A kidney stone is a solid mass that is formed by the separation of certain substances from the urine in a kidney. Most kidney stones are composed of calcium oxalate, but uric acid and other crystals are also possible. If the kidney stone remains extremely small, or if it does not move from the kidney, it may not cause any trouble. The problems occur when it moves in such a way that it blocks the flow of urine through the tube leading from the kidney to the bladder. This tube is called the ureter.

The most common early indication that a person has a kidney stone is a severe pain between the lower back and side. This is not usually a dull ache. It is a sharp, localized pain that may come in waves. The pain typically does not change with body movement or position. This pain can be caused by the pressure exerted by the backup of urine behind the stone or the contractions of the ureter as it tries to pass the stone. Kidney stone sufferers often try, unsuccessfully, to get comfortable and may pace around the room trying to get relief. The pain is often severe enough to cause nausea, and even vomiting. 

Another common sign of a kidney stone is visible blood in the urine. The blood is caused by the stone damaging the walls of the kidney or ureter as it moves. This can be seen as a darkening of the urine and may be more of a brown color than red. The darkened urine can occur before the pain begins and may be an early warning of what may develop.

If a kidney stone continues to move, the pain it causes will usually move with it. This is a strong indication that the pain is not due to one of the other causes mentioned earlier. As the stone moves through the ureter, the sensation can be tracked around the side, from back to front, until the stone is deposited in the bladder.

Along with these symptoms the person may complain of cramping in the kidney area or pain while urinating. If several of these symptoms are present, it is reasonable to assume that a kidney stone is present.