Hmm. Wrote a lengthy reply, but don't know where it went. Here goes.
Of the hundreds of thousands(millions?) of calves castrated at an early age, I'd hazard guess that only a tiny fraction of a percentage of them ever have a problem. IMO, it's never been a significant consideration. Yes, early castration may predispose to development of urolithiasis and urethral obstruction in feeder steers that are on a misformulated ration with Ca
ratio closer to 1:1 rather than the desired 2:1; excessive P predisposes to formation of urinary calculi - which are usually kind of like gritty sand to thick toothpaste-consistency material. Rarely have I seen any that were as large as a BB or English pea - but sometimes there may be a double-handful of grit/sludge in the bladder. You'd be surprised at how effectively just a little bit of 'sand' can plug the urethra, though.
In my experience, the vast majority of cases are in steers on a high-grain ration.
I'm not sure anyone has done extensive measurement of urethral diameter in early-castrated steers vs those done at an older age, but I don't necessarily doubt that the early-castrated calves have smaller urethral diameter. One study I recall seeing suggested that bulls and partial- or late-castrated steers were able to expel larger calculi just because they had better urethral muscle development, rather than just a larger urethral diameter.
I have seen an occasional bull/steer calf, on pasture on the dam, develop urethral obstruction and waterbelly - and saw it once in a big, mature ChiAngus bull; I have to think that those cases may have involved silica uroliths rather than the struvite types associated with Ca
imbalance.
Saw a case presentation once, where a snake-oil salesman convinced a feedlot operator to incorporate diatomaceous earth into a feeder ration as a 'natural dewomer' (it's NOT - DE has never killed a worm in an animal. EVER.). They didn't account for mineral content of the DE, and precipitated a big outbreak of urolithiasis, losing a number of steers. Can't recall, at this point, if they were silica or struvite uroliths, but I'd suspect struvite, unless the P content of the DE also skewed the Ca
ratio out of whack.
Wethers usually block, initially, in the little worm-like urethral process at the tip end of the penis; often if you just snip that off, you remove the obstruction and set them right - but if they're early-castrates, you may not be able to extend/exteriorize the penis to get at it.
Had one calf in this fall's crop that I could only find one testicle on - poked, prodded, palpated - just could not find #2. Don't remember which calf it was, but I've been looking at scrotums, and none of 'em show any evidence of one having come down in the 2-3 months since; guess eventually, one will start to look more bullish than his cohorts.