Quantification and characterization of pleural fluid in healthy dogs with thoracostomy tubes

OBJECTIVE To quantify and characterize pleural fluid collected from healthy dogs after placement of a thoracostomy tube (TT). ANIMALS 8 healthy Coonhound-cross dogs (mean ± SD weight, 27.2 ± 1.6 kg). PROCEDURES Thoracic CT of each dog was performed before placement of a TT and daily thereafter for 7 days. Thoracic fluid volume was calculated from CT images. Effusion was aspirated when detected; volume was recorded, and cytologic analysis and bacterial culture were performed. RESULTS Mean ± SD volume of pleural effusion detected by CT was 1.43 ± 0.59 mL/kg (range, 0.12 to 3.32 mL/kg). Mean volume collected via aspiration was 0.48 ± 0.84 mL/kg (range, 0 to 2.16 mL/kg). Cytologic analysis yielded results consistent with an exudate, characterized by septic suppurative inflammation in 6 dogs and mixed inflammation in 1 dog; there was insufficient volume for analysis in 1 dog. Sufficient volume was obtained for bacterial culture for 6 dogs, which yielded pure growths of Staphylococcus pseudintermedius (n = 3) and Streptococcus equi subspecies zooepidemicus (2) and mixed growth of both of these species (1). The TT was removed before day 7 in 4 dogs because of pyothorax (n = 3) and irreversible damage to the TT (1). CONCLUSIONS AND CLINICAL RELEVANCE Presence of a TT induced a minimal volume of pleural effusion in healthy dogs. Pyothorax developed in most dogs between 4 and 6 days after TT placement. On the basis of these findings, a TT should be removed by the fourth day after placement, unless complications are detected sooner.