The kidneys are responsible for filtering the blood and excreting waste products and excess water in the form of urine. They also control the body’s acid/base balance so that when blood and body fluids are too acid or too alkaline, the acidity of the urine is altered to restore the balance.
Kidney stones are quite common, particularly in middle age. They are usually caused by excessive concentrations of various substances, principally calcium; a lack of inhibitors of crystallization in the urine; urine that is too concentrated; or an infection. The calcium and uric acid crystallize into small lumps in the kidneys or the ureters (the tubes that carry urine to the bladder) and are known as stone.
Stones rarely cause pain while in the kidney, but can be agonizing when they become dislodged and start to travel down the urinary tract, or get stuck in it. When this happens, there can be bouts of extreme back pain in the kidney region which sometimes spreads to the abdomen and genitals. Other symptoms include pain on passing urine, and occasionally blood in the urine.