Urinary calculi is a threat to wethers especially, since a wether's urethra is smaller than a buck's due to castration. In addition, bucks spray themselves with their urine, which tends to dislodge small, forming stones.
The leading causes of UC are as follows:
Diet: A goat's diet should have a calcium/phosphorus balance of 2:1 or 3:1. When a goat's diet doesn't have this balance, it can cause stones to build up in a buck or wether's urethra. A simple, balanced diet is the key for male goats.
Adding ammonium chloride to their food and/or minerals can help prevent the buildup of stones, as well as adding Apple Cider Vinegar to their water, as long as they'll drink it.
Grain is a primary culprit behind urinary calculi. Most wethers and bucks do not need grain. Working/pack wethers may need some grain to replace the calories they are burning. For that, I would suggest talking to a pack goat owner and asking what grain mixture they use. Whole grain is usually safer than pelleted grain. Bucks may need grain during rut, as rut puts their body through a lot of stress. Apart from these exceptions, I personally feel it isn't worth the risk to feed pelleted grain to male goats.
Hereditary: Sometimes a buck's urethra is shaped oddly inside, and that trait can be passed down and is more prone to UC.
Age of wethering: When a kid is neutered very young, his urethra may not grow as well. The pizzle detaches from the urethra when the buckling hits puberty at 8 weeks, and the pizzle is usually where stones are trapped in dietary cases of Urinary Calculi. However, even when goats are neutered young, with the proper diet they are much less likely to develop stones. Age of wethering is more of an issue in market wethers who are fed a large amount of grain to be competitive in the show ring.
EDIT: It came to my attention that some links I had on here expired. For the best article and treatment method I've been able to find for urinary calculi, I recommend Tennessee Meat Goat's article, "Urinary Calculi in Goats."