after being ridden. He seems to be swollen on the right inner thigh and over onto his sheath. Has anyone else seen anything like this? He was better when on antibiotic for a skin thing, but vet doesn’t want him on long-term antib’s without finding out what the problem really is. Vet is going to do a more in-depth work up this weekend. Any ideas other than “an infection”?
Well it is probably too late in the year for fly bites where you are. But could there be some kind of irritation that is aggravated by sweat when riding? Is the swelling there when he is at rest?
Is he blanketed with leg straps? Maybe an allergy. Maybe getting rubbed while laying down.
Since the antibiotics masked the condition it sure sounds infection/irritation related.
My horse will do the same thing when you scratch near his naval or on the inside of his thigh. Looks pretty interesting, as you say, a 17hand dog lifting his leg. 
His is caused by little tiny fly bites on that oh so tender skin. The sweat really makes a difference.
“The older I get, the better I used to be, but who the heck cares!”
Flys are never really a problem, but I’ll ask about the leg straps. It seems to be inflamed before he gets ridden as well as after. I did look for those tiny fly-bite bumps but didn’t see anything.
There were these tiny, bugs that you could not see that were in the bedding and drove the horses nuts!! 
We had to bed the stalls deep and pick out the droppings constantly rather than do any digging and stirring up these awful bugs. 
EEWWW! I’ll check the shavings. If there are bugs in there, the barn owner will have the supplier out there loading them up before them know what hit them. She makes the hay supplier come unload full semi loads of hay from the loft if there is something wrong with it. She checks each load before it goes into the loft, but we had one load with stickers in it that hurt some horses’ mouths, so she sent the whole load back.
Could it be an umbilical hernia?
My gelding got one and had a huge ugly swollen lump on his belly…pretty close to the sheath area. I think these are pretty common and so your vet would be able to diagnose it right away.
It’s a long shot…but could your horse possibly be a “rig”? Maybe one testicle has not descended and is causing irritation. It happened to a friends horse some years back. Even though he was vet inspected and his papers said he was gelded in Germany. They lied. A few years later there were problems with swelling and soreness in that exact area. Not sure how the diagnosed him, but he had to be re-gelded on that one side. He was fine ever since.
after being ridden. He seems to be swollen on the right inner thigh and over onto his sheath. Has anyone else seen anything like this? He was better when on antibiotic for a skin thing, but vet doesn’t want him on long-term antib’s without finding out what the problem really is. Vet is going to do a more in-depth work up this weekend. Any ideas other than “an infection”?
Good ideas, Chef and Robbierox. I’ll pass on the suggestions. It’s not my horse, but the girl aways rides after I do. I’ve wondered if there wasn’t a testicle floating around up there, since this horse can get quite aroused waiting at the back gate. I had thought that it was an obvious thing to look for and had probably been eliminated.
Give him a good cleaning. You know where.
Use the Force.
Every crevice has been cleaned. The very upper part of the sheath looks kind of swollen, as does the top inside of the leg. They sedated him for the cleaning so it could be thorough, even though he seems to be happy to be touched in that zone.
