Cough is a clinical symptom, but not a disease complex in its own right. The cause should be clarified in the differential diagnosis.
The cough reflex can be triggered by foreign material or secretions in the airways, inflammation, or pressure exerted on the airways; However, coughing can also be voluntary. Coughing is a natural protective and cleaning mechanism for the respiratory tract.
Since cough therapy should be aimed at the underlying disease as far as possible, a diagnostic workup is usually useful, especially in the case of a chronic problem.
Differential diagnoses and diagnostic procedures
The most common causes of cough are diseases of the respiratory tract, here a distinction can be made between the upper and lower respiratory tract. In addition, heart disease can be accompanied by coughing and diseases of the pleural cavity, especially in dogs. When investigating the cause, factors such as the age and race of the patient, history, and clinical examination can provide important assistance before further diagnostics are initiated. X-rays, endoscopy, CT, histological, cytological, and microbiological examinations can also help with the diagnosis.
Young animals are particularly frequently presented with respiratory infections (cat cold, canine infectious tracheobronchitis, Bordetella infection, distemper), while heart and tumor diseases are more common in older patients.
Certain breeds are predisposed to some diseases, such as heart disease in breeds like the Persian, Boxer, Doberman Pinscher, and many others, or tracheal collapse in miniature breeds like Yorkshire Terriers, Pomeranians, and Chihuahuas.
Here it is particularly important after the previous vaccination report (cat cold, distemper, tracheobronchitis pathogens), previous report abroad (heartworms), free range in cats (lungworms, trauma), and of course the symptoms (type, duration, previous treatments and possible response to previous therapies, nasal discharge, sneezing, poor performance, Shortness of breath, known pre-existing/concomitant illnesses and previous diagnostics). Existing findings (laboratory, X-ray, cardiac ultrasound) should be brought by the owner to the appointment if possible.
The clinical examination should include, in addition to a general examination of the patient, a special thorough examination of the respiratory tract. In addition to assessing the type of breathing and possible signs of shortness of breath, it is also important to pay attention to any nasal discharge. When auscultating the patient, the upper airways (larynx/pharynx area) as well as the lungs and heart should be listened to check for signs of possible constrictions (whistling noises), increased breathing noises via the bronchi and lungs or heart noises/arrhythmias (possible indication of a heart problem ) are present. In many cases, slight pressure in the area of the larynx or trachea can trigger a cough.
Dogs and, more rarely, cats with infectious, especially viral and bacterial respiratory diseases, can clinically show an elevated body temperature, but a normal temperature or hypothermia does not rule out an underlying infection.
Patients with chest effusion usually show shortness of breath as the main symptom. Depending on the amount of effusion, muffled heart sounds and breathing sounds can be determined on auscultation.
Common causes, diagnostics, and therapy
Upper respiratory tract
In the upper respiratory tract, coughing can be caused by the inflammatory, infectious, tumorous, or functional changes in the area of the nasopharynx, larynx,x, and the upper part of the trachea. These patients often show a clear upper breathing sound due to constriction. Coughing can often be triggered by slight pressure on the larynx or trachea.
Acute cough symptoms can be triggered by a foreign body or an acute infection (cat flu complex, canine infectious tracheobronchitis = kennel cough). In the case of chronic problems, especially in miniature dog breeds (Yorkshire Terrier, Spitz, Chihuahua), a tracheal collapse should be considered. Rhinitis can also trigger coughing due to secretions running backward. The diagnostic clarification of a cough localized in the upper respiratory tract includes X-ray examinations of the throat and larynx to obtain evidence of narrowing, soft tissue dense growths, or collapse of the air ducts. Further clarification, especially of a chronic cough, is carried out by using endoscopy of the nasopharynx, larynx a, and trachea, with Biopsy samples or cytological smears of changes can be taken. The function of the larynx is assessed before possible intubation into the brain indicating restricted function (larynx paralysis). Tracheoscopy is the diagnosis of choice for detecting and assessing (degree and extent) a tracheal collapse (see Figure 1 in the picture gallery).
