Expanded polytetrafluoroethylene grafts for portal vein replacement: use of omentum wrap to promote graft healing.

This study was designed to reexamine the healing process of expanded polytetrafluoroethylene (EPTFE) grafts with standard porosity (30 microm) and high porosity (60 microm) in portal vein replacement, and to evaluate the effect of an omentum wrap, which has certain functions that promote healing, on graft healing. These grafts, either wrapped by the omentum or not, were placed as portal vein replacements in 24 mongrel dogs. After 1 month, the grafts were retrieved and examined for patency, thrombus-free areas, thickness of the pseudointima, and the total number of cells growing into the graft wall. There were no statistical differences in the patency rates. The high-porosity grafts had a significantly larger thrombus-free area, a thicker pseudointima, and a larger growth of cells than the standard-porosity grafts. The omentum wrap significantly increased the thrombus-free area and stimulated a larger growth of cells in both grafts. The high-porosity grafts plus omentum demonstrated a thrombus-free area of 82.2% vs 27.3% in the standard-porosity grafts. In addition, the migration of fibroblasts and macrophages was most evident in the high-porosity grafts wrapped by the omentum. In conclusion, graft healing enhancement was observed in the high-porosity EPTFE grafts wrapped by the omentum. It is thus suggested that transmural cellular migration plays an important role in the process of graft healing.