Hyperoxaluria (called Bird's disease, after Golding Bird, who first described the condition), is an excessive urinary excretion of oxalate. Individuals with hyperoxaluria often have calcium oxalate kidney stones.
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
Type I (PH1) is associated with AGXT protein, a key enzyme involved in breakdown of oxalate. PH1 is also an example of a protein mistargeting disease, wherein AGXT shows a trafficking defect: instead of being trafficked to peroxisomes, it is targeted to mitochondria, where it is metabolically deficient despite being catalytically active. Type II is associated with GRHPR. It is also a complication of jejunoileal bypass, or in any patient who has lost much of the ileum with an intact colon. This is due to excessive absorption of oxalate from the colon.
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, may it's 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 a patient is diagnosed with primary hyperoxaluria, the siblings are at risk of the disease and should be tested as well. If his child has primary hyperoxaluria, he may want to consider genetic testing if he plans to have more biological children. Medical genetics counselors experienced in hyperoxaluria can help guide your decisions and testing.
Good in secondary hyperoxalurias. Untreated or unresponsive cases of primary hyperoxaluria have a poor outlook with chronic renal failure and severe nephrocalcinosis inevitable.
The main therapeutic approach to primary hyperoxaluria is still restricted to symptomatic treatment, i.e. kidney transplantation once the disease has already reached mature or terminal stages. However, through genomics and proteomics approaches, efforts are currently being made to elucidate the kinetics of AGXT folding which has a direct bearing on its targeting to appropriate subcellular localization. Secondary hyperoxaluria is much more common than primary hyperoxaluria, and should be treated by limiting dietary oxalate and providing calcium supplementation. A child with primary hyperoxaluria was treated with a liver and kidney transplant. A favorable outcome is more likely if a kidney transplant is complemented by a liver transplant, given the disease originates in the liver.