Estimation of fat absorption from single fecal specimens using 131I-triolein and 75Se-triether. A study in rats with and without induced steatorrhea.

The simultaneous use of 131I-triolein and 75Se-triether, a nonabsorbable marker, in a single oral dose to estimate fat absorption from incomplete fecal collections was tested in rats with and without induced steatorrhea. The results in normal rats showed that analysis of single stool samples allows a valid estimate of fat absorption as defined by the balance study based on the total fecal recovery of 131I. However, in the few normal rats with poor absorption, the absorption values from successively excreted stools showed a tendency to increase. Similar findings were obtained from biliary fistula rats with marked steatorrhea. No evidence of different intestinal transit rates of test fat and marker was observed in bile-diverted rats, thus suggesting that the observed inconsistency in fat absorption values from different stool specimens reflects intraprandial differences in the absorption of fat. Studies on rats subjected to intestinal ischemia do not support the suggestion of others that separation of fat and triether will occur if a mucosal defect is involved as the cause of fat malabsorption. It is concluded that this dual isotope technique may be of value in the clinical estimation of fat absorption, as it offers important technical advantages over conventional fat balance studies.