The fractional intestinal absorption of oxalate and calcium was investigated by isotope techniques in 20 normal subjects and in 12 idiopathic calcium oxalate stone formers. The greatest amount of 14C-oxalate was excreted during the first six hour period in controls as well as in stone formers. The stone formers had a greater intestinal uptake of oxalate (11 +/- 5.1%) than the controls (6.2 +/- 3.7%; p less than 0.01). There was no significant relationship between the fractional absorption of oxalate and the total urinary oxalate excretion. The stone formers also had a higher fractional uptake of calcium compared to the controls (55 +/- 11% vs. 47 +/- 9.1%; p less than 0.05). There was a positive relationship (r = 0.47) between the urinary excretions of calcium and oxalate in the stone formers. During these conditions no correlation could be demonstrated between the fractional absorptions of oxalate and calcium, neither in the stone formers nor in the controls. In conclusion, patients with recurrent formation of calcium oxalate containing stones appear to have an enhanced intestinal uptake of both oxalate and calcium. This disturbance could be of primary pathogenic importance for their stone forming propensity.
Thirty-one calcium stone patients were treated with 300 mg allopurinol daily during a mean follow-up period of 2 years. They were also given advice on diet and fluid intake. The effects on the recurrence rate of stones were compared with the effects on the recurrence rate in 43 calcium stone patients who were given similar advice on diet and fluid intake but were not treated with allopurinol. In both groups there was a reduction in the recurrence rate but no difference between patients treated with allopurinol and the control group. Some patients with only hyperuricosuria prior to treatment seemed to benefit from allopurinol treatment, whereas those with hypercalciuria continued to form stones with the same frequency. Allopurinol treatment in calcium stone disease appears less effective than treatment with thiazides, magnesium hydroxide or orthophosphate.
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