This happened to us on January 14 2010 with our 12 year 8 mo old golden Barkley. His diagnosis: hemangiosarcoma.

Please, if your vet didn't do x-rays of your dog's spleen, get xrays taken as soon as possible. Also, get a red blood cell count.

I hope you find the cause of the collapse. Having been in your shoes, I sympathize with what you are going through right now.

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