This paper is written by a group of reconstructive surgeons and a school of computing. The study used computational fluid dynamics to model blood flow through idealised sutured and coupled vessels, to investigate if differing anastomotic techniques affect intravascular blood flow. A computer-aided three-dimensional interactive application (CATIA), computer-aided design (CAD) and a microvascular anastomotic coupling (MAC) device were employed to obtain results of simulated anastomoses. They demonstrated how the flow patterns in the two different anastomoses vary to produce different physical properties at the anastomotic site. Based purely on the simulated data gathered, it appears clot formation may be more likely using the sutured technique. It would suggest the coupled anastomosis has less thrombogenic potential.