Methods to determine fluid filtration rates through mammalian luminal organs. In one method, the method comprises the steps of positioning a segment of a mammalian luminal organ within a device, the device configured to prevent axial flow conditions through a lumen of the segment from a first end of the segment to an opposite second end of the segment, obtaining a first segment measurement at a first time, obtaining a second segment measurement at a second time, and determining a rate of fluid filtration through a wall of the segment based upon a difference between the first segment measurement and the second segment measurement and a difference in time between the first time and the second time.