Causes

Hyperoxaluria occurs when there is too much of a substance called oxalate in the urine. There are several types of hyperoxaluria:

• Primary hyperoxaluria. Primary hyperoxaluria is a rare inherited (genetic) condition present at birth. In this type, the liver doesn't create enough of a certain protein (enzyme) that prevents overproduction of oxalate, or the enzyme doesn't work properly. Excess oxalate is eliminated through your kidneys, in your urine. The extra oxalate can combine with calcium to create kidney stones and crystals, which can damage the kidneys and cause them to stop working (renal failure).

  Kidney stones form early and most often cause symptoms during childhood or adolescence. Because of the very large amounts of oxalate produced, the kidneys of many people with primary hyperoxaluria fail by early to middle adulthood. But renal failure can occur as early as infancy, while others with primary hyperoxaluria never develop kidney failure. To date, experts have identified three different genetic causes of primary hyperoxaluria.

• Oxalosis. Oxalosis occurs if you have primary hyperoxaluria and your kidneys fail. Because your body can no longer eliminate the extra oxalate, it starts accumulating — first in your blood, then in your eyes, bones, skin, muscles, blood vessels, heart and other organs. This can cause multiple problems.
• Enteric hyperoxaluria. Several intestinal diseases, including Crohn's disease and short bowel syndrome as a result of surgical procedures, increase the absorption of oxalate from foods, which can then increase the amount of oxalate excreted in the urine.
• Hyperoxaluria related to eating high-oxalate foods. Eating large amounts of foods high in oxalate can increase your risk of hyperoxaluria or kidney stones. Ask your doctor or dietitian for a list of high-oxalate foods. Avoiding high-oxalate foods is particularly important if you have enteric hyperoxaluria.