Systems and methods are provided for assessing patient blood flow using video image processing. According to one aspect, a method of analyzing at least one blood flow characteristic of a patient includes capturing a video including a plurality of frames of an arterio-venous (AV) fistula on the patient; amplifying motion in the video to produce a motion-amplified video; determining a difference in intensity between consecutive frames in the motion-amplified video to produce a time-function of an amplitude of the optic flow representing movement in an area of interest on the patient; and determining the at least one blood flow characteristic of the patient based on the time-function.