Silicon and polymer-based technologies were developed in order to reach the industrial fabrication of disposable, mass-fabricated microsensors for the urea detection in liquid phase. The detection principle is based on pH-sensitive chemical field effect transistor (pH-ChemFET) microdevices. In order to realize an urea-sensitive enzymatic field effect transistor (urea-EnFET), studies involve the integration of an urease-based enzymatic layer by ink jet printing techniques, the packaging into a specific flow cell compatible with the liquid phase measurement, and the development of urea-EnFET/pH-ChemFET differential analysis technique. Thus, the urea detection properties were studied in EDTA-based and dialysate solutions, evidencing good sensitivity in concentration ranges appropriate to human kidney failure. Finally, the whole analysis system was successfully tested for the continuous monitoring of urea in artificial dialysis conditions.