Clinical value of 14C-phenylacetic oil as a fat absorption test

The value of [1-14C] phenylacetic oil as a clinical test for malassimilation was evaluated in 20 normal volunteers, 20 patients with various non-gastrointestinal illnesses, 10 patients with malabsorption, and 7 patients with maldigestion. All subjects were given a test meal composed of 0.5 ml of 14C-phenylacetic oil (0.5 muCi) in 30 g of cheese and 40 g of bread. The test was simultaneously run with D-xylose. Urine was collected over a 5 h period and assayed for 14C and D-xylose. Mean urinary recovery of 14C label in volunteers was 65 +/- 15% of th: administered dose. All 10 patients with malabsorption had abnormal D-xylose excretion and excreted less than 35% of the 14C-phenylacetate. 6 of 7 patients with maldigestion excreted less than 15%, while in the 7th patient excretion of 14C label was borderline (35%). 4 of the 7 patients with maldigestion had abnormal D-xylose excretion, probably as a result of bacterial overgrowth. The procedure described is a cost-effective, simple, rapid, and safe test for fat absorption which may be conveniently run with a D-xylose excretion test.