Yes, it does blow us up like parade balloons doesn't it?!? Maybe you've seen me in the Macy's parade - Goofy? I've had swelling all over sometimes, with no change in diet, meds or activity. Then, I've had swelling in just my hands or my feet or feet and legs. My feet can swell so much I might as well buy footballs, slice 'em open and wear 'em.
Did you ask your doctor what the particular cause might be? Has he or she seen it when it happened? Sometimes they don't quite get it unless they see it so it's a good idea to take photos and make copies. Save a set for your private files and give a set to your doctor. I've found that pictures really can speak louder - or more beliveably - than words, when our symptoms are beyond their understanding.
Just the other day my doctor - not even a specialized lupus doc but the best one I've had - said, "Medicine is more about questions than answers; no doctor knows everything and none of us are always right. There's a lot of guesswork". So, anything we can do to help them 'get the picture' will be a plus for us.
Hoping you'll feel well and won't swell!