Methods and apparatus useful for monitoring fluid flow past a gastric restriction device using noninvasive means are described. Some methods involve the use of acoustic energy, e.g., Doppler ultrasound, to monitor the passage of fluid past the restriction device, and apparatus to detect the acoustic energy. In some embodiments the method detects a sound-producing fluid using a microphone, stethoscope, or ultrasound probe and detector combination. In some embodiments, there are described methods of using Doppler ultrasound to monitor the flow of a fluid through a stomal opening, allowing a flow condition, e.g., a flow rate, to be determined, so that a physician can accurately adjust the gastric restriction device.