I went riding on a short (45 minutes) ride on my pony today, and he seemed fine and quite happy during the ride. After I got off however, he went in a position to pee and stayed for about 45-60 seconds without urinating. When it did come out, it was thin and there wasn't much. He has never had trouble urinating before, so I checked his genitals (he's a gelding) and it looked very swollen. I didn't actually see his penis so I can't tell you what it looked like. He didn't seem in any pain as I rode him, nor when I prodded his groin. Because I don't own him, and his owner never calls the vet unless absolutely necessary (in which case he will probably have the animal put to sleep) I cannot ask a vet yet . Is this a very dangerous or urgent problem? Is it likely to clear up by itself in a couple of days? I only see him once a week, so I don't know how long he has been swollen. He lives outdoors in some fields with about 10 other horses, a donkey and a llama.
Any advice would be helpful. Thank you!