Intelligent Ureteral Stent Placeable via Standard Procedure for Kidney Pressure Telemetry: An Ex-Vivo Study.

Abstract

This paper reports the first telemetric ureteral stent compatible with common placement procedure, enabling wireless sensing and detection of ureteral obstruction and resultant kidney swelling known as hydronephrosis at an early stage. This sensor-integrated "intelligent" ureteral stent is prototyped via the design and fabrication approaches that raise the practicality of the device and tested in a harvested swine kidney-ureter model ex vivo. Leveraging a polymeric double-J stent and micro-electro-mechanical systems technology, the intelligent stent is built by embedding micro pressure sensors and a radiofrequency antenna, forming a resonant circuit that enables wireless kidney pressure monitoring in an operating frequency of 40-50 MHz. The stent device is entirely packaged with Parylene-C for both biocompatibility and electrical insulation of the device in order to function in the real environment including urine, an electrically conductive liquid. A comparison between the results measured in in-vitro and ex-vivo settings show a good match in the sensitivity to applied pressure. In particular, the ex-vivo test in the kidney-ureter model pressurized with artificial urine in a cycled manner demonstrates wireless pressure tracking with a response of 1.3 kHz/mmHg, over pressures up to 37 mmHg that well covers a range of pressure increase known for chronic obstruction. This testing is enabled by the prototype placement into the ex-vivo model using the standard stenting technique and tools without noticeable functional degradation or failures, showing potential compatibility of the device with today's clinical need as a ureteral stent.