Background: Anastomotic leakage is one of the most severe complications in patients undergoing esophagectomy with gastric tube reconstruction. Transection of the left gastric and gastro-epiploic artery and vein results in compromised perfusion which is seen as the major contributing factor for anastomotic dehiscence. The main objective of this prospective, observational, in-vivo pilot study is to microscopically evaluate gastric tube perfusion with Sidestream Darkfield Microscopy (SDF). Methods: Intra-operative microscopic images of gastric-microcirculation were obtained with SDF directly after reconstruction in 22 patients. Quantitative perfusion related parameters were: velocity, Microvascular Flow Index(MFI), Total Vessel Density(TVD), Perfusion Vessel Density(PVD), Proportion of Perfused Vessels(PPV) and De Backer Score(DBS). Dedicated software was used to assess parameters predictive for compromised perfusion. Results: SDF was feasible to accurately visualize and evaluate microcirculation in all patients. Velocity(μm/sec) was significantly decreased towards the fundus (p = 0.001). MFI, PVD and PVD were decreased distal of the watershed – between the right and left gastro-epiploic artery and vein – and in the fundus, compared to the base of the gastric tube(p = 0.0002). No differences in TVD and DBS were observed; because of vessel-dilation in the fundus-area. This suggests that venous congestion results in comprised inflow of oxygen rich blood and plays a role in the development of ischaemia. Conclusion: We present quantitative perfusion imaging with SDF of the gastric tube. Velocity, MFI, TVD and PPV are accurate parameters to observe perfusion decrease. Also, venous congestion is visible in the fundus, suggesting an important role in the development of ischaemia. These parameters could allow early risk stratification, and, potentially, can accomplish a reduction in anastomotic leakage.