
would include thoracic radiographs, echocardiography,
blood pressure measurement and electrocardiography.
In patients with findings suggestive of respiratory dis-
ease it would include thoracic radiographs, inspection
of the pharynx and larynx under general anaesthesia,
bronchoscopy and airway cytology with culture.
Common conditions that cause
coughing in dogs
Upper airway disorders
Nasal disease
A purulent nasal discharge can result in the discharge
trickling to the pharynx and triggering a cough, some-
times referred to as a ‘post-nasal drip’. In the majority of
these cases t he nasal discharge is also evident at t he nares
along wit h other nasa l signs and na sal disea se can reas on-
ably be assumed to be the cause of the cough. However,
it would be prudent to obtain chest radiographs and per-
form bronchoscopy to screen for lower airway disease.
Brachycephalic obstructive airway syndrome
(BOAS)
In this condition there may be a combination of airway
deformities, typically narrowed nares, overlong and/or
fat soft palate, hypoplastic trachea and possibly swollen
or prolapsed laryngeal saccules. BOAS predominately
results in inspiratory stertor and inspiratory dyspnoea.
However, many dogs also tend to regurgitate or retch
copious volumes of saliva that have accumulated in the
oesopha gus; this i s particu larly seen in bul ldogs. Some of
these dogs may have concurrent gast ric irritat ion or even
a hiatal hernia that contributes to the saliva accumula-
tion. In some, the saliva, or even food, can be aspirated
leading to a ventral pneumonia or air way irritation, trig-
gering coughing. Non-cardiogenic pulmonary oedema
can also be triggered by acute and severe episodes of
dyspnoea from the upper airway obstruction.
Laryngeal paralysis
Laryngeal paralysis usually affects older dogs of large
breeds (labrador, setter, etc) and may also present with
a history of decreased exercise tolerance and coughing.
The coug hing may someti mes be more of a gag, or th roat
clearing type noise. It may be triggered by aspiration of
saliva into the glottis or mucosal inflammation around
the rima glottis (Fig 1). In some dogs, there may also be
aspiration when eating or drinking. There is usually a
change in tone of the bark (if the dog barks) and they
usually have a degree of inspiratory dyspnoea with an
increased and prolonged airway noise (stridor) on aus-
cultation over the larynx/trachea. The clinical signs
can be exacerbated by heat or exercising on warm days,
(a)
(b)
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often with cyanosis. The diagnosis requires laryngos-
copy (in sternal recumbency) under a very light plane of
anaesthesia, such that the swallowing reflex is still pre-
sent. Timing with breathing is critical to the diagnosis.
In the normal dog, there should be active abduction of
the arytenoids (opening of the glottis) during inspira-
tion; failure to do so is indicative of paralysis. However,
mistiming can result in misdiagnosis. Laryngeal paraly-
sis can be surgically managed with a tie-back procedure
for those in which there is a significant inspiratory dysp-
noea or stridor. There are a few dogs in which laryngeal
paralysis cannot be surgically managed; initially, these
dogs typically present with a gag/cough and laryngeal
inf lammation , without strid or. The cau se of this aty pical
presentation is unclear, but it might be associated with
a polyneuropathy in some cases; in these cases surgery
is ineffectual. In some of these dogs, concurrent aspi-
ration pneumonia may be present and detected on tho-
racic radiographs. A barium swallowing study (which
requires fluoroscopic image intensification) might be
needed to screen for swallowing problems (as part of the
polyneuropathy) or for aspiration. This should be per-
formed with care in dogs that are dysphagic.
Tracheal collapse
Tracheal collapse affects small breed dogs (eg,
Yorkshire terrier), which present with chronic, ‘honk-
ing’ coughing exacerbated by excitement. The cough-
ing is easily induced by gentle tracheal palpation and
is a loud cough (large airway cough). A radiographic
diagnosis alone is often insufficient, requiring an ele-
ment of luck in recording the movement of the trachea,
with both inspiratory and expiratory views required.
