Kidney stones don't all look the same. The color depends on what chemicals are in it. Most are yellow or brown, but they can be tan, gold, or black. Stones can be round, jagged, or even have branches. They vary in size from specks of sand to golf ball sized stones. In order to determine the specific type of stone, tests need to be preformed. A urine test determines levels of acidity or alkalinity using the pH scale. Blood tests help identify what substances formed the stones.
Calcium oxalate and phosphate stones: About 70% to 80% of all kidney stones are currently made up of calcium oxalate and phosphate. They are made up of a hard crystal compound. Calcium oxalate is often mixed with phosphate, but either pure calcium oxalate or calcium phosphate stones may occur. The stones can be spiky or smooth. Oxalate is found in a number of vegetables, fruits, and grains.
Struvite stones: Struvite stones account for about 13% - 18% of all stones and can vary in size and shape. They are associated with bacterial urinary infections and like urinary infections, are more common in women. In patients with struvite stones, it is important not only to remove the stone but also to prevent recurrence of the urinary infection.
Uric acid stones: These stones account for about 5% to 13% of kidney stones and are more common among men. They are smooth, brown and soft. Uric acid is produced in the liver and arises when the body breaks down certain foods, especially meats. Patients with gout, a metabolic disorder associated with high uric acid levels, are especially prone to uric acid stones.
Cystine stones: These stones are relatively rare, accounting for only about 2% in adults and 8% in children. They are yellow and usually round and smooth. The stones are produced by the breakdown of protein from your diet causing a build up of amino acid cystine. The tendency to form these stones is inherited. Children are more likely to develop cystine stones than adults.
Rare stones: Other rare stones such as xanthine or silicate may occur. Xanthine stones are caused by a rare genetic disorder and are extremely uncommon. Silicate calculi are common in some mammals, such as dogs and sheep, but extremely rare in humans. They usually have a jackstone shape.