Hyperoxaluria

The inborn errors of glyoxalate metabolism that cause increased endogenous oxalate biosynthesis are inherited in an autosomal recessive manner. In type I (primary hyperoxaluria) there is increased glycolate excretion as well as hyperoxaluria. In type II, l-glycerate excretion is increased. In both types, calcium oxalate stone formation occurs.

The prognosis is poor owing to widespread calcium oxalate crystal deposition in the kidneys. Renal failure typically develops in the late teens or early twenties. Successful liver transplantation has been shown to cure the metabolic defect in type I hyperoxaluria.

Causes of Hyperoxaluria

Much more common causes of mild hyperoxaluria are:

• excess ingestion of foodstuffs high in oxalate, such as spinach, rhubarb and tea
• dietary calcium restriction, with compensatory increased absorption of oxalate
• gastrointestinal disease (e.g. Crohn's), usually with an intestinal resection, associated with increased absorption of oxalate from the colon.

Dehydration secondary to fluid loss from the gut also plays a part in stone formation.