Oxalate (24 hour urine)

Oxalate (Oxalic acid) is an organic acid that is a natural end product of metabolism. Exogenous (dietary) sources of oxalate include rhubarb, spinach, nuts and chocolate; ascorbic acid (Vitamin C) is a precursor of oxalate and excessive vitamin C intake can result in increased oxalate excretion. Endogenous synthesis of oxalate occurs in the liver and enzyme deficiencies in this metabolic pathway give rise to the rare inherited disorders Primary Hyperoxaluria (PH) type 1, 2 and 3. Urinary oxalate excretion is markedly elevated in patients with PH. Secondary causes of raised oxalate excretion include high dietary intake of oxalate / oxalate precursors and fat malabsorption. Approximately 90% of oxalate is excreted via the kidneys; when urine oxalate concentration is increased there is increased formation of insoluble calcium oxalate, giving rise to kidney stones.