In cystinuria, too much of the amino acid cystine, which does not dissolve in urine, is voided. This can lead to the formation of stones made of cystine. In patients with hyperoxaluria, the body produces too much of the salt oxalate. When there is more oxalate than can be dissolved in the urine, the crystals settle out and form stones. Shapes of various stones.
Sizes are usually smaller than shown here.
Absorptive hypercalciuria occurs when the body absorbs too much calcium from food and empties the extra calcium into the urine. This high level of calcium in the urine causes crystals of calcium oxalate or calcium phosphate to form in the kidneys or urinary tract. Calcium oxalate stones may also form in people who have a chronic inflammation of the bowel or who have had an intestinal bypass operation, or ostomy surgery. As mentioned above, struvite stones can form in people who have had a urinary tract infection. People who take the protease inhibitor indinavir, a drug used to treat HIV infection and AIDS, are at risk of developing kidney stones.