Autoregulation of intestinal blood flow: physiology and pathophysiology.

This paper reviews the published work on the autoregulation of intestinal blood flow. Under certain experimental conditions, total intestinal blood flow is autoregulated at arterial pressures varying between 80 and 160 mmHg. Flow autoregulation is more pronounced in the villus circulation than in the vascular bed of the intestinal muscle layers. The autoregulatory vascular adjustments occur in the small precapillary vessels. Some observations have suggested that not only flow but also mean capillary hydrostatic pressure is autoregulated. The importance of this mechanism is that even a small increase in mean capillary pressure could induce considerable filtration of fluid across the huge capillary area of the intestinal mucosa. During flow autoregulation the efficiency of the intestinal countercurrent exchanger increases, which is probably an important factor in explaining the villus ulcerations that develop during arterial hypotension.