A surgical system used to determine if a vessel is within a region proximate to a working end of a surgical instrument includes at least one light emitter configured to emit light of two different wavelengths. The system also includes at least one light sensor disposed opposite the at least one light emitter, the at least one light sensor configured to detect light at the two different wavelengths and to provide a signal having a pulsatile and a non-pulsatile component for each wavelength. The system further includes a controller coupled to the at least one light sensor and configured to determine and indicate if the vessel is a ureter within the region proximate to the working end of the surgical instrument based on a ratio and a symmetry of a dip in the non-pulsatile component.
