Serial evaluation of clinical, functional, and structural pulmonary changes in 10 dogs with leptospirosis

Abstract Background Leptospirosis is a worldwide zoonosis with multisystemic consequences, including the pulmonary hemorrhage syndrome associated with a high mortality rate in dogs. Hypothesis/Objectives Serial assessment of clinical, functional, and structural pulmonary changes in dogs with acute leptospirosis during the first 8 days of hospitalization. Animals Ten client-owned dogs diagnosed with leptospirosis. Methods Prospective, descriptive case series with daily clinical examination, arterial blood gas analyses on d1-4, d6, and d8 and thoracic computed tomography (CT) with pulmonary segmentation and lung densitometry analysis on d1, d4, and d8. Results Clinical respiratory impairment was observed in most dogs during the measurement period, including 1 dog with fatal pulmonary hemorrhage. Half of the dogs showed hypoxemia (arterial partial pressure of oxygen: median, 56.6 mmHg; range, 49.6-67.8 mmHg) with increased alveolar-arterial PO2 gradient (A-a gradient) (37.9 mmHg 21.9-405.4 mmHg) over the study period. Alveolar ventilation was only minimally affected (arterial partial pressure of carbon dioxide 35.2 mmHg 25.9-42.1 mmHg). Quantitative CT analyses identified increased mean lung attenuation (MLA) in all dogs initially (−612 HU −475 to −681 HU) with progressive improvement in most dogs (d4: −646 HU −583 to −746 HU; d8: −709 HU −624 to −811 HU). Whereas clinical score and CT changes improved progressively in most dogs, the blood gas results showed a fluctuating pattern. Conclusions and clinical importance The clinical pulmonary manifestations of these dogs with leptospirosis were characterized by hypoxemia, increased A-a gradient, and increased lung density. The clinical course seemed to more closely parallel the structural changes observed on CT rather than the functional alterations assessed with arterial blood gas analyses.