Bronchoscopy (Fig 2) and/or fluoroscopy (Fig 3) are
much more useful in assessment of a moving structure
such as tracheal collapse. Four degrees of severity are
described and the disease is progressive in nature.
Weight loss and avoidance of collars are an important
part of the medical management of the condition. A
tracheal stent can be implanted in patients with severe
obstructive airway disease that is causing life threaten-
ing dyspnoea (this requires fluoroscopic image inten-
sification). However, dogs will continue to cough and
so cough alone is not an indication for this technique.
Bronchomalacia
Bronchomalacia refers to narrowing or collapse (usual-
ly dynamic) of the principal bronchi and/or lobar bron-
chi associated with weakness in the airway walls. Many
dogs with tracheal collapse (see above) also have bron-
chomalacia and this i s referred to as tracheobronchoma-
lacia (TBM). But some dogs can have bronchomalacia
without tracheal collapse and not all cases seen are of
toy breeds. T here is a high prevalence of air way collapse
in brachycephalic breeds. TBM is often concurrently
present with lower airway diseases (described later)
and has similar clinical signs. The airway collapse trig-
gers chronic and often severe coughing, which in itself
triggers airway inflammation. Breaking the cycle is key
to easing clinical signs by decreasing inhaled environ-
mental irritants, providing bronchodilators and reduc-
ing inflammation with corticosteroids. Additionally,
concurrent respiratory disease and obesity needs to be
addressed. Cough suppressants can also be helpful in
some cases to break the cough-inflammation cycle.
Kennel cough (infectious tracheobronchitis)
Kennel coug h produces a characteristic loud and harsh
cough, but it is a self-limiting disease. However, some
patients may present with chronic coughing (eg, with
Bordetella bronchiseptica infections). Younger dogs
and patients exposed to dog communities are predis-
posed, as this is a highly contagious condition.
Lower airway and pulmonary
parenchymal diseases
Airway foreign body
This condition causes acute onset coughing that can
mimic kennel cough. The cough can seem to abate with
empirical treatment, but then leads to a localised bron-
chopneumonia and rec urrence of the coug h some weeks
later, when halitosis may become a prominent clinical
sign. In dogs, a variety of FBs can be inhaled, such as
twigs and small stones; however, airway FBs are usu-
ally associated with running through dry crop fields,
typically towards the end of summer or early autumn.
These airway FBs are typically lodged in a large bron-
chus directly in line with the trachea, typically situated
within the left or right caudal lobe segmental bronchus
(Fig 4). The FB is often difficult to see on radiography,
Fig 3: An image from a fluoroscopic examination in a
conscious Jack Russell terrier restrained in right lateral
recumbency (head to the left, spine to top) showing
collapse of the trachea on (a) inspiration (white arrows)
and then dilation on (b) expiration (black arrows)
Fig 2: Endoscopic view of the cer vical trachea in a
Yorkshire terrier showing dorsoventral flattening of
the cervical trachea, consistent with tracheal collapse
(a)
(b)
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but the progression to a lobar pneumonia would be radi-
ographically evident. Bronchoscopy is essential in these
case s, not only for visualis ation of the FB (Fig 5) but a lso
for retrieval. In experienced hands, the vast majority of
FBs can be removed with endoscopic visualisation and
appropriate endoscopic instruments. Surgery would
rarely be needed for this condition. Very small grass
seeds will become lodged in very small airways, which
an endoscope cannot reach; these can migrate through
the lung tissue and into the pleural space, leading to a
pyothorax, pneumothorax or an abscess in dogs.
Chronic bronchitis
Chronic bronchitis usually affects middle aged to older
dogs and is defined as daily coughing of more than two
months duration. In some patients, abnormal respirato-
ry sounds can be auscultated, such as expiratory wheeze
and pulmonar y crackles, but i n others, lung aus cultation
can be unremarkable. Dogs often present with an expir-
atory dyspnoea and end-expiratory abdominal heave.
