Just a comment on part of rosta's post. "I am not too familiar with the Kidney side of things because I haven't gotten to that stage yet". I might just be reading this the wrong way, but just to put your mind at rest, it is not always the case because we have 'systemic' lupus that we will go on to develop kidney problems.
Not all SLE patients have kidney involvement, though it is thought that around 40% of lupus patients do have. Not all of these will require treatment, and some might require aggressive treatment. It depends on the type of kidney involvement a patient has.
Pain in the kidney area can also be an indicator of other things happening. For instance you may have pleurisy, a kidney stone, kidney infection or even a muscular spasm coming from the lower or lumbar spine. Only the pleurisy in this case would have anything to do with lupus. If you do get worried about the possibility of kidney involvement, then you must visit your doctor to have the proper tests carried out if he thinks this is necessary.