Hyperoxaluria occurs when you have too much oxalate in your urine. Oxalate is a natural chemical in your body, and it's also found in certain types of food. But too much oxalate in your urine can cause serious problems.
Hyperoxaluria can be caused by inherited (genetic) disorders, an intestinal disease or eating too many oxalate-rich foods. The long-term health of your kidneys depends on early diagnosis and prompt treatment of hyperoxaluria.
Oxalosis happens after the kidneys fail in people who have primary and intestinal causes of hyperoxaluria, and excess oxalate builds up in the blood. This can lead to oxalate deposits in blood vessels, bones and body organs.
Symptoms
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
When to see a doctor
Kidney stones in childhood are uncommon. Kidney stones that form in children and teenagers are likely to be caused by an underlying condition, such as hyperoxaluria.
All young people with kidney stones should see a doctor for a thorough evaluation, including a test that measures oxalate in the urine. Adults with recurrent kidney stones also should be evaluated for oxalate in the urine.
Causes
Hyperoxaluria occurs when there is too much of a substance called oxalate in the urine. There are several types of hyperoxaluria:
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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.
Complications
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.
Diagnosis
Your doctor will conduct a thorough physical exam, including a medical history and discussion of your diet. Tests to diagnose hyperoxaluria may include:
- Urine tests, to measure oxalate and other metabolite levels in the urine
- Blood tests, to show kidney function as well as oxalate levels in the blood
- Stone analysis, to determine the composition of kidney stones passed or surgically removed
- Kidney X-ray, ultrasound or computerized tomography (CT) scan, to check for any kidney stones or calcium oxalate deposits
After initial testing, your doctor may recommend more tests to confirm the diagnosis and see how the disease has affected other parts of your body. These tests may include:
- DNA testing to look for inherited causes (primary hyperoxaluria)
- Kidney biopsy to look for oxalate deposits
- Echocardiogram to check for oxalate deposits in the heart
- Eye exam to check for oxalate deposits in the eyes
- Bone marrow biopsy to check for oxalate deposits in the bones
- Liver biopsy to look for enzyme deficiencies — only needed in rare cases where genetic testing does not reveal the cause of hyperoxaluria
If you're diagnosed with primary hyperoxaluria, your siblings are at risk of the disease and should be tested as well. If your child has primary hyperoxaluria, you may want to consider genetic testing if you plan to have more biological children. Medical genetics counselors experienced in hyperoxaluria can help guide your decisions and testing.
Treatment
Treatment depends on the type, symptoms and severity of hyperoxaluria and how well you respond to treatment.
Reducing oxalate
To reduce the amount of calcium oxalate crystal formation in your kidneys, your doctor may recommend one or more of these treatments:
- Medications. Lumasiran (Oxlumo) is a medicine that decreases the production of oxalate in children and adults with primary hyperoxaluria. Prescription doses of vitamin B-6 can be effective in reducing oxalate in the urine in some people with primary hyperoxaluria. Oral preparations of phosphates and citrate help prevent the formation of calcium oxalate crystals. Other medications, such as thiazide diuretics, also may be considered, depending on which other abnormalities are present in your urine.
- High fluid intake. If your kidneys are still functioning normally, your doctor will likely tell you to drink more water or other fluids. This flushes the kidneys, prevents oxalate crystal buildup and helps keep kidney stones from forming.
- Dietary changes. In general, paying attention to your diet is more important if you have enteric or dietary hyperoxaluria. Your doctor may recommend changes to your diet including restricting foods high in oxalates, limiting salt, and decreasing animal protein and sugar (high fructose corn syrup). Dietary changes like these may help to lower the levels of oxalate in your urine. But dietary restrictions may not be effective for all people with primary hyperoxaluria. Follow your doctor's recommendations.
Kidney stone management
Kidney stones are common in people with hyperoxaluria, but they don't always need to be treated. If large kidney stones are causing pain or blocking urine flow, you may need to have them removed or broken up so they can pass in the urine.
Dialysis and transplantation
Depending on the severity of your hyperoxaluria, you may eventually lose kidney function. Kidney dialysis may help temporarily, but it doesn't keep up with the amount of oxalate produced. A kidney transplant or kidney and liver transplant can cure certain inherited types of hyperoxaluria (primary hyperoxaluria).
Preparing for an appointment
For treatment of kidney stones associated with hyperoxaluria, you may start by seeing your family doctor. If you have large, painful kidney stones or stones that are damaging your kidneys, your doctor may refer you to a doctor who specializes in treating problems in the urinary tract (urologist or nephrologist).
What you can do
To prepare for your appointment:
- Ask if there's anything you need to do before your appointment, such as limit your diet.
- Write down your symptoms, including any that may seem unrelated to your condition.
- Keep track of how much you drink and urinate during a 24-hour period.
- Make a list of all medications, vitamins or other supplements that you take.
- Take a family member or friend along, if possible, to help you remember what you discuss with your doctor.
- Write down questions to ask your doctor.
For hyperoxaluria, some basic questions include:
- What's the likely cause of my symptoms?
- Are there any other possible causes?
- What kinds of tests might I need?
- Do I have kidney stones?
- What type of kidney stones do I have?
- Where are the kidney stones located? How big are they?
- What are the possible treatments for my condition?
- How can I prevent kidney stones in the future?
- I have other health conditions. How can I best manage them together?
- Do I need to plan for follow-up visits?
- Do you have any educational materials that I can take with me? What websites do you recommend?
Besides the questions you prepare in advance, don't hesitate to ask other questions during your appointment as they occur to you.
What to expect from your doctor
Your doctor may ask questions such as:
- When did you first notice your symptoms?
- Do your symptoms happen all the time or only once in a while?
- How severe are your symptoms?
- Does anything seem to help ease your symptoms?
- Does anything seem to make your symptoms worse?
- Has anyone else in your family had kidney stones?
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