What is a Kidney Stone?
The medical terminology for kidney stones is Nephrolithiasis or Renal Calculi. A kidney stone is a solid lump (from as small as a grain of sand to as large as the size a golf ball) made up of crystals that separate from urine and build up on the inner surfaces of the kidney. The Herring Lab's (a major analyzer of kidney stones) web site has close up photographs of various types of kidney stones
Illustrations courtsey of Blausen.com staff. "Blausen gallery 2014". Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
Kidneys are fist-sized bean-shaped organs located near the middle of the back with one on either side of the spine just below the rib cage (see illustration showing location). They filter the blood collecting about two quarts of waste products and excess water (urine) each day. Normally this flows out through tubes (ureters) that connect each kidney to the bladder, and then on out through the relatively short tube leading from the bladder to outside the body (urethra).
But when too little water is available to dilute the waste products, these may stay in the kidney and form solid pieces of material that can continue to grow as additional material builds up forming a kidney stone which can be smooth or lumpy or jagged and sharp in shape. Most are small like a grain of sand or rice, but some are larger like a pearl or even as large as a golf ball.
Kidney stones will usually go on undetected ... until it breaks loose and tries to travel down the urinary tract. If the kidney stone is small enough, it might pass all the way out of the body without too much pain. But a larger kidney stone might get stuck in one of the relatively long and small diameter ureters, in the bladder, or in the urethra causing extreme pain in your back or side that will not go away. Sometimes the stuck stone can even stop the flow of urine which, also, causes intense pain.