Radiographic abnormalities (ie, the intensity of a bron-
chial pattern) do not always correlate with the degree
of inflammation (Fig 6). Bronchoscopic examination
often reveals a widespread mucoid airway discharge,
mucosal thickening and irregularity and narrowing of
smaller bronchi (Fig 7). Bronchoalveolar lavage (BAL)
is useful to assess the airway cell response and search
for evidence of any infection. Palliative treatment is usu-
ally offered with a combination of steroids (oral and/or
inhaled), bronchodilators, antibiotics, nebulisation and
weight loss. Treatment is usually necessary for several
weeks and many patients will require life-long treat-
ment. Complete resolution of the cough is rare, but con-
trol to a tolerable level is the objective. Suppression of
the cough with anti-tussives should be avoided, as this
will result in a further accumulation of mucus within
the lower airways and exacerbation of the clinical signs.
Eosinophilic bronchopneumopathy
Eosinophilic bronchopneumopathy is also termed
pulmonary infiltrates with eosinophils (PIE) and
eosinophilic pneumonia. Eosinophilic lung disease
is not well understood, but certainly an eosinophilic
cell response can be seen with parasitic lung disease
(see later); but in the absence of that, the condition
is termed idiopathic. The severity of this condition
ranges from very mild, with minimal evidence on radi-
ography or bronchoscopy, to severe airway changes
that can mimic chronic bronchitis. However, airway
cytology (from a BAL) demonstrates a predominately
Fig 6: A cropped radiograph of a dog with a marked
bronchial pattern in the lung fields, in this case
associated with chronic bronchitis
Figure 7: Endoscopic view of a dog with chronic
bronchitis, showing the irregular mucosal lining,
presence of excess mucus and the associated
narrowing of the bronchial lumen
Fig 4: Dorsoventral
view of a young
labrador showing the
presence of a soft
tissue opacification
of the right caudal
lobe bronchus
associated with
inhalation of a large
wheat awn foreign
body (arrowed)
Fig 5: Endoscopic view of wheat awn foreign body
lodged in the bronchus of a young labrador
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eosinophilic cell response. The predominant clinical
sign in the vast majority of cases is a cough; however,
severely affected dogs can also present with dyspnoea
and exercise intolerance. Abnormal lung auscultatory
findings are heard in some severe cases (eg, crackles,
wheezes). Thoracic radiographs may show a general-
ised broncho-interstitial pattern and sometimes also
patchy or focal alveolar patterns. Occasionally, some
dogs present with an eosinophilic granuloma, which
can mimic a neoplastic mass (or nodular metastases).
The diagnosis is reached with bronchoscopy and air-
way cytology. Before embarking on medication with
steroids, it is essential to rule out parasitic disease,
which is a relatively common cause of an eosinophil-
ic airway disease in the British Isles, by appropriate
anthelmintic medication. The treatment of idiopathic
eosinophilic bronchopneumopathy involves the com-
bination of steroids and bronchodilators for several
months, aiming to reduce the dose of steroids to the
lowest effective dose with a 48 hour dosing interval.
Lungworm disease
Lungworm disease primarily causes a cough in dogs
and is associated with a number of lungworms in the
British Isles: Angiostrongylus vasorum, Crenosoma
vulpis and Oslerus osleri. It is more commonly found
in young dogs, but can be seen in middle aged dogs
too. In more severe infections associated with A vaso-
rum and C vulpis, dyspnoea can be an additional
clinical sign to coughing. In these cases, radiographs
usually show a mixed interstitial-bronchial pattern in
the caudodorsal lung fields, often with focal patches
of an alveolar pattern (which is associated with haem-
orrhage in the lung tissue). A vasorum can also cause
other clinical signs such as neurological and haemor-
rhagic diathesis. A diagnosis can be made by finding
larvae in faeces (Baermann technique) or in BAL fluid
(Fig 8). However, a negative finding does not rule out
the presence of lungworm infection. Real-time poly-
merase chain reaction (PCR) assay is now commer-
cially available for A vasorum (but not C vulpis or O
osleri). This PCR assay can be run on BAL fluid and
faeces, as well as blood, lung tissue and endotracheal
mucus. In suspicious cases, anthelmintic medication
should be administered and the response assessed.
