Heterogeneity of macroscopic and single villus blood flow in rabbit small intestine

Heterogeneity of single villus blood flow in the small intestine was estimated from frequency distributions of 9-μm microspheres per villus in villus fields of 100-200 villi. The microspheres, which were nonradioactive, were administered, with or without 26-μm spheres in addition, by a brief injection into the left ventricle of unfasted, anesthetized rabbits. The spheres were counted and localized microscopically in cleared pieces of jejuno-ileum. It was found that gamma distributions of single villus flow would generate frequency distributions of beads per villus similar to those observed when the average villus contained up to four beads. This agreement, together with other relevant information, suggests the following view: The frequency distribution of values of single villus flow in a small area is unimodal, is skewed toward the high flow direction, has a coefficient of variation of, at most, 0.5-0.6, and is approximated by a gamma distribution. Reasons are given for believing that the coefficient of variation may be significantly smaller. The dispersion of values for total perfusion and its distribution to the layers of the intestine in small (about 25 mm²) adjacent macroscopic pieces of intestine typically had a coefficient of variation of 0.2-0.3.