Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 15 years of experience. I look forward to working with you.
I am so sorry he is experiencing this! There are several possible causes for what you have observed. It is probably not parasites, though. That would be highly unusual. There is one rare kidney worm but when you see "strings" they are usually mucous strings and not parasites. For bloody urine and inappropriately urinating in odd spots this could be due to an infection (bacterial, yeast), crystals in the urine, bladder/kidney stones or cystitis (which may not be related to an infection but instead could be stress related).
Should he be seen? Yes, I recommend you have him seen as soon as possible, especially if he is having any frequency to urinate and/or any straining when urinating. IN our male cats they are at higher risk for urinary blockage (urethral obstruction) which can occur not only due to debris in the urethra but also just due to swelling from straining. If he gets blocked, not only is this life threatening, but also this can be very expensive to treat, requiring hospitalization and sometimes surgery. So, my best recommendation is have him seen ASAP. If you can have him easily seen tonight then that would be in his best interest. If you cannot have him seen tonight, then encourage him to drink, make sure his litter box is clean/fresh and watch him closely; try to get him in first thing tomorrow to be seen. Signs this has progressed to urethral obstruction would be straining to urinate without producing any urine and/or painful abdomen/stomach or sometimes vocalizing while urinating.
As far as the drugs you have at home, unfortunately I recommend you give the burprenorphine. This can help tremendously to relax him (prevent straining) and perhaps alleviate pain. This is a great drug for this problem but not a long-term solution (doesn't treat the issue but helps him feel better).
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