Idiopathic pulmonary fibrosis
Idiopathic pulmonary fibrosis (IPF) seems to
affect mainly terrier type breeds, particularly West
Highland white terriers and cairn terriers. A gradual
decrease in exercise tolerance is the main complaint,
with some dogs also presenting with a chronic cough.
The most characteristic finding is marked pulmonary
crackles on auscultation, particularly in the ventral
lung fields, which may be associated with an expira-
tory wheeze. Chest radiographs typically show a dif-
fuse and widespread interstitial pattern in the lungs,
although there is sometimes a degree of bronchial
markings too (Fig 9). There is often some degree of
right-sided cardiomegaly as well. Pulmonary hyper-
tension can develop in chronic cases, leading to
echocardiographic findings of right ventricular
hypertrophy and pulmonary artery dilation (cor
pulmonale). CT is considered one of the most use-
ful diagnostic tests with characteristic pulmonary
changes. Palliative treatment can be offered for the
pulmonary hypertension and secondary inflamma-
tory complications (steroids and bronchodilators),
but there is no specific treatment available for this
disease.
Aspiration pneumonia
Aspiration pneumonia is primarily a chemical/par-
ticulate pneumonitis, which may or may not develop
secondary infection. It can be secondary to condi-
tions such as swallowing disorders, megaoesophagus,
BOAS and laryngeal paralysis. Clinical signs often
associated with aspiration pneumonia can include
tachypnoea and a cough that is often soft in nature.
It is important to perform a full neurological exami-
nation before other diagnostic procedures, particu-
larly involving general anaesthesia. The characteristic
radiographic appearance is an intense or consolidated
to variable alveolar pattern in the ventral lung lobes
(Fig 10), where aspirated food/saliva/material trickles
down to the tracheal carina and then falls by grav-
ity into the ventral lung lobes (Fig 11). Bronchoscopy
usually demonstrates a purulent airway discharge and
BAL can be submitted for cytology and bacteriology.
A barium swallowing study under fluoroscopy is nec-
essary to diagnose underlying swallowing disorders.
Fig 8: Endoscopic view of the distal trachea in a dog
showing the presence of a lungworm. During the
endoscopy, the worm can be seen wriggling (which
helps to dif ferentiate it from a strand of mucus)
Fig 9: A right lateral chest radiograph from a West
Highland white terrier with idiopathic pulmonary
fibrosis. There is a diffuse and widespread interstitial
lung pattern and a right-sided cardiomegaly
(suggestive of cor pulmonale)
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The treatment relies primarily on antibiotics, but
additionally bronchodilators, nebulisation and cou-
page can help.
Pulmonary haemorrhage
Pulmonary haemorrhage, when caused by anti-coag-
ulant poisoning, results in both severe dyspnoea and
coughing. While this is an uncommon presentation of
vitaminK antagonist rodenticide poisoning (eg, war-
farin), it is seen occasionally. However, if there is not
haemoptysis, then the diagnosis can be challenging.
Chest radiographs will show a widespread alveolar
pattern often throughout the lung fields (although
there may be a mild gravitating distributing to the
ventral lung lobes) that can mimic pulmonary oede-
ma. Diagnosis is usually confirmed on blood work
(coagulation profile) when this is a differential.
