I know this post is old now, but I had to chime in. You are definitely not alone. Back in January, our dog suddenly collapsed one night. He could not get his balance, he was crying, and his tongue and gums were turning white. We rushed him to the emergency vet, and they kept him overnight on pain meds. In the morning he was transferred to another vet for more extensive tests. He was bleeding from his spleen. We opted to have the spleen removed and tested. The tragic news came back that he had Hemangiosarcoma. I believe this is what your dog had as well. There is no cure for this, and the prognosis is abysmal. It is 1-3 months without chemo, 3-5 with chemo. We chose not to put him through chemo and let him live out his days. We had only had him for one year, he was rescued from a korean dog farm, flown to the US, and now was given this death sentence. It is completely unfair, what a cruel world. Two mornings ago, he collapsed and showed all the same symptoms as his first bleeding incident. We silently agreed that we knew it was his time. We took him to the vet and they said there was nothing further that could be done. We knew we had to put him down, he was in pain with no cure. I am honestly still in disbelief that he is gone. I wake up in the morning expecting him to be there wagging his tail waiting for his breakfast, at night I expect him to come bolting in my room and nudge the back of my chair for his snack. One of the sweetest dogs I have ever known taken so tragically. I will remember him forever.