Figure 517

Vascular steal. Vascular steal is a common problem of dialysis access sites. The principle of steal is related to two phenomena: 1) calcification or stenosis in the inflow arterial segment proximal to an access site (so that the native artery cannot dilate to meet the increasing demands for flow volume); 2) and an outflow arterial bed in parallel to the fistula origin with higher net vascular resistance than the fistula conduit. If both of these are present, blood flow is diverted to the access site in association with a drop in perfusion pressure to the most acral tissues, the fingers. When steal is severe, trauma to the digits leads to gangrene. Several treatment strategies are available to the surgeon. The access can be "banded," or purposefully stenosed at its origin to divert flow to the ischemic site. The access can be revised using a tapered graft or the point of origin of the access can be moved more proximally in the arterial tree, in the hope of allowing full flow without diverting distal perfusion pressure. Additionally, one can perform a variety of bypass procedures to divert higher-pressure proximal blood to increase distal perfusion pressure. In severe cases, either the access or the distal digits may be sacrificed to preserve the other.

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