Pulmonary neoplasia
Pulmonary neoplasia can be primary or metastatic
and usually affect middle-aged to older dogs. The
clinical presentation can range from asymptomatic or
mild to severe coughing, sometimes with haemoptysis
or systemic signs. In general, it is only large or wide-
spread neoplastic disease that triggers coughing; small
peripheral nodules generally do not reach the location
of the cough receptors. Thoracic radiographs vary
considerably depending upon the nature and origin of
the neoplasia. Metastatic disease can vary from an ill-
defined nodular pattern (Fig 12) to large ‘snowball’
type lesions. Large solitary masses (Fig 13) involving
one or even more lung lobes are seen and sometimes
a fine diffuse interstitial pattern associated with car-
cinomas is possible. The diagnosis is usually achieved
with a combination of thoracic radiographs, endosco-
py and cytologic sampling where possible. Endoscopy
may demonstrate the extraluminal compression of an
airway and the associated inflammatory response (Fig
14). Undoubtedly, CT allows for a better identification
and assessment of neoplastic lung lesions.
Cardiac disease
Left-sided heart enlargement
Compression of the left mainstem bronchus is the most
common cause of coughing associated with left-sided
cardiomegaly and heart disease in dogs (Fig 15). This
is most commonly associated with mitral valve disease
and dilated cardiomyopathy, which produce left atrial
dilation (as well as left ventricular dilation) and thus
extra-luminal compression of the mainstem bronchus.
However, there is some debate about whether dogs that
cough with heart disease may in fact have concurrent
bronchomalacia, contributing to the airway compres-
sion and inflammation. It is rare for right-sided heart
enlargement to cause coughing.
Fig 10: A right lateral chest radiograph of a dog
showing consolidation of the ventral lung lobes
(arrowed), which is a location most suspicious of
aspiration pneumonia in dogs
Fig 11: A right lateral chest radiograph of a dog with
a large dilated air filled megaoesophagus, with
accumulation of food within the cranial portion with
ventral deviation of the oesophagus (red arrows).
There is also consolidation of the cranial lung lobe
indicative of aspiration pneumonia (black arrows)
Fig 12: A right lateral chest radiograph from a dog
with a widespread nodular or miliary lung pattern
consistent with metastatic neoplasia
Fig 13: A right lateral chest radiograph in a dog with
a large mass lesion in the hilar region. A dorsoventral
radiograph would be required to determine the
location of this to establish if it is mediastinal (such
as a hilar lymph node enlargement) or in a lung lobe
(such as a primary lung tumour)
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516 In Practice October 2013 | Volume 35 | 503-517
Pulmonary oedema
Dyspnoea and tachypnoea are the main features
of pulmonary oedema; however, when the oedema
fluid spills into the airways, it can trigger the cough
receptors.
Pericardial effusion
Coughing is also associated with acute onset pericar-
dial effusion. While it is assumed this is associated
with compression of airways, similar to left atrial
Fig 14: Endoscopic view
of a bronchus in a dog
in which the bronchus is
seen to be compressed
by an extra-luminal mass,
resulting in closure of the
airway as well as mucosal
inflammation
Fig 15: A right lateral
chest radiograph of a
cavalier king charles
spaniel with mitral
valve disease. There is
massive left atrial dilation
resulting in compression
of the mainstem bronchus
(arrowed), a common
trigger for coughing in
dogs with heart disease
Fig 16: A dorsoventral
radiograph of the chest
of a whippet in which
there is a large volume
of pleural effusion with
retraction and leafing of
the lung lobes from the
chest wall. In addition,
the cranial lung lobes
are displaced caudally
(arrowed) to such a
degree that it is suspicious
of the presence of a
cranial thoracic mass. This
can only be confirmed by
ultrasound examination
dilation, this is not always the case. Some dogs can
present with coughing, yet only a small volume of
pericardial effusion is present. The mechanism is not
understood, but may well be inflammatory related.
