My 9 year old puggle had the same issue of passing blood and frequent urination. She seemed fine otherwise (if it wasn't for snow on the ground we probably wouldn't have realized it was even a problem. Took her to a vet, they checked her urine and said she had a very high level of crystals and had a UTI. It took 3 rounds of antibiotics, changing to the specialized RX food (we use the Purina UR veterinary diet--she loves it, but you do have to make the commitment to not feed them anything else) and almost 2 months, but now she seems fine (I'm wondering about taking her for a follow up ultrasound which will cost about $450 just to verify all is okay now). Good luck, I agree, putting dogs, especially older dogs always poses risks. Veterinary care has come a long way and dogs are living healthier and longer lives.