I have kidney disease and am on pred for that. I had some swelling prior to that b/c of the disease but since being on the pred, my calves ankles and feet really swell up and there is not much I can do to keep the swelling down. I take a diuretic but, I don't take much b/c I need to give my kidneys a rest and chance to heal.
If I have a lot of salt, they really swell up, so talk to the Doc about
a low salt diet and keeping the legs elevated. Also, i'm not sure if they can drain the fluid, if it gets real bad.
Also, may be good to have a urinalysis to check for protiens in his urine (why not at this point), that could be a kidney disease if there are proteins. Edema is a symptom of kidney disease.
So yes, the pred made me swell and someone posted here the other day that they got swollen from pred too.