Noninvasive, real-time monitoring of renal function: the ambulatory renal monitor.

The objective of this study was to develop a method for the noninvasive, continuous and real-time monitoring of renal function. A radiation detector attached to a miniature data logger was used to monitor the clearance of the glomerular filtration agent 99mTc-diethylenetriaminepentaacetic acid from the extracellular space. The rate constant (k) for this clearance showed an excellent correlation with simultaneous glomerular filtration rate (GFR) measurements performed with a standard 125I-iothalamate clearance technique in 50 patients. Moreover, the reproducibility of the k measurement for an individual or a population was superior to the GFR measurement performed with the standard clearance technique. The procedure was also used to monitor the renal function in patients at risk for acute renal failure during angiography or in the intensive care unit under noninvasive and near real-time conditions. The results show that the technique detects rapid changes in renal function with a resolution time of 5 min in patients with normal renal function and 15 min in patients with severely impaired renal function. Since the method is noninvasive, precise and provides a near real-time measurement of GFR, its use may lead to an improvement in the management of patients in situations in which a rapid measurement is the major concern.