Lower respiratory tract
Diseases in the bronchi, alveoli, and lung tissue are common causes of coughing. In general, it can often be observed that diseases of the large airways (e.g. tracheal collapse, bronchitis, bronchial collapse) lead to a loud, dry cough, while diseases of the alveoli and Lung parenchyma (e.g. pneumonia, pulmonary edema) are more likely to be accompanied by a soft, wet cough. A stridor noise in the area of the bronchial tubes often occurs in cats with chronic bronchial diseases (feline asthma, bronchitis).
Occasionally there are foreign bodies in the lower respiratory tract or chronic infections (mostly bacterial: e.g. Bordetella infection). Lung tumors occur less frequently.
While patients with tracheal collapse typically belong to toy dog breeds, the collapse of one or more sites in the bronchial tree is also common in larger dog breeds. Around 80% of dogs with a tracheal collapse also have a bronchial collapse, which can significantly aggravate the coughing symptoms. A collapse of the trachea or individual bronchial sections can best be detected endoscopically.
Chronic bronchitis occurs mostly in middle-aged and older dogs. The disease is characterized by chronic inflammation of the bronchi, which also leads to excessive mucus production. The dogs show coughing and often poor performance. The cause is not yet known.
Infectious causes of cough in dogs and cats can be viruses (cats: herpes and caliciviruses; dogs: kennel cough complex, distemper), bacteria ( bordetella bronchiseptica, Streptococcus zooepidemicus or other bacterial pathogens), parasites (dogs: Angiostrongylus vasorum, Filaroides osleri, Crenosoma vulpis, cat: Aelurostrongylus abstrusus ) and only very rarely infections with fungi or protozoa ( Toxoplasma gondii, Neospora caninum) be. While viral infections of the respiratory tract typically trigger acute cough symptoms, bacterial and parasitic infections can also be associated with a chronic cough.
Further diagnostics in respiratory diseases
In some cases, the laboratory can also provide information about the type of underlying disease. In patients with bacterial bronchopneumonia, neutrophilic granulocytes and rod-nuclear neutrophils (left shift) may be increased. Dogs with bronchopneumonia may have significantly elevated levels of C-reactive protein (CPR). In cats with feline asthma, there may be an increase in eosinophilic granulocytes in the blood count, as well as in patients with lung parasites.
In dogs and free-roaming cats, lungworm infection must be ruled out if there are chronic respiratory symptoms and coughing. This can be done by detecting excreted lungworm larvae using the Baermann emigration method in fecal samples or by cytological detection of the larvae in the BAL fluid (see Figure 2 in the picture gallery). If possible, three different stool samples should be examined. Detection of the dog lungworm Angiostrongylus vasorum can now also be carried out using pathogen detection (PCR) from BAL fluid or blood. There is also a rapid test for detection from serum.
X-rays of the heart/lungs and, if necessary, the trachea help to localize and better classify a respiratory problem. If the patient’s condition permits, they should be made in three planes, or at least in two planes (anterolateral and ventrodorsal or dorsoventral). In this way, indications of possible underlying diseases can already be obtained (e.g. suspected bronchial disease with bronchial lung markings, suspected pneumonia with alveolar lung markings; see Figure 3 in the picture gallery). There may also be indications of heart disease (enlarged heart shadow, congested pulmonary vessels) or thoracic effusion. If there is a suspicion of a problem in the airways (airway collapse, bronchitis, foreign bodies, bronchopneumonia), an endoscopic examination of the upper and lower respiratory tract is carried out under anesthesia. Of course, this examination should only be carried out on stable patients, who should be monitored during anesthesia with pulse oximetry and, if possible, also with ECG and capnography. A bronchoscopy with a flexible endoscope (special models available for larger dogs or cats and small dogs) also enables the targeted collection of bronchoalveolar secretions using bronchoalveolar lavage(BAL). BAL can also be performed “blindly” with a sterile probe through a sterile tube (see Figure 4 in the image gallery). A few milliliters of sterile saline solution are injected into the lower respiratory tract via a probe and then suctioned out again. The BAL fluid should then be examined cytologically and culturally to further clarify infectious and inflammatory underlying diseases.
