Urinothorax in a Quarter Horse filly

An 18 h old Quarter Horse filly, while being treated for diarrhoea, was evaluated for a distended abdomen and electrolyte abnormalities. Peritoneal and pleural fluid was detected by ultrasound and a presumptive diagnosis of a ruptured bladder was made. Intravenous fluid therapy was instituted to correct the electrolyte abnormalities prior to surgical repair of the bladder tear. Anaesthetic complications included hypoxaemia and decreased compliance secondary to the pleural effusion; therefore, a thoracocentesis was performed. Analysis of the pleural fluid revealed a pleural fluid to serum creatinine ratio of >1.0, indicative of urinothorax. The filly recovered from anaesthesia and was discharged on systemic antimicrobials. Urinothorax should be considered in cases of uroperitoneum with concurrent pleural effusion. Early detection may decrease patient morbidity and anaesthetic complications.