[Aneurysms in arterio-venous synthetic shunts after dialysis therapy. Morphology and pathogenesis].

Synthetic grafts are used as arterio-venous fistulae (shunts) for dialysis therapy of patients with chronic renal insufficiency. Today grafts made of PTFE (polytetrafluorethylene) are commonly used. Grafts with diameter of 6 mm are implanted subcutaneously. In rare cases stenosis or thrombosis cause explantation of the grafts. Our results, obtained on 10 samples taken from surgery or autopsy, revealed that the main causes for graft explantation are destructions and perforations of the graft's wall caused by needle puncturing during dialysis. Single defects of the implants wall ranging from 200-500 micro m, and in some cases up to 1,5 mm are "repaired" by connective tissue. But greater defects cannot be compensated and are insufficiently covered by a network of loose connective tissue. These zones are under the predominated sites for development of false prosthetic aneurysm, which show parallel to posttraumatic aneurysms of vessels. Prosthetic aneurysms up to diameters of 3,2 cm were seen. Suitable choice of puncturing sites and puncturing technique can help to avoid destruction of the synthetic material.