By Jean Duddy, DVM
The first challenge when treating a coughing cat is determining if the cat is actually coughing. Gagging (such as with a hairball) or choking will need to be ruled out. Since owners often cannot tell the difference in this day of cell phone videos: it is very helpful to have your owner video this at home. It is not very common we have a cat come into our exam room and cough for us.
A cough is a defensive mechanism or reflex of the respiratory system. It is used to dispatch foreign material from the airways. A cough occurs due to stimulation of mechanoreceptors or chemoreceptors within the respiratory tract itself. These cough receptors are located throughout the entire respiratory tract from the pharynx to the bronchioles. So a cough is very nonspecific and does not tell us if it is upper or lower airway issues.
Once we have determined there is coughing going on we need to get a good history as this will help guide us for our determination of the etiology of the cough. Is the cough acute or chronic? Any cough for more than 2 weeks is considered chronic. A young cat with acute coughing and nasal discharge is more likely to have an infectious or foreign body reaction while an older cat with worsening coughing and weight loss may be more likely to have neoplasia or asthma.
Timing of the cough may give us some hint as well. Coughing after eating/drinking may indicate laryngeal dysfunction. Knowing if this is the first episode (or occurs only seasonally) as well as response to any previous therapy will also help focus the search for the etiology of the cough.
Cats that are in respiratory distress should be provided with oxygen immediately while stable cats should be observed prior to the actual physical exam. The exam is an important part of localization of the cough even though it is rare you will actually observe a cough. Observation of the cat’s respiratory rate and pattern as well as any respiratory noises may give insight to the source of the cough. Stertorous respiration or inspiratory dyspnea may indicate laryngeal or upper airway disease. While wheezing may indicate lower airway disease.
Be methodical in your physical exam. A “look, listen and feel” approach is often best. Look from a distance to see the breathing patterns. Listen for breathing noises both with and without a stethoscope then feel or conduct your physical exam.
- Check oral mucus membranes for color (cyanosis, pale). Check for any abnormalities in the mouth foreign material, masses, ulcerations, trauma, etc.
- Check the nasal passages for airflow, discharge or masses. Are there any malformations?
- Palpate over the trachea and larynx to detect masses or sensitivity. Can a cough be induced?
- Palpate the rib cage for masses and gauge the ability to compress the chest (excessive resistance can indicate fluid or mediastinal mass).
- Now conduct auscultation over all parts of the respiratory tract over the larynx, trachea and the lung fields.
- Inspiratory noises are usually from the upper respiratory tract (nose, pharynx, larynx or trachea).
- Expiratory noises are usually from the lower respiratory tract (lower airways and pulmonary parenchyma). Wheezing may mean airway narrowing while crackles or moist sounds may indicate fluid within the lumen of the airway.
- Remember with some diseases such as feline asthma, cats may auscult totally normal.
- Palpation of the larynx and trachea can be done to check for masses or try elicit a cough in the exam room.
- Complete your entire physical exam – things such as abdominal masses can impinge on the diaphragm and cause increased respiratory rates and increased effort. Unlike dogs, cats do not cough that often from congestive heart failure but heart murmurs and arrhythmias should be noted for further evaluation.
Once we have determined the cat is coughing, the next step is to localize it to one area of the respiratory tract. Then a list of differential diagnoses will help determine the next round of diagnostic tests to be done. A minimum data base is indicated for all of these cats including a CBC and biochemical profile. Other testing may include retrovirus testing for FeLV and FIV, PCR testing for respiratory viruses (feline herpesvirus FHV-1 and feline calicivirus (FCV)).
Oropharyngeal disease may be characterized by a gurgle or rattling cough often followed by retching. Other respiratory signs such as stertor or inspiratory dyspnea are also often observed. There also can be excessive salivation or nasal and/or ocular discharge present.
Common causes of oropharyngeal diseases would be pharyngitis (infectious or foreign body), nasopharyngeal polyp, neoplasia or even trauma.
Diagnostics would include a sedated (or anesthetized) oral exam. To evaluate for a nasopharyngeal polyp, use a spay hook to retract the soft palate and a dental mirror to see if there is a mass/polyp. Lateral skull radiographs or CT should be obtained to check the tympanic bullae for an increased soft tissue density which may be associated with the polyp.
Upper Airway (Larynx/Trachea) disease is characterized by a dry harsh cough and stridor. Noisy breathing pattern may present on inspiration.
Common causes would include laryngitis, tracheitis (infectious, foreign body, neoplasia) or laryngeal paralysis.
Diagnostics would include radiographs to evaluate the trachea for narrowing or any mass lesions. A sedated (or anesthetized) airway exam to evaluate laryngeal structures and function (movement of the larynx). Endoscopic evaluation may be needed to fully assess the trachea.
Caution should be taken here to control the airway especially if dealing with laryngeal or tracheal masses. Even minimal handling of these masses (such as a biopsy) can cause enough inflammation that emergency measures such as a tracheostomy may be needed. These cats should be closely monitored while they are waking up for any airway obstructions.
Lower Airway (Bronchial tree) disease is characterized by a dry, harsh cough with wheezing and possibly crackles on auscultation. There is more of an abdominal effort by the cat when breathing.
Common causes would be asthma and chronic bronchitis (+/- concurrent infections), foreign body or neoplasia.
Diagnostics would include thoracic radiographs, fecal flotation and Baermann technique to rule out Aelurostrongylus abstrusus and Eucoleus aerophilus (feline lung worm). Bronchoscopy and bronchoalveolar lavage (BAL) should be performed to obtain samples for cytology, bacterial cultures and PCR testing for Mycoplasma spp. and Bordetella bronchiseptica.
Pulmonary parenchyma diseases often have a moist cough and crackles on auscultation.
Common causes would be bronchopneumonia (infectious, or secondary to aspiration), neoplasia, edema (cardiogenic or noncardiogenic), heartworm disease, hemorrhage or pulmonary fibrosis.
Diagnostics would include radiographs, echocardiogram/EKG +/- BP and T4 if a murmur or arrhythmia is detected, and a coagulation panel if a hemorrhage is suspected. Toxoplasmosis IgM and IgG titers should be considered if appropriate. Otherwise a BAL should be performed to obtain samples for cytology, cultures and PCR testing.
Pleural space diseases do not often cause coughing but do cause respiratory compromise and distress. Dull heart sounds and loss of airway sounds on auscultation may be noted. Also the chest may be less compressible on palpation. Neoplasia (mediastinal masses such as lymphoma or thymoma) or pleural effusion from cardiac disease or neoplasia are some of the common diseases. Diagnostics would inclulde radiographs or if those are too stressful, a thoracic ultrasound will help confirm fluid or a mediastinal mass. An echocardiogram and thoracocentesis for pleural effusion sampling would then be indicated.
In summary, a good history is important as most cats do not show symptoms of minor respiratory disease in the exam room. Be methodical in your physical exam especially when dealing with the respiratory tract. Localize the cough to a specific area of the respiratory tract so a list of differential diagnoses can be made and appropriate diagnostics can be done. This will help you come up with a definitive diagnosis and begin specific treatment.
For more information, contact Angell’s Internal Medicine service at 617-541-5186 or firstname.lastname@example.org.