Ask a Dog Vet and Get Answers to Your Dog Veterinary Questions
I am sorry to hear you are worried about your dog. My name is Rebecca. I am a veterinarian and will do my best to help.
How old is he? Is he neutered?
Blood from the penis can indicate a bladder infection, prostate problem, injury to his penis, or (if he is not neutered) benign prostatic bleeding. If he were mine, I would begin with a urinalysis to check for infection and I would feel his prostate (internal exam through the rectum). I would push the penis out of its sheath to look for a cut or bruising.
If he is not neutered, and this is benign prostatic bleeding, neutering him will stop the problem. If it is a bladder infection, a course of antibiotics should stop the blood.
Let me know if this is helpful, and if I can answer anything else.