Often, the first sign of hyperoxaluria is a kidney stone. Symptoms of a kidney stone can include:

• Severe or sudden back pain
• Pain in the area below the ribs on the back (flank) that doesn't go away
• Blood in the urine
• Frequent urge to urinate
• Pain when urinating
• Chills or fever

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.

Untreated primary hyperoxaluria can eventually damage your kidneys. Over time your kidneys may stop working. For some people, this is the first sign of the disease.

Signs and symptoms of kidney failure include:

• Decreased urine output or no urine output at all
• Feeling generally ill and tired
• Loss of appetite, nausea and vomiting
• Pale skin color related to anemia
• Swelling of hands and feet

Oxalosis in its late stages can cause a variety of complications outside the kidney, including bone disease, anemia, skin ulcers, heart and eye problems, and in children, a failure to develop and grow normally.