A device, system and method for detecting bile and blood are provided. The device may comprise a housing having a gap through which in-vivo fluids may flow, illumination sources on one side of the gap, a light detector which is facing the illumination sources and is positioned on the opposite side of the gap for detecting light which passes through the in-vivo fluids, and a transmitter to transmit the detected signals generated according to the detected light. The system may further comprise a receiver to receive the detected signals transmitted by the transmitter, and a processor. The method may comprise comparing the detected signals with a predetermined threshold calculated from the transmission spectra of bile and of blood and determining the presence and/or concentration of bile and blood in-vivo.
