Page 347 - Clinical Small Animal Internal Medicine

32 Pulmonary Thromboembolism 315

Clinical signs consistent with PTE
VetBooks.ir No known predisposing condition Known predisposing condition

Has investigation of underlying Thoracic radiography
disease been undertaken?
No
Consistent with but Normal Consistent with other disease Definitive for PTE:
not definitive for PTE Regional oligemia
Westermark sign
Arterial BG
Yes CBC/Chem/UA
Echo/Abdo US/LDDT analysis Other appropriate diagnostic tests
Arterial BG analysis
Hypoxemia Normal Diagnose
Hypocapnia Treat PTE
No Alternative Predisposing High A-a gradient accordingly
predisposition diagnosis condition
identified made identified
Echocardiography
D-dimer or
TEG or Treat
AT Level accordingly
D-dimer or
RVOT/PA RV dilatation Normal TEG or
Thrombus RV hypokinesis AT Level
Septal deviation
Pulmonary hypertension
High D-dimer Normal D-dimer
Normal D-dimer High D-dimer
or or Diagnose or or
Normal TEG Hypercoagulable TEG PTE Hypercoagulable TEG Normal TEG
or
or
or or
Normal AT Level Reduced AT Level Reduced AT Level Normal AT Level
Treat
symptomatically
V/Q Pulmonary CT pulmonary
Treat Scanning angiography angiography
symptomatically
Normal Consistent with other disease
Diagnose
PTE
Treat Treat
symptomatically accordingly
Figure 32.1 A possible diagnostic algorithm for the investigation of small animals with suspected PTE.
Patients at high risk must be identified for expedited Initial Diagnostics
diagnostic evaluation. A possible diagnostic schema for
small animals is proposed in Figure 32.1. All patients Survey Thoracic Radiography
Up to 30% dogs with PTE have normal thoracic radio­
with consistent clinical signs should undergo thoracic graphs, but most small animals in the literature with
radiography, ideally in combination with arterial blood confirmed PTE had abnormalities visible. This finding
gas analysis. Occasionally, thoracic radiography will be might reflect an inability to detect small emboli, as
diagnostic but most patients will require additional abnormal thoracic radiographs might only occur in
tests, particularly if arterial blood gas analysis is con­ severe PTE. It has therefore been suggested that PTE
sistent with PTE. Echocardiography is a reasonable should be suspected in all markedly dyspneic patients
next step. It is noninvasive, can be performed bedside, with normal thoracic radiographs. Similarly, where risk
and eliminates key differentials, clarifying which factors are present, PTE should be considered as the
patients require advanced imaging. Cardiac biomarkers cause of unexplained pulmonary infiltrates on thoracic
may also contribute to decision making. In patients radiographs.
with clinical signs but without known risk factors, Various radiographic abnormalities can be seen in
coagulation testing with D‐dimers, antithrombin (AT) PTE. Pulmonary infiltrates are the most common
activity, or thromboelastography (TEG) may help finding and are typically alveolar or alveolar‐interstitial
identify patients with evidence of thrombin activa­ in appearance, present focally or multifocally. These
tion, AT depletion or hypercoagulability, respectively. infiltrates likely represent edema, atelectasis, hemorrhage
Recognition of a dyspneic, hypercoagulable patient or infarction and often have indistinct borders.
should prompt reevaluation for predisposing condi­ Hypovascular lung areas are hyperlucent regions
tions and mandates imaging studies for PTE.