If he can't pass urine at all and is in a great deal of distress, the kindest thing may be to shoot him. Treatment for a bad blockage is very expensive and iffy at best. However, if he can pass at least some urine he may be able to be helped. Go online and google urinary calculi in goats. You may be able to find some helpful information that you can use there.
I'm sorry I cannot be of more help. In the over 40 years I had goats I only had one case of urinary calculi and that was in a buck who was deprived of water for an unknown period. His automatic waterer failed and I didn't notice it right away. By the way, my goats, including my bucks were fed almost exclusively on alfalfa and that one buck was the only case of urinary calculi I ever saw. I fed alfalfa because that is what I could get, but wethers and other non breeding and non milking goats don't need alfalfa. Grass hay will suit them just fine.