Endoscopic Measurements of Canine Colonic, Mucosal Blood Flow Using Hydrogen Gas Clearance

We have examined the feasibility of hydrogen (H₂) clearance for endoscopic measurements of colonic mucosal blood flow in anesthetized dogs. In 6 animals, measurements of H₂ clearance did not differ significantly in different regions of the sigmoid colon and they were highly reproducible (p < 0.001) on different days. In a total of 12 dogs, measurements of H₂ clearance correlated closely with those obtained using radioactive microspheres under resting conditions and, in 4 dogs, during infusion of vasopressin (slope = 0.94, p < 0.001). In 8 dogs, ligation of the major arteries supplying the sigmoid colon resulted in an acute 60% decrease in sigmoid mucosal blood flow (p < 0.001); however, in 5 animals that survived the procedure, mucosal blood flow returned nearly to control levels as early as 3 days after operation. Endoscopic H₂ clearance thus appears to be feasible for measuring mucosal blood flow in the colon. Serial measurements of H₂ clearance may prove useful in characterizing the role of mucosal blood flow in the pathogenesis of various forms of human colonic disease.