Standardized ("trifixed") diet in the study of chronic malabsorption syndromes

143 patients (70 patients with Crohn's disease, 11 with ulcerative colitis, 40 with an intestinal by-pass operation, 9 with non-tropical sprue, 10 with short bowel syndrome, and 3 with other gastrointestinal disease) were studied during a metabolic regime including a fixed oral supply of 70 g fat, 800 mg calcium, and 200 mg oxalate. Faecal fat, 47Ca-absorption, 14C-oxalate absorption, and renal oxalate excretion were measured, and in the majority of patients a 14C-glyco-cholic acid breath test was also performed. 14Ca-absorption was practically identical (r = 0.92), whether determined by whole-body counting or from the accumulation of absorbed 47Ca in the skeleton of the underarm. 14C-oxalate absorption and renal oxalate excretion agreed well (r = 0.85). Steatorrhoea correlated weakly with renal oxalate excretion (r = 0.63, p less than 0.001), whereas no correlation was present between faecal fat and calcium absorption or between oxalate and calcium absorption under the constant conditions prevailing during the study. It is recommended that a "trifixed" regime with absorption studies of fat, calcium, and oxalate be undertaken previous to therapy that aims at a reduction of steatorrhoea or hyperoxaluria or an improvement of calcium absorption in chronic malabsorption syndromes, not least because therapy of these categories of patients most often continues for years.