Primary lung tumors in dogs and cats are rather rare causes of coughing, most tumors are metastases from other localizations. The most common primary lung tumors in dogs and cats are carcinomas (see figure 5 in the picture gallery). If there is radiographic evidence of a lung tumor, computed tomography can be used to more accurately assess a mass and look for metastases and lymph node involvement. Radiologically, tumor metastases can only be detected from a size of 3–5 mm.
A common question in dogs is the differentiation between cardiac and respiratory cough. It is often not easy to find the cause, since many old patients have a heart murmur and a chronic respiratory disease at the same time. Common cardiac causes that lead to coughing in dogs are diseases that lead to heart failure and subsequent pulmonary edema or pressure on the left main bronchus due to enlargement of the left heart. If pulmonary edema already exists, shortness of breath is usually the main clinical symptom in the patient.
To be able to make a clear diagnosis in a patient with suspected heart disease, however, further examinations such as X-rays, heart ultrasound, and ECG are required necessary. The ECG examination serves to more precisely classify arrhythmias. X-ray images allow an objective assessment of the size of the heart (according to the scheme of the VHS = Vertebral Heart Score), the pulmonary vessels, and possible lung patterns. A cardiac ultrasound allows for the precise determination of the chamber dimensions and assessment of the valve functions and can thus enable an exact diagnosis of underlying heart disease and possible volume overload of the heart. In addition, biomarkers such as the nt-proBNP can help differentiate between a cardiac and a respiratory cause for cough and dyspnea (shortness of breath).
Large space-occupying processes or effusion in the thorax can also trigger a cough. These can be tumors, granulomas, abscesses, enlarged lymph nodes, or diaphragmatic hernias. Clinically, patients with effusion usually show shortness of breath rather than coughing. Radiologically, an overview of the extent and distribution pattern of the changes can be obtained (unilateral or bilateral effusion, location, size of masses, etc.); Computed tomography enables an even more precise assessment of the changes compared to x-rays. Furthermore, an ultrasound can be a useful addition to the clarification. Larger increases in circumference can thus often be visualized and—if they are adjacent to the chest wall—can be punctured for a cytological examination. Smaller accumulations of effusion can also be excellently visualized using ultrasound. After puncture of the effusion, which should ideally be carried out under ultrasound control, a cytological, chemical and, if necessary, bacteriological examination of the liquid enables further differentiation.
Other less common problems that lead to coughing are diseases of the interstitial lung tissue such as pulmonary fibrosis (particularly in West Highland White Terriers). Pulmonary lobe torsion, pulmonary hemorrhage, and thromboembolism can also be associated with coughing and/or shortness of breath.
Therapy for a coughing patient depends on the root cause.
Viral infections of the respiratory tract (kennel cough) are self-limiting in dogs and usually do not require therapy if there is no fever and poor general health. If the animals show signs of a bacterial infection (fever, leukocytosis, reduced general condition, signs of pneumonia in the X-ray), the therapy should include a suitable antibiotic in addition to general supportive measures such as expectorants and inhalation. In chronic cases, in particular, the administration of antibiotics should be based on the results of culture and resistance tests from a BAL.
Lungworms should be treated with a suitable antiparasitic agent approved for the species. After completion of the therapy, a renewed 3-day collection of stool examination using an emigration procedure is recommended as proof of the success of the therapy and regular prophylaxis to prevent further infections.
In the case of infections of the respiratory tract, the cough reflex should be supported as an important self-cleansing process. Cough-suppressing medication should not be given, nor should any cortisone preparations have an immunosuppressive effect.
Therapy in dogs with collapsed airways usually consists of several components. In many cases, a strong urge to cough can be suppressed or reduced through the use of codeine preparations. In addition, bronchodilator drugs such as theophylline, propentophylline, terbutaline, or salbutamol inhalation) can bring improvement. In animals with severe tracheal collapse, a stent (supporting metal coil) can be placed in the trachea.
chronic bronchitis and feline asthma
The treatment of choice for chronic bronchitis (dogs and cats) and feline asthma is the administration of cortisone preparations. After the initial therapy, systemic cortisone therapy should be dosed as low as possible and, if possible, switched to a cortisone spray (e.g. fluticasone, budesonide) in the long term. Special inhalation chambers can be used to administer the spray. In addition, some animals may need bronchodilator medication to reduce symptoms.
