Urinary Oxalate Recovery after Oral Oxalic Load: An Alternative Method to the Quantitative Determination of Stool Fat for the Diagnosis of Lipid Malabsorption

Abstract

Urinary oxalate concentrations were measured in 45 patients with quiescent Crohn's disease, four patients with chronic pancreatitis and five healthy subjects after a normal oxalate (150 g/day) diet, after a high-fat (150 g/day), normal oxalate diet and after a high-oxalate (500 mg/day) diet. Urinary oxalate concentrations were significantly (P<0.05) higher in patients with Crohn's disease and steatorrhoea, but not in those with chronic pancreatitis, after administrating a high-oxalate diet compared with healthy subjects. Mean oxalate values were 19.1 mg/24 h in controls compared with 65.8 mg/24 h in Crohn's disease patients. A direct correlation (r=0.37, P<0.01) was established between faecal fats and urinary oxalate after oral oxalate load; this correlation (r=0.43, P<0.01) is closer when only patients with Crohn's disease are considered. The study, therefore, confirmed a correlation between steatorrhoea and hyperoxaluria in patients with Crohn's disease; however, the high percentage of false positive results limits the use of urinary oxalate concentrations as a reliable indicator of lipid malabsorption. It is concluded that, at present, measurement of urinary oxalate cannot be recommended as a valid alternative to the Van de Kamer method for diagnosing lipid malabsorption.