There are no clinical studies of aspiration pneumonia (AP) in the dog but it has a reputation of a poor prognosis and high mortality rate. This study examined a group of cases with a known predisposition to AP to search for variables that were associated with the presence of AP and survival in affected dogs.

Dogs diagnosed with megaoesophagus between 01/01/97 and 01/10/07 were identified from clinical databases at Glasgow University Veterinary School and reviewed. Cases without visible oesophageal dilation, clinical signs of dysphagia or where oesophageal dilation was only identified under general anaesthesia were excluded. AP was defined radiographically as the presence of an alveolar pattern or consolidation of ventral lung lobes. Data collected included signalment, historical, clinical, laboratory and radiographic findings, date and cause of death. Owners and referring veterinarians were contacted for follow-up data. Categorical data was analysed using either Fisher exact or Chi Square tests. Continuous data was analysed using Wilcoxon rank sum tests.

Eighty-nine cases fulfilled the inclusion criteria, of which 34 (38%) had AP at the time of diagnosis. Cases with AP were less likely to; be lighter (P = 0.02), have segmental oesophageal dilation (P = 0.04), have hyperglycemia (P = 0.026), or to survive to discharge (P = 0.004) than those without AP. AP was associated with abnormal lower respiratory tract noise (P = 0.03), higher median total white blood cell counts (P = 0.008) and median segmented neutrophil counts (P = 0.003).

At the time of censorship, 29/34 (85%) of cases with AP were dead. Amongst the dogs that died, 15/29 (52%) were euthanised because of AP. Ten of these cases died or were euthanised before discharge. Dogs that died of AP were more likely to have had oxygen therapy (P = 0.007), been in the intensive care unit (P = 0.007) or had antibiotics prior to diagnosis (P = 0.02). Presence of lung lobe consolidation and extent of the radiographic changes were not found to be significant.

This study suggests that smaller patients, and those with segmental oesophageal dilation (e.g., vascular ring anomalies) may have a reduced risk of developing AP. In a population of dogs with megaesophagus, the presence of AP adversely affected short term survival, however 50% of patients with AP did survive to discharge. These are likely to be the less severely affected patients that do not require intensive care and oxygen therapy.