Failure of allopurinol to modify urinary composition in enteric hyperoxaluria

Conventional treatment of enteric hyperoxaluria (EHO) consists of dietary restriction of oxalate and fat and correction of its underlying cause whenever possible. Recent work suggests that allopurinol reduces the incidence of urolithiasis and the urinary excretion of both oxalate and uric acid in patients without intestinal disease. We have assessed the effect of allopurinol, 300 mg daily for 2 weeks, on urine biochemistry in patients with EHO due to small bowel Crohn's disease and/or resections. Compliance with treatment was confirmed by a fall in plasma uric acid in every patient. Allopurinol failed to alter 24 h urinary oxalate excretion or oxalate concentration. There were also no significant changes in the urinary excretion of glycollate (like oxalate, a breakdown product of glyoxylate), citrate, magnesium or calcium, each of which was at the lower end of the normal range before and during treatment with allopurinol. It appears unlikely that allopurinol will prove useful in the prevention of urolithiasis in patients with EHO.