What is hyperoxaluria?
Hyperoxaluria is a condition that occurs when there is too much oxalate in your urine. Oxalate, a natural chemical in your body and also contained in some foods, is normally eliminated from the body through the kidneys in the urine (and can also be eliminated through stool).
Too much oxalate in the body can cause some serious health problems. An excess amount of oxalate can combine with calcium in the urine and cause kidney stones and crystals to form. Recurrent kidney stones and crystals can damage the kidney and lead to kidney failure. In addition, if the kidneys begin to fail and can’t eliminate excess oxalate, eventually oxalate crystals can build up in other areas of the body and cause bone disease; blood problems (anemia); heart, skin and eye problems and growth and development problems in children. When oxalate builds up in the body’s tissues, the condition is called systemic oxalosis.
Who gets hyperoxaluria?
Symptoms of hyperoxaluria can develop anytime from infancy to later adulthood (over 70 years of age). The most common initial symptom is usually kidney stones. However, initial symptoms can vary from mild to severe. In some patients, kidney failure is the first symptom.
It is estimated that about 5,000 patients in the United States have primary hyperoxaluria. Patients with primary hyperoxaluria typically develop kidney stones by the age of 20. If babies develop primary hyperoxaluria (rare), the condition tends to be severe. About 50 percent of patients with primary hyperoxaluria experience kidney failure by age 15; about 80 percent will experience kidney failure by age 30. Older children and adults who develop primary hyperoxaluria tend to have better outcomes. The course of the condition varies with each individual.
It is estimated that about 200,000 to 250,000 people in the United States have secondary hyperoxaluria (see "causes" section).
Symptoms and Causes
What are the symptoms of hyperoxaluria?
Kidney stones are usually the first symptom. Signs and symptoms of kidney stones include:
- Pain in the lower back or side of body. Pain can start as a dull ache that may come and go. Pain can become severe and result in a trip to the emergency room.
- Nausea and/or vomiting with the pain.
- Blood in the urine.
- Pain when urinating.
- Unable to urinate.
- Feeling the need to urinate more often.
- Urine that smells bad or looks cloudy.
What causes hyperoxaluria?
There are two types of hyperoxaluria, primary hyperoxaluria and secondary hyperoxaluria.
- Primary hyperoxaluria is a rare, genetic (inherited) disorder of the liver in which the liver either does not produce enough enzymes to prevent the overproduction of oxalate or the enzymes do not work properly. There are three subtypes of primary hyperoxaluria, each of which involves a genetic defect of a different enzyme in the liver and all of which play a role in the overproduction of oxalate.
- Secondary hyperoxaluria is a condition in which excess oxalate is absorbed into the gastrointestinal (GI) tract and then excreted in the urine. The reasons for increased absorption can be due to eating foods that contain high levels of oxalates or having medical conditions that cause the GI tract to absorb more oxalate (such as Crohn’s disease, inflammatory bowel disease, gastric bypass and other disorders in which nutrients are not properly absorbed).
Diagnosis and Tests
How is hyperoxaluria diagnosed?
In addition to a physical exam, medical history, and diet history, typical tests used to diagnose hyperoxaluria include:
- Urine tests to measure levels of oxalate and other specific enzymes; urine is also checked for crystals
- Blood test to measure the amount of oxalate in blood.
- Scans (X-rays, ultrasound, and/or CT) of the kidneys and urinary tract to check for kidney stones or calcium oxalate crystals.
If kidney stone(s) are found and surgically removed or passed without surgery, an analysis of the makeup of the stone may be done.
Other tests may be done to determine if there are oxalate deposits in other organs and tissues. These tests include:
- Kidney and bone marrow biopsies to look for oxalate deposits in these tissues
- Echocardiogram to look for oxalate deposits in heart tissue
- Eye exam to check for oxalate deposits in the eye
- CT to detect calcium or oxalate deposits in the bowel wall, muscle, and arteries
If your doctor suspects primary hyperoxaluria, he or she may also do genetic testing to determine if you have a gene mutation.
Management and Treatment
How is hyperoxaluria treated?
