Use of the D-dimer Assay for Diagnosing Thromboembolic Disease in the Dog

An 8-year-old, medium-sized, mixed-breed dog is presented to the veterinary clinician with the complaints of excessive panting and exercise intolerance. The dog’s temperature is 101.5 ̊F, and heart rate is 150 beats per minute. Physical examination discloses occasional, soft crackles at the end of the inspiration/early expiration over the right hemithorax, but it is otherwise unremarkable. Thoracic radiographs are normal. The dog is sent home with exercise restriction while awaiting results of a routine laboratory biochemical panel. Two days later, the dog returns with overt respiratory distress and tachypnea. How should this animal be evaluated?