It hurts incredibly bad on both sides running parallel to my spinal cord. The worst pain is about three inches below my bra line. Right now I am on the first day of the menstruating part of my cycle. I am not sure if it is due to this, a warning sign of renal failure, or a strained muscle from intercourse.
Renal failure is uncommon.
Your kidneys are located out to the sides. If you reach behind you and put your hands flat on your back, that is where they are. There is a chain of muscles along the sides of the spine. In fact, there are several rows, going in different directions. There are hundreds of small muscles in your back.