I have linked an occasional sudden onset of lower back pain to my kidneys. I have discovered two things that will cause my lower back to suddenly start to ache.
1. Dehydration. I tend to drink a lot of caffeinated black tea during the day and probably not nearly enough water to make up for the dehydrating tea. Occasionally my lower back will start to ache if I've had too many cups of tea, which is my signal to hydrate quickly! If I drink several glasses of water over the course of an hour, my lower back pain will go away within an hour or two.
2. Certain supplements. I bought vitamin d3 made from lanolin last week and started back on 8,000 a day after throwing out my d-3 that contained cod liver oil (see my post on the vitamin d page). However, my kidneys aren't liking the lanolin! Again, a sudden onset of lower back pain about an hour after taking the d3. It took longer for my back pain to disappear this time. ... at least 12 hours or more with lots of water. I tested the supplements 3x, with a few days in between, and each time got back pain. Yikes! A good kidney cleanse is in order. Lisa, got any good juicing recipes for the kidneys?!