A simple new method to calculate small intestine absorptive surface in the rat.

The rat is an established model for studying intestinal adaptations following abdominal surgery. In the study of functional and morphological adaptations of the small intestine, it is helpful to estimate the mucosal surface area. In order to simplify measurements and calculation we developed a new mathematical model for calculation of the mucosal surface area on histological sections. In contrast to other methods, it requires only cross-sections of small intestine and includes the measurement of only three histological parameters: length and width of villus and width of crypt. The new approach was compared with the most commonly used procedures, the Harris and the Fisher-Parsons methods, under experimental conditions. An animal study including single-pass perfusion, fixation, staining and subsequent histomorphometry of jejunum and ileum using these different methods was performed. The new method showed the least work and presented no significant differences compared with the precise Harris method. In conclusion, the method described is an adequate tool to estimate the mucosal surface area with less work and with comparable results to established methods. The less-complex method may be a valuable tool in experimental research of small intestine adaptations in rats.