Flow disturbance at the distal end-to-side anastomosis. Effect of patency of the proximal outflow segment and angle of anastomosis.

We investigated the flow disturbance that occurs at the distal end-to-side anastomosis. Clear plastic model end-to-side anastomoses were constructed with inlet angles of 15 degrees and 45 degrees. Flow patterns were visualized with steady and pulsatile flow using a dye-injection technique. Multiple lateral pressure measurements were made in the region of the anastomosis. A laser Doppler anemometer was used to measure near-wall velocity. Flow disturbance was minimal when the inlet angle was low and the proximal outflow segment occluded. Patency of the proximal outflow segment or a high inlet angle may result in areas of boundary-layer separation, with corresponding adverse pressure gradients at the anastomosis. These separation regions are characterized by low near-wall velocity, which may contribute to anastomotic hyperplasia.