Ask a Dog Vet and Get Answers to Your Dog Health Questions
Hello, this is Dr. Jess. I am so sorry to hear about your dog. It is always heart breaking to lose a pet, but seems unfair when it comes so unexpectedly. I have to agree with your vet's suspicion. The most common cause of a pet dying quickly following a period of heavy breathing and weakness would be a tumor on the spleen or liver that abruptly began bleeding. Did your dog's belly look enlarged at all when you found her? Sometimes dogs can live with these tumors on their liver or spleen (called hemangiosarcoma or hemangioma) for some time while showing no ill effects, then at some point for no real reason, the tumor errodes into a large blood vessel and a massive internal hemorrhage can occur. Usually these dogs present to us with labored breathing and weakness, and it can happen in the course of a few hours.