Rapid method for the determination of fat in feces.

Study of fat absorption in a patient requires the determination of the fat content of feces. Quantitative chemical methods available for such determinations are too laborious to be practical for routine analyses. Estimation of the fat content of feces by microscopic examination, practised by many clinicians, is unreliable; this can be demonstrated by comparing the results of microscopic determinations with those of chemical analysis. The results of chemical methods expressing the fat content of a random sample of feces as percentage of dry matter are equivocal. Goiffon (7) and Frazer et al. (2) pointed out that the percentage of dry matter in feces is not necessarily constant. It may be quite variable in feces from patients with metabolic disorders or faulty absorption. The observations of Frazer and Goiffon were also confirmed in this laboratory. Balance studies are the conventional means of evaluating certain aspects of metabolism of nitrogen, calcium, etc. Only a few publications report such studies of fat absorption; yet it seems the only exact method of investigation. Estimation of fat balance is carried out as follows: The patient is kept on a diet containing a known amount of fat. The feces excreted in 24 hours are collected accurately. In a mixed sample of these feces, fat, if necessary differentiated into split and unsplit fat, is determined quantitatively. The total amount of fat consumed in 24 hours, less the amount of excreted fat, represents the amount of retained fat. This may be expressed as per cent of the amount of fat consumed. Since intestinal motility is variable, it is advisable to determine the fat balance on several consecutive days. The frequency of such determinations depends upon the magnitude of the daily fluctuations. The determination of the fat content of feces may be carried out before or after drying of the feces. There are various objections to the latter method: (1) During drying, conversions may take place by which the ratio of split fat to unsplit fat could be changed; (2) during drying, volatile fatty acids may evaporate; (3) drying takes a long time. These objections are eliminated by the determination of fat in wet feces. Therefore, we