Urine contains a variety of minerals. Normally, minerals in the urine cause no problems, but if they begin to clump together, they form crystals and rock-like deposits known as kidney stones, or renal lithiasis. Stones can get stuck and cause considerable pain as they attempt to pass through the kidney. Kidney stones send half a million people a year to the emergency room, the National Digestive and Urologic Information Clearinghouse (NKUDIC) states.
Calcium Stones
Calcium stones are the most common type of stone; two types of calcium, calcium oxalate and calcium phosphate form stones, with calcium oxalate being the most common. Small calcium stones may pass through the kidneys without difficulty; large stones may need medical intervention to break them up into smaller pieces.
A high amount of calcium in the urine, known as hypercalciuria, or a high level of oxalate, known as hyperoxaluria, can cause stone formation. A diet high in oxalate can cause higher-than-normal urine levels; large amounts of calcium oxalate are found in chocolate, nuts and produce such as rhubarb and spinach. High oxalate levels also occur commonly in people who have had gastric bypass surgery or those with diseases that cause chronic bowel irritation, the NKUDIC explains. Hypercalciuria occurs in people who absorb too much calcium from their bones or intestines, according to Johns Hopkins Medicine. Hypercalciuria can also be an inherited disease.
Struvite Stones
Struvite stones, which contain magnesium, ammonium, phosphate and calcium carbonate (struvite) crystals, often form in response to bacterial urinary tract infections that produce high levels of ammonia. Ammonia makes the urine very alkaline, which encourages struvite formation, Johns Hopkins Medicine explains. Struvite stones can grow very large, filling the cavities of the kidney. Infection remains deep inside the stone, the NYU School of Medicine states, causing recurrent infections that can seriously damage the kidney. Because the stones take on a "staghorn" shape, they're difficult to remove and usually require surgery.
Uric Acid Stones
Uric acid stones can result from a high-protein diet or diseases like gout, which raise the uric acid level. Uric acid stones can also grow quite large and, like struvite stones, fill the cavities of the kidney. Dehydration and certain genetic diseases can also raise your risk of developing uric acid stones. These stones can usually be dissolved medically and don't need to be surgically removed.
Cystine Stones
Cystine stones are uncommon; they're usually found in people with genetic metabolic disease that causes high levels of cystine, an amino acid, in the urine. They may be harder than other stones and not responsive to therapy that breaks stone into smaller pieces so they can be passed in the urine. Cystine stones can grow very large and fill the kidney, like struvite and uric acid stones.
