The project goal is to develop an instrument for real-time monitoring of renal function for early detection of renal failure. Studies will be conducted with a phantom and with human subjects to validate the instrument's effectiveness. If successful, the project is expected to provide the means for early identification and treatment of renal failure and, thereby, prevent permanent kidney damage or death in patients at high risk of developing acute renal failure. The development of the instrument is made possible by recent research at Massachusetts General Hospital (MGH) and at Aurora Technologies Corporation (Aurora). MGH has demonstrated the efficacy of measuring renal function by monitoring (externally) the rate of disappearance of a radiolabeled agent which is cleared almost exclusively by glomerular filtration from extracellular space. Aurora's new semiconductor detector technology eliminates the need for bulky detection devices operating at high voltage and makes feasible the manufacture of a compact, self- contained instrument which will be worn in a cuff on a patient's arm. With no tubes nor wires attached, the instrument will measure the clearance of the radiolabeled agent without piercing the skin, thus, providing real-time measurement of renal function and reducing the need for repeat blood samples.