Hyperoxaluria and oxalosis
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. Quick diagnosis and treatment of hyperoxaluria is important to the long-term health of your kidneys.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.
Commonly, kidney stones are the first sign of hyperoxaluria. Kidney stones are uncommon in childhood. Kidney stones that form in children and teenagers are likely to be caused by an underlying condition, such as hyperoxaluria. For this reason, all young people with kidney stones should have a thorough evaluation, including measurement of oxalate in the urine. Adults with recurrent kidney stones also should be evaluated for oxalate in the urine.Symptoms of a kidney stone can include the following:Severe or sudden abdominal or flank pain,Blood in the urine,Frequent urge to urinate,Pain when urinating,Fever and chills.Primary hyperoxaluria (PH) that goes untreated can eventually damage your kidneys. Over time your kidneys may stop working. For some people, this is the first sign of the disease.
Treatment will depend on the type, symptoms and severity of hyperoxaluria and how well you respond to treatment.Medications. 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. The effectiveness of diet will depend on the cause of increased levels of oxalate. Diet may include restricting foods high in oxalates, limiting salt, and decreasing animal protein and sugar (high fructose corn syrup). This may help to lower urinary oxalate in people with enteric hyperoxaluria or excess dietary intake. Dietary restrictions may not be as important for all people with primary hyperoxaluria. Follow the advice of your doctor.
Oxalate cannot be metabolized in mammals and is primarily eliminated via the kidneys as an end product of metabolism. Oxalate is freely filtered at the glomerulus and also secreted by the tubules. In all types of PH, very high urinary oxalate excretion, typically >1 mmol/1.73m2/24 hours (normal < 0.5), is observed. The urine becomes supersaturated for calcium oxalate resulting in formation of calcium oxalate complexes and crystals, which deposit in the renal parenchyma (nephrocalcinosis) and form stones in the urinary tract (urolithiasis), the clinical hallmarks of the primary hyperoxalurias (Figure 1). Progressive renal parenchymal inflammation and interstitial fibrosis from progressive nephrocalcinosis and recurrent urolithiasis along with secondary complications (urinary tract infection, obstruction) cause renal impairment, which progresses to end-stage renal failure (ESRF) over time [6–8]. Once renal function declines to a glomerular filtration rate below 30–40 ml/min per 1.73 m2 body surface area, renal excretion of oxalate is sufficiently compromised that plasma oxalate concentration rises (normal limits 1 – 6 µmol/l,) and can rapidly exceed the supersaturation threshold for calcium oxalate as levels > 30 µmol/L are reached.