A system that monitors water displacement in tissue during patient therapy includes a generator supplying electrosurgical energy to tissue, a spectrometer operably coupled to the generator, and a processor communicating with the generator and with the spectrometer having a light source for exposing tissue to light and a light sensor. The light sensor is configured to sense changes in light through tissue in response to tissue treatment and communicate the changes to the processor to determine tissue hydration levels and motility. A plurality of optical fibers may be configured in an array to communicate light between the generator and tissue. An optical temperature monitor may communicate with the processor and be coupled to an optical fiber. The optical fibers may have an optic fiber distance between adjacent optical fibers. The system may be incorporated within an electrosurgical pencil or a forceps. A corresponding method of detecting hydration is also disclosed.