Alternate embodiments of an impedance spectroscopy method are disclosed for monitoring ischemic mucosal damage in hollow viscous organs. In each embodiment, a sensor catheter is placed inside a patient's hollow viscous organ. Afterwards, the catheter is electrically driven to obtain a complex impedance spectrum by causing two electrodes in the tip of the catheter to inject a current into the mucosal tissue at different frequencies, while two other electrodes measure the resulting voltages. A pattern recognition system is then used to analyze the complex impedance spectrum and to quantify the severity of the mucosal injury. Alternatively, the complex impedance spectrum can be appropriately plotted against the spectrum of normal tissue, allowing for a visual comparison by trained personnel.