Kidney stones are hard, solid particles that form in the urinary tract. In many cases, the stones are very small and can pass out of the body without any problems. However, if a stone (even a small one) blocks the flow of urine, excruciating pain may result, and prompt medical treatment may be needed.
Urine is formed in the kidneys. The kidneys filter out fluids and waste from the body, producing urine. As the urine passes through the kidneys, it becomes more concentrated. From the kidneys, urine flows through thin tubes called ureters into the bladder. The bladder's stretchy walls expand to store the incoming urine until it leaves the body through a tube called the urethra.
The two kidneys are located deep behind the abdominal organs, below the ribs and toward the middle of the back.
|Click the icon to see an image of the urinary tract.|
Types of Kidney Stones
Occasionally, high levels of chemicals in the urine form into crystals. Eventually these crystals become large enough to form stones in the kidney, a condition called nephrolithiasis. Stones (calculi) may also form in the ureter or the bladder. Combinations of minerals and other chemicals, some derived from a person's diet, make up the salts in these stones.
Review Date: 06/08/2010
Reviewed By: Reviewed by: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.