Methods and systems for monitoring an organ of interest within a patient use one or more sensors to obtain one or more signals indicative of one or more of blood being provided to the organ of interest, blood being received from the organ of interest, and blood present in the organ of interest. Changes in an amount of blood being provided to the organ of interest, an amount of blood being received from the organ of interest, and/or an amount of blood present in the organ of interest are monitored based on changes in the obtained signal(s). Such methods and systems can be used to detect dysfunction of the organ of interest or tumor growth in the organ of interest, but are not limited thereto.