The present application discloses a bladder monitoring system comprising a wearable bladder monitoring device (1) including securing means (27, 29) for securing the device to a subject's (40) body； a phased array (11) of ultrasound transducers (10)； and a phased array controller (13) adapted to control the phased array to direct a plurality of ultrasound beams (30, 30', 30") into the subject's body under a range of beam angles, as well as a signal processor (23) adapted to receive data pertaining to echo signals (31, 31', 31") of said ultrasound beams from the phased array. The signal processor is adapted to process said data in order to identify an edge of the subject's pelvic bone (43) proximal to the subject's bladder (41) from data pertaining to at least one of said echo signals； determine an orientation of the wearable bladder monitoring device relative to the pelvic bone based on beam angle information associated with the at least one of said echo signals； and derive bladder information from the data based on the determined orientation. A method of obtaining bladder (volume) information with such a system is also disclosed.
