I am sorry to hear you are worried about Shade. I am a veterinarian and will do my best to help.
Is he able to pass some urine, even a little? Or is he straining to urinate but nothing coming out at all?
Is he eating, and drinking?
Cats can be prone to forming crystals in their urine, that is like fine sand. It is irritating, and can make the cat be uncomfortable, and strain to urinate. However, in male cats, these crystals can form a blockage, and the cat cannot pass urine at all. If this happens, he goes into kidney
failure, and dies. The only way to help these "blocked" cats is to put in a urinary catheter to let the urine out of the bladder.
There are special diets that can prevent the crystals from forming, but just feeding moist food
is not enough.
If he is eating, and passing some urine, he may just need antibiotics and anti inflammatory medication. However, these are by prescription so you still need a vet visit.
If he is passing urine, you could, only once, give 1/2 of a baby aspirin for pain and inflammation. Do not repeat it. Do not give Tylenol, or any other type of pain reliever to a cat. If you are not positive he is passing any urine, do not give the baby aspirin.
If this were my own cat, I would not be trying to treat him at home. I would feel the bladder with my hands; if it is big and hard I would be on my way to the clinic to sedate him and put in a catheter. If the bladder is small and he is passing urine, I would give him injections to relax his bladder and urethra, for pain, and start antibiotics.
You can get some of the special diets at Chewy.com, or at vet offices, but not in most pet stores. One is Royal Canin urinary SO diet, another is Hills CD.
Let me know if he is passing some urine, and if he is eating.