Non-invasive endoscopic technique to assess gastrointestinal perfusion

Changes in mucosal blood flow may occur in many gastrointestinal disorders, but assessment is impossible without a non-invasive in vivo technique. We have compared endoscopic laser Doppler (LD) with oxygen electrode (OE) measurements in a dog isolated colon preparation, using variable perfusion measured with an electromagnetic flow probe. At maximum flow, LD measurements were made at three sites to compare mucosal with serosal readings. Flow rate was varied (1-38 ml/min) and measurements of microcirculatory flux obtained using LD, and of oxygen tension using a serosal OE. A progressive trend towards increasing flux was demonstrated from caecum to rectum-serosa: 46.8 +/- 18.7 V (caecum), 52.6 +/- 17.9 V (mid-colon) and 61.3 +/- 17.6 V (rectum). A parallel trend was observed in mucosal values: 41.1 +/- 18.2 V (caecum), 45.7 +/- 15.2 V (mid-colon) and 54.1 +/- 15.1 V (rectum). At all sites, serosal and mucosal values were not significantly different (Student's t test). LD serosal values correlated significantly with EM flow (r = 0.544, 0.01 greater than P greater than 0.001). A similar linear correlation was found between OE and EM flow (r = 0.65, P less than 0.001). Oxygen tension measurements varied as expected with microcirculatory flux (r = 0.441, 0.02 greater than P greater than 0.01). Endoscopic LD assessment of colonic microcirculation accurately reflects changes in blood flow.