SMALL ANIMAL MEDICINE
Table 1: Conditions predisposing to aspiration of gastric content
Large volumes of
intragastric content Oesophageal
disorders Impairment of
protective airway
reflexes Impaired
consciousness Others
Delayed gastric
emptying Oesophageal
obstruction Airway trauma Sedation/
general anaesthesia Nasogastric/
gastric intubation
Pyloric outflow
obstruction / Bowel
obstruction Oesophageal
dysmotility Laryngeal or
pharyngeal
dysfunction Head trauma Foreign body
Gastrointestinal
motility disorders Megaoesophagus
(various causes) Seizures Ileus Reflux oesophagitis Encephalopathy Cleft palate
Pain Achalasia Coma Weakness,
paresis, paralysis*
Opioid administration Gastroesophageal
sphincter
incompetence
Tracheostomy
Metabolic
derangements
Recent consumption
of a meal
Anxiety/
pregnancy/obesity
Physical examination findings that may be found in
patients with AP are lethargy, tachypnoea, dyspnoea,
fever, coughing and abnormal lung sounds on
thoracic auscultation. However, in a study looking at
125 dogs with aspiration pneumonia, only half of the
dogs presented with tachypnoea and fever and less
than half of the dogs had a cough and /or abnormal
lung sounds.
Further diagnostic tests such as haematology may be
helpful as it is an infectious disease so the white blood
cell count is expected to be increased with a possible
left shift. But not all patients with AP will have these
changes as the patient’s immune response, the phase
of infection and the severity of the infection will alter
the white blood cell concentration. No significant
findings are usually noted on regular biochemistry.
C-reactive protein (CRP) can be used as a biomarker.
A study found that dogs with bacterial pneumonia had
significantly higher CRP concentrations compared to
dogs with other respiratory diseases. In this study they
found that they could rule out bacterial pneumonia in
dogs with clinical signs lasting > 24 hours with a CRP
of <20mg/L. If the CRP was found to be > 100mg/L
with clinical signs that had lasted for >24 hours, a
diagnosis of bacterial pneumonia was very likely.
Thoracic radiographs should be performed in all cases
suspected of having AP. Ideally three views should be
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taken. In early cases, changes may be interstitial in
nature, but the most common findings will be alveolar
infiltrate, in the right middle lung lobe. The next most
commonly affected lung lobes are the right or left
cranial lung lobes, while in more severe cases all lung
lobes can be affected. Bronchoalveolar lavage (BAL)
or transtracheal wash (TTW) findings may also aid
in diagnosis and enable a sample to be obtained for
culture and sensitivity, but in severely compromised
patients it is not always possible to perform either of
these procedures safely.
Several risk factors for aspiration pneumonia have been
identified (Table1). These risk factors vary between
species, but general anaesthesia, vomiting disorders
and megaoesophagus are the most common causes
in dogs. In a study looking at the risk factor in dogs, it
was shown that if a patient had 2 or more risk factors,
they were at a significantly higher risk of developing
aspiration pneumonia. By recognising these risk
factors, and making an effort to manage or minimise
them, the incidence of aspiration pneumonia can be
reduced.
Patients with gastrointestinal disease should be treated
with prokinetics and antiemetics to help reduce the
risk of aspiration of gastric content. Puppies with
parvo virus tend to be at a greater risk of AP due to the
severe ileus the disease causes. These patients need