Neoplasms of the larynx and trachea are rare in dogs and cats, while primary lung tumors are uncommon. Surgical removal of a lobe of the lung only makes sense if no other lobes or lymph nodes are affected and there is no thoracic effusion, so a CT scan should always be performed before the operation. Chemotherapy can also help with occasional lymphomas of the trachea or lungs, especially in cats.
Here, the specific therapy depends on the underlying cardiac disease. Diuretics (water tablets such as furosemide, and torasemide) are an important part of therapy for all patients who show signs of volume overload or pulmonary edema. Additional cardiac drugs (ACE inhibitors, pimobendan, antiarrhythmics) are used depending on the nature of the underlying disease. In some patients with a cough that persists during therapy and suspected compression of the bronchi due to an enlarged heart, therapy with codeine preparations may also be indicated to suppress the urge to cough.
In patients with chest effusion, this should be drained for both diagnostic and therapeutic purposes. The further therapeutic steps then depend on the respective cause of the effusion.
Heart failure or respiratory?
On clinical examination, dogs with heart failure often present with an increased heart rate, while dogs with a respiratory cough often present with a normal or even slow heart rate due to increased vagus nerve tone. In addition, dogs with respiratory diseases often show a pronounced sinus arrhythmia (respiration-related arrhythmia).
Chronic cough in cats
In cats, a chronic cough usually indicates a bronchial disease, in many cases, there are underlying inflammatory diseases such as feline asthma and chronic bronchitis. These are sterile inflammations without pathogen involvement; increased eosinophilic or neutrophilic granulocytes can be detected in the lower airways. Bacterial or parasitic bronchitis can only be differentiated by examining flushing samples (bronchoalveolar lavage) from the lower airways.
Also, consider other factors!
In most animals with chronic respiratory problems, the improvement of concomitant factors plays a major role. The reduction of obesity as well as the therapy of other additional diseases (heart diseases, Cushing’s disease, thyroid diseases) and the changeover to a harness instead of a collar in dogs shows in many cases a great influence on the improvement of the respiratory symptoms.
Frequently Asked Question
What does a heart cough in dogs sound like?
Does he cough mainly in the evening when he is resting? – a very characteristic but often overlooked sign is cardiac cough. The dog shows repeated, quite loud coughing that is accompanied by a kind of gagging as if he wants to spit something out.
What does when the dog coughs and chokes mean?
If the dog is frequently coughing and retching, it should be examined by a veterinarian. The oral cavity, airways, and esophagus must be examined to identify foreign bodies, inflammation, or infection. The vet determines the affected organ system and initiates further diagnostics.
How do I recognize cardiac cough in dogs?
On clinical examination, a heart murmur is often audible and an increased heart rate is noted. Cardiac arrhythmias can also occur. Additional symptoms such as shortness of breath, rapid fatigue, heavy panting, poor performance, reluctance to exercise, or frequent restlessness are typical.
Is cardiac cough fatal in dogs?
However, most heart diseases do not mean a death sentence for the affected dogs, just a slightly different rhythm of life and permanent medication. Reluctance to exercise, panting even after minimal exertion, or coughing for no reason can be signs of heart disease in dogs.
What does it sound like when a cat coughs?
The cough has admixtures of other fluids (e.g. pus, mucus, blood, etc.) and causes acute or chronic pain. Shortness of breath, sneezing, choking, difficulty swallowing, nasal discharge, or breathing noises (e.g. rattling, whistling, etc.) often occur parallel to coughing.
How do you recognize lungworms in cats?
The signs of lungworm infestation can be non-specific: coughing, sneezing, eye, and nasal discharge, and shortness of breath are easily mistaken for the symptoms of other respiratory diseases such as cat flu or asthma.
Is coughing dangerous in cats?
When a cat coughs, there can be a variety of reasons. In most cases, the four-legged friend’s cough is completely harmless and quickly disappears. However, it is also quite possible that this is a symptom of a serious illness.
Is cat cough deadly?
For the cat owner, it can be very worrying. After all, there can be many reasons for this and not all of them are harmless. If the cough occurs not just once, but repeatedly, you should always consult a veterinarian.