The goal of treatment is to lower the level of oxalate in the body and prevent calcium oxalate crystals from forming in the kidneys and other body tissues. Certain treatments are recommended for primary hyperoxaluria (PH) and for secondary hyperoxaluria (SH). These treatments include:
- Taking medications.
- For patients with PH, medications options include a prescription dose of vitamin B-6 (pyridoxine) to reduce the oxalate level; also thiazide diuretics for a specific subtype of PH.
- For patients with either PH or SH, medication options include oral doses of potassium citrate or the combination of orthophosphate and magnesium to prevent calcium oxalate crystals from forming.
- Drinking fluids. For patient with either PH or SH, increase your daily intake of water to 2.5 to 3 liters/day. Fluids help to continuously flush oxalate from the kidneys, which help prevents oxalate buildup and stone formation.
- Changing your diet. If secondary hyperoxaluria is the cause, your doctor may recommend limiting salt intake, decreasing sugar intake, eating less animal proteins (milk, egg, and fish), and avoiding foods high in oxalate levels such as spinach, bran flakes, rhubarb, beets, plums, chocolate, strawberries, tofu, almonds, potato chips, french fries, nuts and nut butters. Excessive intake of Vitamin C should be avoided. Be cautious of the “juicing” health fad. Many of the food products used in juicing mixtures are high oxalate-containing foods. Adding calcium-rich foods to meals helps reduce oxalate levels. Calcium naturally binds to oxalate; eating calcium-rich foods at meals helps with this binding and removal of oxalate through the stool rather than through urine. (Note: Dietary changes do not significantly help manage primary hyperoxaluria since this is an inherited form and is due to a defect in your genes.)
If a kidney stone is present, the stone may be able to pass on its own by drinking a lot of water. If your kidney stone does not pass on its own, a procedure may be performed to remove the stone. Possible procedures include shock wave lithotripsy, ureteroscopy, or percutaneous nephrolithotomy. Your doctor will discuss which method is best for your situation if stone removal is needed.
If hyperoxaluria is severe, your kidneys may stop working. When this happens, kidney dialysis or organ transplantation (kidney or liver-kidney combination transplant) will be needed. The type of transplant depends on the specific type of primary hyperoxaluria. There is limited data on the role of transplant for patients with secondary hyperoxaluria. Your doctor will discuss all treatment options with you.
Who should be screened for hyperoxaluria?
The following patients are at greater risk of hyperoxaluria and therefore should be evaluated for this condition:
- All children who are diagnosed with kidney stones.
- All adults who have recurring kidney stones.
- All patients, regardless of age, who have a family history of kidney stones.
- All patients, regardless of age, in whom calcium deposits are found in the kidney.
- Any patient with renal failure of unknown cause.
Genetic testing should be offered if your brothers or sisters have been diagnosed with primary hyperoxaluria. (Parents may not have symptoms of the condition but can pass the genetic defect to their children, and one or more children may develop the condition.)
Can hyperoxaluria be prevented?
If you have been diagnosed with primary hyperoxaluria (an inherited condition), hyperoxaluria cannot be prevented. If someone in your family has been diagnosed with hyperoxaluria, you can be screened for this gene defect. Treatment can be started before any symptoms or organ damage occurs. To reduce the chance of recurrent kidney stones, chronic kidney disease or end-stage kidney disease, patients with secondary hyperoxaluria should follow the treatment plan outlined by your doctor.
Outlook / Prognosis
What’s the outlook (prognosis) for someone with hyperoxaluria?
Untreated hyperoxaluria can eventually lead to kidney damage and even kidney failure and death. Depending on its severity, dialysis and organ transplant may be needed. In addition, oxalate crystals can build up in other areas of the body and cause bone disease; blood problems (anemia); heart, skin and eye problems and growth and development problems in children. Because of these complications, prompt diagnosis and early treatment is important to the prognosis.
There is no cure for primary hyperoxaluria. The goal is to protect the kidneys by preventing the development of kidney stones and prevent calcium oxalate from forming and depositing in other body tissues.
Your doctor will talk with you about your particular type of hyperoxaluria and provide a treatment plan to best manage your condition.
It is critical that people living with hyperoxaluria follow their doctor’s treatment plan and have regular clinical exams with their urologist or primary care provider.
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