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by Kristine McComis
Shadow is a 10 year old male castrated retired racing Greyhound that presented to the Veterinary Hospital with severe pleural effusion, dyspnea, and a suspected middle lung lobe mass. The owners had noticed the dog’s shallow breathing during the night and took Shadow to their primary veterinary the next day. The referring veterinarian performed radiographs and ultrasonography that suggested the pleural effusion and a possible mass in the middle lung lobe. An EKG showed atrial fibrillation. One and a half liters of dark red watery fluid was removed from the thorax on two consecutive days. Shadow’s appetite decreased although he was drinking a lot of water.
The dog was admitted to The Ohio State Veterinary Hospital on October 26, 2009 for diagnostic evaluation by Dr. Guillermo Couto, professor of Oncology and Hematology. As is often the case, neither echocardiography nor thoracic radiographs revealed a definitive cause for the pleural effusion. Cytologic analysis of the fluid showed reactive mesothelial cells, another non-specific finding. Unfortunately, Shadow’s owners were in the difficult position of knowing that their dog had a serious problem, but did not have adequate information to make decisions on therapy. Dr. Couto consulted with Dr. Christopher Adin, assistant professor of Surgery. Traditionally, exploration and biopsies of thoracic structures were performed through thoracotomy incisions. In dogs without a localized etiology, median sternotomy was required for examination of both hemithoraces. More recently, thoracoscopic surgery has revolutionized the ability to perform exploration of the thorax using minimally invasive techniques. In Shadow’s case, veterinarians determined that thoracoscopic exploration would provide an excellent view of the thorax, as well as a method for obtaining biopsy samples from the pleura, lung and any masses that may be detected on direct examination.
The following day, thoracoscopy was performed, revealing a two centimeter mass on the sternum and a mass on the pericardium, which had not been seen on the ultrasound or radiographs. The masses were consistent with mesothelioma. Several other nodules and white plaques observed throughout the pleural cavity. The mediastinum was opaque and appeared thickened. Multiple biopsies were obtained to confirm the diagnosis. Two pleural ports were placed during surgery, one on each side of the chest. The pleural ports would provide a method for easy withdrawal of the pleural effusion after surgery, and would also provide a means of instilling intracavitary chemotherapy. Shadow was placed in the ICU, with a chest tube and needed oxygen. He remained comfortable post-surgery. Shadow was released on October 30th when his respiratory rate was within normal limits without supplemental oxygen. His owners were instructed on how to drain the thoracic fluid from the ports. We recommended chemotherapy to reduce the production of pleural fluid to help him breathe better, but unfortunately, the mesothelioma was not curable.
Although Shadow did not respond well to the chemotherapy and experienced continued pleural effusion, his owners were extremely appreciative that they were provided with a rapid diagnosis with minimal discomfort experienced by their beloved pet.