I believe it was temporary discomfort due to having too much magnesium in your system throw off calcium and other electrolytes. So no worries there! :)
My research on kidneys has shown that skin food is very very helpful. Nourishment is KEY for kidneys! they're like extra-delicate skin, they even have pores for filtering blood, and these need to be protected. the best way I've found for doing that is raw milk. It has to be raw, not pasteurized, not homogonized. Otherwise drink fermented like kefir, yogurt. Take cod liver oil too and make sure your zinc intake is normal.
if you have problems with your urine stream being weak, or frequent urinatino, then you need to do some cleansing first. Cranberry juice is great for that. Drink a couple glasses a day for 3-5 days. Mild diuretics include parsley and dandelion and nettle. If there's irritation or infection still after the cranberry juice, then you need uva ursi and marshmallow. If you suspect you have stones (lots of mid-back pain and painful urination plus sore spots on the soles of the feet corresponding to kidneys) then you need to take stone dissolvers such as liquid phosfood, apple cider vinegar, and herbs.
Hope that helps! :)