Though Plaquenil is not used as a
treatment for kidney involvement, I did read an article on the Lupus Foundation of America website that says:
[source link - see #5]
"Clinical research data released in 2008 showed that lupus patients treated with hydroxychloroquine, used most often to treat lupus skin and joint problems, were less likely to have kidney disease, had less severe disease, and required lower doses of corticosteroids than patients who did not receive the drug."
So even though Plaquenil won't treat your kidneys if you're having problems, it seems like a good line of defense for controlling the overall disease activity, like Clare said (I think she said it better than I did, lol).