GUIDELINES [ back to index ]
19. Management of aneurysms
*1 Physical examination
Aneurysms are localised dilatations of vessels. In A/V fistulas aneurysms can be caused by access stenosis, either by pre-stenotic dilation due to increased pressure, or by post-stenotic dilatation due to increased turbulence. Aneurysmal dilatation can also be caused by excessive high flow. Pseudo-aneurysms present as expansile swellings caused by persistent subcutaneous bleeding outside the fistula vein wall or graft. They develop more frequently in grafts than in A/V fistulas and are sometimes the consequence of area puncture with weakening or destruction of the access wall but more often due to poor needling technique, resulting in the need for emergency surgical repair.
Graft pseudo-aneurysms sometimes develop at the anastomosis due to dehiscence of the suture line.
Remodelling of the vein due to increased flow leads to a dilatation of the vein. The diagnosis aneurysm refers to dilated segments, whose diameter exceeds 1.5 to 2-fold the diameter of the non-dilated access.
There is no data correlating the diameter of the aneurysm with the frequency of complications, e.g. thrombosis, infection, skin necrosis and rupture. Thus, the indication for intervention must be made on clinical grounds. In general surgical intervention is required in any aneurysm which is rapidly expanding, endangering the viability of the overlying skin, or shows signs of infection, which is especially frequent with pseudo-aneurysms.
*2 Surgical correction
Aneurysms of A/V fistulas are treated by resection of the aneurysmal segment. Sometimes an end-to-end anastomosis is possible, but often the resected segment must be bridged by a graft. Alternatively a new arterio-venous anastomosis may be created using the vein proximal to the aneurysm.
In grafts there are two kinds of aneurysms: single, large, symptomatic aneurysms and multiple aneurysms along the entire graft. The former might be treated by resection of the dilated part and interposition of a new graft allowing the remaining segments of the old graft to be used for dialysis. In cases of multiple aneurysms, a long piece of PTFE may be used to replace the aneurysmal graft, but using the arterial and venous anastomoses of the old graft 1.
*3 Ensure correct needling / Avoid area puncture
Repeated needling of the same area (area puncture) must be avoided as it may result in pseudo-aneurysm formation in a graft. Puncturing a pseudo-aneurysm may lead to rupture of the aneurysm and bleeding. Expanding pseudo-aneurysms must be treated by early and adequate surgical reconstruction of the access, additional skin flap procedure if necessary, and eventual treatment of the down-flow stenosis with which it is frequently associated.
*4 Duplex ultrasound (of aneurysms)
Aneurysms should be investigated by duplex ultrasound to distinguish between pseudo and true aneurysms, to precisely localise them, measure access blood flow, search for stenosis with either pre- or post-stenotic aneurysm as well as parietal thrombi in the aneurysm.