Hello, my name isXXXXX and I have over 20 years of experience as a veterinarian.
I am very sorry that Chulo has bleeding from his penis for the past couple of days.
There are many reasons to have blood in the urine or bleeding from the prepuce.
We often think of an infection but also crystals or stones in the urinary tract, masses on the penis or prepuce or in the urinary tract or clotting disorders are possible causes. If he is an un-neutered male then prostatic cysts or abscess or a prostatic tumor are possible causes as well.
Are his gums and tongue white, pale pink or bubble gum pink? If they are nice and pink then he likely hasn't lost enough blood to make him anemic and that is a good sign.
Is he bleeding only when he passes urine (is he constantly straining and dribbling urine) or does the bleeding seem independent of passing urine?
If the bleeding is when he passes urine then concerns would be a genitourinary tract infection, crystals or stones in his urinary tract, a clotting abnormality or a mass in his urinary tract.
If the bleeding is independent of him passing urine the concerns would be trauma to his penis, a mass in his prostate, prepuce or on his penis, or a clotting abnormality.
You can try to gently retract his prepuce over his penis to look for a mass or cut either in his prepuce or on his penis. If he hasn't been neutered and his penis and prepuce look normal he may have prostatic disease. If you can see a mass or a cut on his penis or prepuce then a cold compress on it, followed by gently it patting dry and then applying some corn starch or flour to help form a clot may stop the bleeding.
If he doesn't have a visible mass or cut and he were my patient I'd start with a urinalysis with culture and radiographs of his abdomen to look at his kidneys and bladder for signs of stones and the size and shape of his prostate. If he had pale gums signifying significant blood loss then I would want to check his clotting function too.
If money was very tight and there were signs of infection on the urinalysis then an antibiotic prescription for 10 days would be reasonable to start. Certainly because he has a history of spinal pain it is possible that he hasn't been fully emptying his bladder and that can predispose to infections.
If I saw lots of crystals or abnormal looking cells on the urinalysis I'd warn the owner that things may be more serious.
And I'd recommend a recheck of his urine at the end of the antibiotic therapy. If there was still blood then radiographs or an ultrasound of his bladder/kidneys is needed.
If this is a prostatic infection and he hasn't been neutered I highly recommend that be done once he feels a little better.
All you can do for him at home is encourage fluid intake to flush out his urinary tract. Add water or low salt beef or chicken broth to his food or feed him canned food to encourage eating and increase his fluid intake
Give him ice cubes. Offer him fresh water frequently.
And make sure he gets out frequently to urinate.
If he is straining but unable to pass urine, is vomiting, runs a fever (more than 103F rectally), has a tense, painful abdomen with gentle pressure, or his gums become very pale it is time for emergency veterinary care.
Let me know if you have any further questions.