Pleural space disease
Compression of airways, and thus coughing, can
occur when there is a large mass within the chest,
such as a cranial mediastinal mass. Thoracic radiog-
raphy will typically demonstrate a large mass (or the
presence of pleural effusion) that is causing abnormal
displacement of the lung lobes, airways or heart (Fig
16). If radiographs demonstrate what appears to be
only a pleural effusion then a thoracocentesis should
be performed, the fluid drained, measured, classified
and analysed, following which repeat radiographs
should be performed. Additionally, ultrasound of the
chest is particularly useful in identifying the presence
of a thoracic mass as well as facilitating fine needle
aspirate (FNA) or Trucut biopsy of any mass present
(Fig 17).
Oesophageal conditions
Megaoesophagus or oesophageal disorders can result
in accumulation of food and saliva within it, which
typically triggers regurgitation, but can sometimes
Fig 17: An ultrasound image of a cranial thoracic mass
showing a Trucut biopsy being positioned within the
mass. This can be seen entering from the left side of
the image at the level of the 2 cm mark (arrowed)
Figure 18: A right lateral chest radiograph from a young
German shepherd dog after being fed food containing
barium. This shows a dilated oesophagus in which there
are rugal folds in the distal oesophagus indicative of
a gastro-oesophageal intussusception. This is often
best appreciated during a conscious fluoroscopic
examination to observe the movement of the stomach.
There is also aspiration of barium into the trachea
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517
In Practice October 2013 | Volume 35 | 503-517
produce retching or be confused with a retching type
cough on taking the history. The regurgitation or
retching of copious volumes of food and liquid can
result in accidental inhalation, leading to aspiration
pneumonia. Many cases of megaoesophagus are idi-
opathic, but acquired causes include focal myasthe-
nia gravis and hypothyroidism. Aspiration may result
from neuropathy/myopathy affecting the guarding of
the larynx during deglutition and some of these dogs
do not have normal laryngeal function. Congenital
causes are uncommon, but a persistent right aortic
ring would be the most familiar and the clinical signs
become apparent when the pup is weaned onto solid
food. A hiatal hernia (seen in bulldogs with BOAS) or a
gastro-oesophageal intussusception can result in retch
and regurgitation and the complication of aspiration
pneumonia (Fig 18). Diagnosis is often based on the
history, but with a degree of luck may be seen on a
barium study under fluoroscopic imaging.
Summary
There are a wide variety of conditions that can cause
coughing in dogs. The history and the physical exami-
nation can help differentiate coughing associated
with upper airway disease or cardiothoracic disease.
Typically, a cough arising from the larger upper air-
ways is often loud, in contrast to that of smaller (lower)
airways, which is often soft. Additionally, an under-
standing of the location of the cough receptors is key
to unders tanding how best to invest igate coughi ng. For
conditions within the chest then x-rays and proBNP
are often useful. If respirator y disease is suspected, the
diagnostic protocol usually comprises airway inspec-
tion under general anaesthesia and bronchoscopy with
airway cytology (bronchoalveolar lavage) is usually
required for final diagnosis. Thoracic masses require
ultrasound examination and biopsy. Once the diagno-
sis is reached, an appropriate therapeutic protocol and
a realistic prognosis can be formulated.
