KEY FACTS Canine Pyothorax : Clinical Presentation , Diagnosis , and Treatment

Clinical presentation of canine pyothorax can be delayed and nonspecific. Fever, dyspnea, and weight loss are the most common physical examination findings. Diagnosis is made with radiographic findings and analysis of aspirated pleural fluid. Pleural infections have a high prevalence of polymicrobic infections. Antibiotic therapy without drainage and lavage is ineffective for pyothorax. Excessive delays in treatment can result in serious pulmonary dysfunction and may necessitate surgical intervention. Prognosis for canine pyothorax is fair to good with early diagnosis and aggressive medical and/or surgical treatment. Pyothorax is an uncommon but important disease of dogs. Inflammatory conditions of the pleura and pleural space lead to alterations in capillary permeability and lymphatic function. An increase of septic fluid within the thoracic cavity leads to pulmonary dysfunction and systemic illness. This article discusses the clinical presentation, diagnosis, commonly isolated bacteria, proper treatment and management, and prognosis of canine pyothorax. SIGNALMENT, HISTORY, AND PHYSICAL FINDINGS In dogs, pyothorax most commonly occurs at a mean age of 3 to 4 years (range: 1 to 11 years). However, the first case report of pyothorax in a canine neonate was recently reported. Several studies show a male:female ratio of 2:1, whereas other reports have shown no sex predilection. Typically, medium to large breeds are affected, and affected breeds may differ on geographic location. Although no single breed predominates, dogs of the hunting/working type are overrepresented. An increased prevalence of grass awn cases were seen in springer spaniels, Labrador retrievers, golden retrievers, Brittany spaniels, and Airedale terriers. Most cases occur during the fall and winter, coinciding with training and hunting seasons. Most dogs with pyothorax present with signs referable to accumulation of pleural effusion. Signs ensue because of decreased lung expandability and impaired gas exchange. Although some cases are insidious and nonspecific and CE 180 Vol. 25, No. 3 March 2003 n Working dogs appear to be more predisposed to developing pyothorax secondary to grass awn migration. n The diagnosis of pyothorax is made by cytologic evaluation and culture of pleural fluid. n Eighty percent of specimens from dogs with anaerobic infections contain both obligate anaerobes and aerobic bacteria. n Mortality is higher in patients treated with multiple thoracocenteses and antibiotics than in those treated with tube