[Diagnosis of intestinal oxalate hyperabsorption in patients with idiopathic recurrent calcium oxalate urinary calculi].Urologe A. 1990 May; 29(3):148-51.U
By oral administration of 14C-labelled oxalic acid (2.2 microns Ci; 2 mg), the mean enteral oxalate absorption in 24-h urines (collecting intervals 3, 3, 6, 12 h) of 19 healthy control subjects was determined to be 8.3%. It was 14.6% (alpha less than 1%) in 20 patients with recurrent idiopathic calcium-oxalate lithiasis. The differences in absorption were most marked in the first two 3-h urines. Under the test conditions described, maximum excretion of 14C oxalate had already occurred after 3 h (55%-57%); after 6 h it was about 85%, and after 12 h 95% of the total activity in the 24-h urine. In 68% of the control subjects, the oxalate absorption values were below 10%; in 32% they were less than or equal to 15%. For the group of lithiasis patients, these findings suggest a metabolic disorder of gastrointestinal origin. In 40%, the oxalate absorption rates were clearly above 15%. The test method described is simple to carry out and can be recommended for the assessment of idiopathic calcium-oxalate lithiasis.