Reference
MARTIN, M. & MAHONEY P. (2013) Improving the
diagnostic quality of thoracic radiographs of dogs and cats. In
Practice 35, 355-372
Further reading
BONAGURA , J. D. & TWEDT, D. C. (2009) Kirk’s Current
Veterinary Therapy XIV. Saunders
ETTINGER, S. J. & FELDMAN, E. C. (2010) Textbook of
Veterinary Internal Medicine. 7th edtn. Elsevier Saunders
FUENTES, V. L., JOHNSON, L. R. & DEN NIS, S. (2010)
BSAVA Manual of Canine and Feline Ca rdiorespiratory
Medicine. BSAVA
JOHNSON, L. R. (2010) Clinical Canine and Feline Respiratory
Medicine. Wiley-Blackwell
KING, A. S. (1999) The Cardiorespiratory System: Integration
of Normal and Pathological Structure and Func tion. Blackwell
Science
KING, L. G. (2004) Textbook of Respiratory Disease in Dogs
and Cats. Saunders
MARTIN, M. & CORCORA N, B. (2006) Notes on
Cardiorespiratory Diseases of the Dog and Cat. Blackwell
Publishing
For more information visit
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Approach to the coughing dog
Mike Martin and Yolanda Martinez Pereira
doi: 10.1136/inp.f5838
2013 35: 503-517 In Practice
http://inpractice.bmj.com/content/35/9/503
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  • Kirk's Current Veterinary Therapy XiV
    • J D Bonagura
    • D C Twedt
    BonAguRA, J. D. & TWEDT, D. C. (2009) Kirk's Current Veterinary Therapy XiV. Saunders.
  • Textbook of Veterinary internal Medicine
    • S J Ettinger
    • E C Feldman
    • V L Fuentes
    • L R Johnson
    • S Dennis
    ETTingER, S. J. & FELDMAn, E. C. (2010) Textbook of Veterinary internal Medicine. 7th edt. Elsevier Saunders. FuEnTES, V. L., JohnSon, L. R. & DEnniS, S. (2010) BSAVA Manual of Canine and Feline Cardiorespiratory Medicine. BSAVA.
  • The Cardiorespiratory system: integration of normal and Pathological Structure and Function
    • A S King
    King, A. S. (1999) The Cardiorespiratory system: integration of normal and Pathological Structure and Function. Blackwell Science.
  • Textbook of respiratory disease in dogs and cats
    • L G King
    King, L. g. (2004) Textbook of respiratory disease in dogs and cats. Saunders.
  • Textbook of Veterinary Internal Medicine
    • J D Twedt
    • D C Saunders
    • S J Feldman
    • L R Dennis
    BONAGURA, J. D. & TWEDT, D. C. (2009) Kirk's Current Veterinary Therapy XIV. Saunders ETTINGER, S. J. & FELDMAN, E. C. (2010) Textbook of Veterinary Internal Medicine. 7th edtn. Elsevier Saunders FUENTES, V. L., JOHNSON, L. R. & DENNIS, S. (2010) BSAVA Manual of Canine and Feline Cardiorespiratory Medicine. BSAVA
  • Book
    Notes on Cardiorespiratory Diseases of the Dog and Cat is part of a series specifically designed, through an accessible note–based style, to ensure veterinarians and students have quick and easy access to the most up–to–date clinical and diagnostic information. Since the first edition, there have been many developments in this field, particularly in the area of cardiology. This new edition has been completely revised and updated, and now includes the latest information on the diagnosis and treatment of cardiorespiratory diseases. Full of helpful tips and ideas, the authors offer their expert advice on the more common diseases, with some references to rarer conditions. This edition includes: Completely revised new edition, now in the Notes On series, detailing the latest developments in the treatment of heart disease; Practitioner orientated, with full guidance on how to achieve the best diagnostic results for radiography, echocardiography and airway samples; Includes a drug glossary, table for CPR and useful appendices on breed predispositions and normal echo–values for dogs and cats; Written by experienced clinical experts in cardiorespiratory medicine.
  • Article
    Full-text available
    Evaluating a series of thoracic radiographs may be one of the most challenging imaging tasks confronting the small animal clinicians in their daily practice. Pathological changes can sometimes be quite subtle, while at other times they can be confusing in their complexity. Radiographs that are not of optimal quality only add to this confusion, either by hiding pathological changes or creating artifacts that resemble pathology. In the ideal world, every thoracic radiograph would be perfect and the clinician's task would be easier. In the real world, patients with intrathoracic disease can be high risk and difficult to position, and a balance needs to be struck between patient safety and diagnostic quality. This article describes how to get the most out of thoracic radiographs by improving the diagnostic quality of radiographic films.