Blood flow to the rat rectum: its intramural distribution and the response to injury.

Rectal blood flow was measured in rats using radioactive microspheres. Subsequent sectioning of the material allowed the intramural distribution of that flow to be assessed. Total flow increased with increasing distance from the anorectal junction but the distribution of flow remained the same with the mucosa receiving slightly less than two thirds of the total. Injury to the mucosa, produced by a surfactant administered as a suppository, doubled total flow in areas where the damage was most severe and revealed an ability of the intramural vascular beds to react independently. Flow to the mucosa increased both absolutely and proportionately and this entirely accounted for the increase in total flow. Flow to the muscularis externa was unaltered in absolute terms, but fell as a percentage of total flow.