[Hemodialysis access recirculation].

Vascular access recirculation (R) allows the evaluation of the adequacy of the extracorporeal blood circuit in dialysis patients. The test verifies the correct needle position in patients with arterovenous fistulae (AVF) and the effective function of central venous catheters. In clinically uncomplicated native fistulae, a normal R test could avoid more complex procedures like blood flow measure or angiography. The AVF recirculation has two components, vascular access recirculation (AR) and cardiopulmonary recirculation (CPR). While the first phenomenon is well known, the second remained undetected for many years resulting in wrong R calculations with false positives. Using the correct formula, the great majority of AVF resulted in zero recirculation. The presence of R reduces the dialysis efficiency to critical levels, mainly in unsuspected cases. Among the numerous available R tests, the urea test is the oldest and historically the most commonly used method, but unfortunately it is labor intensive, with low sensitivity and specificity and with delayed results. The "ultrasound dilution"method is considered the gold standard, easy to perform, with good repeatability, but it is expensive requiring a specific device. Finally, the glucose infusion test (GIT) is a new low-cost test with immediate results and a very low detection limit, with good repeatability and high specificity and sensitivity.