Good to hear your GP is on top of it. Of course I'd also make sure your Rumy knows about it.
I've done more 24hrs than I can count, and others have pretty much said what needs to be said about them. My first was when I was showing some blood and protien in my urine tests (I had not been diagnosed with Lupus yet). If you're showing some protien it's not a reason to panic, but it is something to keep a close eye on. In my case I did develop nephritis (and it's how I FINALLY got a diagnosis). Other things to watch for in nephritis is retaining water (as Joan mentioned) and raising blood press. When my nephritis is at it's wost my BP will go VERY high and I turn into a big water balloon (I know I'm in trouble when my feet swell up!).
I don't want to scare ya with the treatment for nephritis, hopefully you just have a small spike and it'll go away, that even happens with me on occasion. But my first bout of nephritis was 15 years ago and I had a second problem with it a couple of years ago. Both times I responded very well to treatment. But it is important to keep a close eye on it. When my Kindeys get involved I can go downhill very fast. First time it took too long to figure out what was happening and my condition was horrible. Second time we knew what was going on and caught it before I even really had noticed things were getting bad, although my Doc. still says my second infection was worse than my first.
Feel free to contact me in the future if you end up with any questions on nephritis, it's a beast I know well. Hopefully your 24 will come out clean, odds are it will.
Best Wishes,
Eric