Veterinary Cardiorespiratory Centre
Martin Referral Services, Thera House, 43 Waverley Road, Kenilworth, Warwickshire CV8 1JL
Tel: 01926 863445
INFORMATION SHEET
Guidelines on diagnostic investigation of respiratory disease
The diagnosis of respiratory signs such as coughing and dyspnoea can be challenging, particularly
in subtle or difficult cases. This information sheet aims to provide some aide memoirs on the diagnostic
procedures used in the diagnosis of respiratory disease. Alternatively, if it suits the owner, consider
referral..?
 Routine haematology submitted to the lab, together with fresh air dried smears, to ensure an accurate
assessment of the white cell differential and cell morphology.
 Rule out lungworm infection, particularly in coughing dogs, as this may avoid the need to embark on the
further investigations listed below. Treat with Panacur, use the ‘lungworm dose’ (50mg/kg fenbendazole)
daily for 7 to 14 days. Crenosoma vulpis (the fox lungworm) is commonly seen in central England,
Angiostrongylus vasorum is seen in Cornwall, South Wales and Kent, Aleurostrongylus abstrusus (cat
lungworm) is uncommonly recognised, but might act as an allergen for asthma and should therefore be
excluded from the differential diagnosis.
 Submission of a faeces sample for a larvae ‘search’ can be of value, but a negative finding is does not
rule out infection.
 Check for a history of a fox frequenting the dog’s garden.
Investigations performed under anaesthesia
 For laryngeal paralysis: check arytenoids are actively abducting on inspiration. The use if i/v dopram is
useful to increase respiratory effort during assessment, at a dose of 0.5 to1.0mg/kg. False positive and
false negative diagnoses are a potential pitfall. Examination for laryngeal paralysis should be performed
under very light GA, such that the gag reflex is presence and jaw tone is strong. Secondary features are
inflammation and/or erosion of the mucosal surface of the arytenoids and sometimes the presence of
saliva in the pharynx or even within the trachea.
 Examine the soft palate, pharynx and larynx closely for abnormalities.
Radiography
 Chest x-rays (in dogs) - right lateral and VD (or DV), preferably taken under GA, so that the lungs can be
inflated during exposure. This helps to ensure good aeration of the lungs (improves air to soft tissue
contrast) and reduces movement artifact. Under-aeration of lungs and movement blur makes assessment
of lung detail difficult and can lead to false positive diagnoses.
 To screen for tracheal collapse with plain radiography (diagnostic rate is ~50%), requires two lateral
films, collimated to show the whole of the trachea from larynx to carina, with one taken during
inspiration and one taken during expiration. However bronchoscopy is the diagnostic procedure of choice
(fluoroscopy is often useful).
 In cats - a common radiographic feature looked for is hyperinflation of the lungs due to air trapping as a
consequence of bronchoconstriction such as in asthma, thus do not inflate cat’s lung.
 If screening for metastases remember that obtaining right and left lateral views increases the chances of a
positive finding.
Endoscopy
 Bronchoscopy, with a broncho-alveolar lavage fluid sample (see also Information Sheet 9) submitted to a
cytologist to assess airway cell response (making air-dried smears of ‘spun’ sediment within 30 minutes).
Accurate assessment of the primary airway cell response is the key to diagnosing many lower airway
diseases, but there are pitfalls in obtaining good samples and upper airway contamination can cause
confusion.
 Bacteriology results are usually only significant when a significant number of bacteria are found on
cytology. False positive results are not uncommon due to culture of normal flora or contamination from
upper airways, the mouth or equipment.
Martin & Corcoran (2006) Notes on: Cardiorespiratory disease of the dog and cat, 2nd ed
Blackwell Science. ISBN 0-632-03298-7