IS he peeing at all? Straining to pee can be Urinary Calculi. Is he straining, hunched up or peeing in a drizzle as opposed to a stream? The calcium/phosphorous ratio everyone else expressed concerned about will cause this. If they have not had tetanus vaccine that could be it too.
This sounds like UC to me. If it is he needs treatment FAST. Give him ammonium chloride in a drench, 1 teaspoon per 75 lbs of body weight in 20 cc of water every 12 hours for two days, then 1/2 teaspoon every 12 hours for 3 days. This treatment may not work and if so surgery is his only option. If you cannot get Ammonium Chloride fast, use Fruit Fresh (in the canning area of the grocery store) until you can. This is very serious and if not treated quickly he will die.
If you suspect tetanus he needs the tetanus antitoxin- not the vaccine. Once symptoms have set in it is too late for the vaccine. He will need to be vaccinated in three weeks after giving the antitoxin. I highly recommend CD&T vaccines for all goats.