The measurement of dialysis access recirculation.

The measurement of dialysis access recirculation has important diagnostic implications. Recent recognition that its traditional means of measurement is fraught with the potential for substantially overestimating access recirculation requires that we alter current practice. Most of the potential error in the measurement can be overcome by using an arterial rather than a venous specimen for the "systemic" sample. For practical purposes, such a sample can be drawn from the dialysis afferent (arterial) line as long as it is done in a manner that minimizes both contamination by recirculated blood as well as the increase in blood urea nitrogen that occurs when the arteriovenous blood urea nitrogen gradient is dissipated by slowing or stopping dialysis.