Non-invasive diagnosis and monitoring of chronic kidney disease by reverse iontophoresis of urea in vivo

BACKGROUND: Reverse iontophoresis uses a small current to extract molecules and ions through the skin. The aim of the study was to determine whether reverse iontophoresis of urea can be used (i) to diagnose and monitor non-invasively chronic kidney disease (CKD), and (ii) to track urea levels closely during a hemodialysis session. METHODS: A current of 0.8mA was applied for 2h in 10 healthy volunteers, in 9 patients with CKD, and in 10 patients undergoing hemodialysis. Urea fluxes extracted by reverse iontophoresis and urea concentrations in the blood were measured. RESULTS: Extracted urea fluxes discriminated healthy volunteers from patients with CKD within 90min. A non-invasive measure of blood urea concentrations can be achieved after 120min. A urea reservoir in the skin interferes with the extraction and a pre-hemodialysis "depletion" period is required. Mild and transient sensation and erythema induced by iontophoresis were significantly lower in the CKD group. Gelling the formulation of the iontophoresis reservoir gave similar results to those obtained when using a simple aqueous solution. CONCLUSIONS: Reverse iontophoresis can be used to non-invasively diagnose individuals with CKD and to monitor urea concentrations in blood.