Hydraulic expansion facilitates remodeling of arteriovenous fistulas without increasing venous intimal hyperplasia in rabbits

BACKGROUND: An arteriovenous fistula (AVF) is considered essential for chronic hemodialysis. OBJECTIVE: To determine the effects of hydraulic expansion on the intimal hyperplasia of an AVF. METHODS: We divided 12 healthy male New Zealand white rabbits into a control group (vein without special handling and direct anastomosis with an artery, n = 6) and a hydraulic expansion group (vein dilated by hydraulic pressure before anastomosis, n = 6). Histopathomorphology was examined with hematoxylin and eosin staining and immunohistochemistry. Analysis of covariance (ANCOVA) was used to compare the data between the groups. RESULTS: Immediately and 1 day after surgery, the diameter of the fistula vein in rabbits in the hydraulic expansion group was significantly larger than it was in the control group (P = 0.02 and 0.03 respectively), but not on subsequent days. After hydraulic expansion and before construction of the fistula, the wall of vein was noticeably thinner on macroscopic observation, and the anterior and posterior walls were indistinguishable. At 3 weeks after surgery in the hydraulic expansion group, cells in the vein wall were disordered, there were fewer elastic fibers, tissues from the endothelium to tunica externa were less dense, and there was less extracellular matrix than in the control group. Expression of connective tissue growth factor in the hydraulic expansion group was significantly less than that in the control group (P = 0.01). No differences were found in intimal thickness or immunohistochemistry scores for transforming growth factor-β1 between the groups. CONCLUSION: Hydraulic expansion did not increase intimal hyperplasia of an AVF, but facilitates remodeling of AVFs in rabbits.