I started researching my wakening to Back/kidney area lameness in the morning hours. I first dismissed this to activity of prior day...I'm on my feet alot at work...cement floors. I will have to take a moment sitting up to relieve the pain, and once gone...its gone for the 24 hour period to return after a nights sleep. This doesnt wake me that I know of, as others say happens to them, but any worse it would.  So, interesting to see so many people with these symptoms also have an acid reflux issue. I consider mine moderate, and take prilosec once a week..and several antacids in between(tums).
       Please post if this is your case and may relate the two also...it can only help answer what so many on here are experiencing. Each person seems to get a clear bill of health otherwise..and are baffled.