Hyperoxaluria is a rare condition in which the normal process of metabolism produces too much oxalic acid in a salt form called oxalate. This substance is not known to serve any particular function and is normally mostly passed through the urine, with a little sometimes retained in the gut. However, in some individuals the oxalate may combine with the calcium also normally secreted in the urine, and form stones. In hyperoxaluria, this material can deposit not only in the kidneys but throughout the urinary tract and in other organs. It may also spread throughout the body in the individual’s bloodstream.
Primary hyperoxaluria types I and II
Primary hyperoxaluria type I occurs when the liver produces too little of the enzyme alanine. This malfunction results in too much oxalate in the body which can not then be normally metabolized.
In type II primary hyperoxaluria, a different enzyme called glyoxalate reductase is missing from the liver, the absence of which also results in excessive oxalate.
There are other forms of hyperoxaluria, but the causes have not yet been determined. It is only known that both alanine and glyoxalate reductase levels are normal in the other forms.
Often, patients with primary hyperoxaluria develop kidney stones early on in life. In less severe cases, kidney stones may be the only symptom ever evidenced.
However, sometimes an individual will be over thirty years of age before diagnosis is made. By this time, kidney failure may be well on the way to occurring, and the excess oxalate may be advancing through the bloodstream causing calcium deposits in other organs.
Some warnings in hyperoxaluria are excess and frequent urination, skin ulcers, anemia, easier bone fracture, abnormal heart rhythms, and in children, the inability to grow at a normal rate.
The rate of kidney failure in primary hyperoxaluria patients is very high — fifty percent in persons under fifteen and 80 percent by age thirty.
The diagnosis of hyperoxaluria may be made through blood and urine tests, CT, X-ray and/or ultrasound. Additional assessments may include liver biopsy, cardiac echocardiograms, and bone marrow testing.
In milder cases, or those diagnosed early, hyperoxaluria may be treated with dietary changes, medications and adjustment of fluid intakes. These methods are no longer effective, however, in more severe cases. There are currently trials of experimental techniques available at many research hospitals.
Although dialysis is effective in reducing oxalate in hyperoxaluria patients for a period of time, the body is producing oxalate so quickly that the problem rarely can be addressed by dialysis alone. Thus, kidney transplant is the ultimate goal for most hyperoxaluria patients.
Signet/Mosby Medical Encyclopedia