Methods for the analysis of intestinal function

The intestinal tract, an organ of considerable complexity, requires application of numerous techniques for analysis of its physiology and perturbations by toxicologic agents. This review describes the methodology of importance in analysis of the absorptive function of the intestine and the transit of intestinal contents. Methods for studying absorption are categorized according to the technique for administering the test substance such as inclusion in the diet or by gastric and intestinal placement and the method of quantitating the degree of absorption such as determining the appearance of a test substance in systemic fluids or its disappearance from its site of administration in the intestine. In vitro techniques which have no in vivo analogs, such as the use of the everted sac, are briefly described and their limitations emphasized. Procedures of importance in the clinical diagnosis of malabsorption or in the experimental analysis of absorptive function in man are included and distinguished from techniques used in animal models. In addition, methods for studying aspects of gastrointestinal motility, including the use of luminal markers and analysis of the contractile and electrical activity of intestinal smooth muscle, are reviewed.